FAO Fish Culture in Undrainable Ponds

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Title: Fish Culture in undrainable ponds - A manual for extension...

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FAO FISHERIES TECHNICAL PAPER 325

Fish culture in undrainable pondsA manual for extension

TABLE OF CONTENTS

byDilip Kumar

Central Institute of Fisheries EducationIndian Council of Agricultural Research

Versova, Bombay, India

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M-44ISBN 92-5-103139-8

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FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome,© FAO

PREPARATION OF THIS DOCUMENTThis document has been prepared within the framework of the Regular Programme activities of the InlandWater Resources and Aquaculture Service of the Fishery Resources and Environment Division. Theprimary objective of this document is to assist extension workers and other field personnel engaged infish culture in undrainable ponds to increase production through the application of improved culture

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technology.

The original manuscript was prepared by Mr. Dilip Kumar of the Central Institute of Fisheries Education,Bombay, India, based on the Indian experience of fish culture in undrainable ponds, and it was edited byMr. P.C. Choudhury. It is hoped that this manual will be useful to extension workers and fish farmers inareas where fish ponds are not drainable.

Kumar, D.

Fish culture in undrainable ponds. A manual for extension.

FAO Fisheries Technical Paper No. 325. Rome, FAO, 1992. 239 p.

ABSTRACT

This manual deals with the methods of freshwater fish culture in undrainableponds as practised in India. The manual is primarily meant for extension workersand aquaculture training institutions. It outlines the basic principles of fish cultureand the characteristics of undrainable ponds. The systems of composite carpculture and composite carp culture-livestock farming have been described.Methods of improvement of existing ponds and construction of new ponds havebeen included. The suitable species for culture, procurement of their seed,stocking ratios of various species under composite culture, etc., have beendiscussed. Pond management, both pre-stocking and post-stocking, including fishhealth management and management of common hazards have been dealt with. Italso contains information on marketing and economics of fish culture inundrainable ponds.

Distribution:

FAO Fisheries DepartmentInland Waters - GeneralFAO Regional Fisheries OfficersAuthor

ACKNOWLEDGEMENTSSincere gratitude is expressed to the Fisheries Department of the Food and Agriculture Organization ofthe United Nations for suggesting and sponsoring the preparation of this manual and to the IndianCouncil of Agricultural Research (ICAR), Ministry of Agriculture, Government of India, for kindly permittingme to take up this job. The author is indebted to Drs. R.M. Acharya, P.V. Dehadrai, and M.Y. Kamal,ICAR Headquarters, New Delhi, who were instrumental in obtaining this permission. Sincere support,encouragement, valuable guidance and never-ending help is extended to Drs. V.R.P.Sinha, S.D. Tripathi,and A.G. Jhingran. The author extends his heartfelt thanks to Dr.N.G.S. Rao, Mr. M. Ranadhir, Mr. H.A.Khan, Mr. B.B. Satpathy and Dr. B.N. Singh for critically going through the relevant chapters of themanuscript. Finally, he is glad to acknowledge the tremendous help provided by his colleagues Mr.Kuldeep Kumar, Dr.S.K.Sarkar, Mr. C.D. Sahoo, Dr. S.N. Mohanty, Dr. N. Sarangi, Mr. M.S.Tantia, Mr.R.K.Dey, Mr. A.K. Sahoo, Mr.S. Ayyappan, Mr. C.S. Purushothaman, Dr. K. Jankiram, Mr. D.Narayanswamy, Mr. B.K. Mishra, Mr. Radheyshyam, Sri P. Jena, Sri R.C. Behera and at the end he alsowishes to express his sincere thanks to his parents, wife and family members who gave their totalsupport.

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TABLE OF CONTENTS

1. INTRODUCTION1.1 Fish as food

1.2 High multiplication capacity and minimal water requirement1.3 Low energy requirement for protein production1.4 Warm water favours fish growth1.5 Aquaculture production potential1.6 Employment potential2. PRINCIPLES OF FRESHWATER FISH CULTURE2.1 Pond ecosystem2.2 Oxygen budget2.3 Desirable fish species for culture2.4 Living space2.5 Supplementary feeding2.6 Pond fertility2.7 Diseases and their control3. CHARACTERISTICS OF UNDRAINABLE AND DRAINABLE PONDS3.1 Undrainable ponds 3.1.1 General morphometry 3.1.2 Physico-chemical environment 3.1.3 Community structure and function3.2 Drainable ponds4. PRESENT PRACTICES OF FISH CULTURE IN PONDS4.1 Carp culture4.2 Integrated carp farming 4.2.1 Integrated fish-pig farming 4.2.2 Integrated fish-duck farming 4.2.3 Integrated fish-poultry farming4.3 Air-breathing fish culture4.4 Sewage-fed fish culture5. RENOVATION OF EXISTING PONDS5.1 When to take up the renovation work5.2 Deweeding5.3 Dewatering and drying5.4 Contouring5.5 Desilting5.6 Reclamation of derelict water bodies5.7 Maintenance of dykes6. CONSTRUCTION OF NEW PONDS AND FARMS6.1 Site selection 6.1.1 Topography 6.1.2 Source of water and its quality 6.1.3 Soil type6.2 Designing 6.2.1 Water area ratio among pond types 6.2.2 Dyke6.3 Construction 6.3.1 Time of construction 6.3.2 Preparation of site 6.3.3 Marking the outlines

6.3.4 Pre-excavation work 6.3.5 Pond excavation and construction of dykes 6.3.6 Water inlet structure6.4 Maintenance7. FISH SPECIES SUITABLE FOR CULTURE IN PONDS7.1 Criteria for selection of suitable fish species7.2 Fish species suitable for culture in undrainable ponds 7.2.1 Catla 7.2.2 Rohu 7.2.3 Mrigal 7.2.4 Silver carp 7.2.5 Grass carp 7.2.6 Common carp8. PROCUREMENT OF INPUTS8.1 Procurement of seed 8.1.1 Collection of spawn from riverine sources 8.1.2 Bundh breeding 8.1.3 Induced spawning by hypophysation 8.1.4 Production of common carp seed8.2 Feed 8.2.1 Natural food 8.2.2 Supplementary feed8.3 Fertilizers 8.3.1 Organic manures 8.3.2 Inorganic fertilizers9. POND MANAGEMENT9.1 Pre-stocking management 9.1.1 Eradication and control of aquatic weeds and algae 9.1.2 Eradication of unwanted fish 9.1.3 Eradication of predatory insects 9.1.4 Fertilization of ponds9.2 Stocking 9.2.1 Stocking of nursery ponds 9.2.2 Stocking of rearing ponds 9.2.3 Stocking of growout/stocking ponds 9.2.4 Method of stocking9.3 Post-stocking management 9.3.1 Feeding 9.3.2 Periodic fertilization 9.3.3 Pond environmental monitoring 9.3.4 Fish health monitoring10. MANAGEMENT OF COMMON HAZARDS10.1 Deficiency of dissolved oxygen10.2 Appearance of algal blooms10.3 Common carp problem10.4 Problem of no rain and plenty of rain10.5 Problem of predation

10.6 Poaching10.7 Leakages in embankment10.8 Outbreak of diseases 10.8.1 General considerations 10.8.2 Common diseases 10.8.3 Therapy of fish diseases11. HARVESTING11.1 Harvesting in nursery ponds11.2 Harvesting in rearing ponds11.3 Harvesting in growout ponds 11.3.1 Complete harvesting 11.3.2 Partial harvesting11.4 Application of proper gear11.5 Precautions12. TRANSPORT AND MARKETING12.1 Transport of fresh fish12.2 Transport of live fish 12.2.1 Conditioning and preparation for transport 12.2.2 Open system of transport 12.2.3 Closed system of transport 12.2.4 Drugs and chemical aids12.3 Marketing 12.3.1 Market potential 12.3.2 Marketing of table-size fish 12.3.3 Marketing of fish seed13. ECONOMICS OF CULTURE OPERATIONS13.1 Raising of fry13.2 Raising of fingerlings13.3 Raising of table-size fish14. AQUACULTURE EXTENSION14.1 Objective14.2 Launching aquaculture extension programme 14.2.1 Programme planning 14.2.2 Programme implementation 14.2.3 Programme evaluation14.3 Important considerations15. REFERENCESAPPENDICES



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1. INTRODUCTIONFish culture is the rational cultivation of fish in a confined water area where the practices of bothagriculture and animal husbandry are applicable. The soil and water management aspect of fish culturepractice involving application of organic manures and inorganic fertilizers for the production ofmicroscopic plants, the phytoplankton, is basically similar to agriculture while husbandry of fish such asfeeding, breeding and health care is more or less similar to a livestock farming system. This farmingsystem is also unique in that the farmed animal is cold-blooded or poikilothermic and lives in a watermedium. Although this fish farming is approximately 2 000 years old, the importance of it has beenrealized only recently in the face of mounting pressure on land resources and scarcity of animal proteinfor the ever increasing human population. While introducing fish culture, it seems reasonable to discusscertain important aspects of fish farming systems and their relevance to the rural developmentprogramme of developing countries.

1.1 Fish as Food

Malnutrition and starvation are the two serious problems being faced by millions of rural poor in most ofthe developing countries. The problem of malnutrition is in fact more serious and of a bigger dimensionthan the starvation problem and is caused mainly due to animal protein-deficient diets. Animal protein isessential for proper growth, repair and maintenance of body organs and tissues. Fish contain about 16–20% protein compared to about 12% in egg, 3.5% in milk and 6–8% in rice and wheat. Moreover, it iswholesome, tasty, highly nutritive and an excellent source of essential minerals, vitamins and essentialamino acids. At present about 31% of the total animal protein supply in the Asian region is in the form offish protein. For the poorest segments of the population, fish is not only the most important animal proteinsource, but often the only one.

1.2 High Multiplication Capacity and Minimal Water Requirement

The reproductive potential of fish compared to any other farmed animal is also very high. A kilogram offemale cultivable carp species yields on an average about 0.1 million eggs, each of which has thepotential to become 1 kg fish in about a year. No livestock animal possesses this magnitude of fecundity.Although fish needs water as a medium to survive and grow, it consumes minimal quantity of watercompared with any livestock or agricultural crop. Fish also enriches the water with its voided metabolitesthus making the water more productive for agriculture.

1.3 Low Energy Requirement for Protein Production

Fish culture systems require a relatively less amount of energy for protein production than any otherfarming system. Carp culture, depending upon culture practices, requires energy at the rate of 22–468KJ/g of protein production while a land animal farming system needs over 550 to 3 400 KJ/g.

1.4 Warm Water favours Fish Growth

Fish are cold blooded or poikilothermic animals. In other words they cannot maintain a constant and highbody temperature like other livestock animals. Instead, their body temperature fluctuates according to thesurrounding temperature. In warmer climates, their metabolism accelerates and they grow faster, while incolder climates, the metabolic rate slows down, resulting in a reduced rate of growth. In this way they

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save energy by not spending it for maintaining a higher and constant body temperature.

1.5 Aquaculture Production Potential

Although the world's total marine production now stands at more than 80 million tons per year, all trendsindicate that a saturation point is quickly approaching. During the past decade the growth rate hoveredaround 2%, much lower than earlier decades.

On the other hand, tremendous potential exists in aquaculture. Aquaculture presently produces over 8million tonnes of fish and shellfish annually. It is estimated that Asian aquaculture production could beraised to 20–30 million tonnes a year by the end of the century. Aquaculture production has increased atan annual growth rate of nearly 7% between 1975–84.

1.6 Employment Potential

Aquaculture is also considered to be a potential source of employment for poor farmers and displacedcapture fishermen. Rapid development of aquaculture has already generated considerable employmentthrough culture of marketable fish, fish seed production, and marketing of fish and fish seed. TheNational Agriculture Commission of India while estimating the employment potential of fish culture hasindicated that every tonne of fish produced provides employment to 2.5 persons.

The other important advantages of fish farming are that the production is carried out within easy reach ofconsumers and also the harvesting can be adjusted to demand, thus minimising distribution problemsand spoilage.

Rural ponds in Asia, hitherto producing at subsistence level, have succeeded in increasing production perunit area through improved culture practices involving higher stocking densities, polyculturecombinations, pond manuring and feeding. The switch over from monoculture practice to polyculture hassignificantly contributed toward higher production and the prospect of polyculture appears very bright asthe fish seed of desired species is becoming easily available due to the establishment of a large numberof hatcheries. During recent years, advances have also been made in traditional aquaculture systemspractised in rural India by the development of composite fish culture, a system of polyculture of a group ofcomplementary and supplementary freshwater species of fast growing carps in undrainable ponds. Withthe successful demonstration in different agroclimatic zones of India, gradual improvements in technologyhave been made and it is now possible to obtain a production rate of over 10 t/ha/yr in experimentalponds and up to about 5 t/ha/yr in farmers' ponds against the traditional average rate of production of 600kg/ha/yr. To meet the increasing demand of seed of culturable carps, hypophysation techniques havealso been developed for both Indian and Chinese carps and as a result they are now being bred incaptivity even by fish farmers in remote villages. The emergence of this culture technology suitable forundrainable ponds and the simultaneous development of hypophysation techniques for fish seedproduction has completely revolutionized fish farm productivity.

This manual intends to provide the basic concept and practical guidelines of fish culture in undrainableponds. Since it is prepared especially for extension agents and field workers, certain important thingshave been repeated and at times experimental results have been simplified with a view to making it morepractical, simple and illustrative. It outlines the practices of procurement and propagation of fish seed,rearing of spawn to fry and fingerling stage, and production of table-size fish following simple sequentialsteps. Like other farming systems this culture system is also prone to certain unexpected hazards forwhich one has to be prepared and properly equipped. Such hazards are disease outbreaks, oxygendepletion, pollution, flood, drought, poaching, etc. The content of this manual is a synthesis of theauthor's personal field experience, the information gathered from published literature, and theobservations of other workers in India. Based upon Indian experience, water resources in otherdeveloping countries with similar agroclimatic conditions may be utilized for the development of fishculture. It is hoped that this manual will serve as a practical guide to extension workers in popularizingfreshwater fish culture in undrainable ponds.



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2. PRINCIPLES OF FRESHWATER FISH CULTUREAn understanding of the following basic principles of freshwater pond fish culture is essential.

2.1 Pond ecosystem

Like agriculture, fish culture is also based on a series of processes involving reception and transformationof solar energy. In the pond ecosystem solar energy is utilized for primary production by chlorophyll-bearing plants such as planktonic algae and macrophytes. This conversion of solar energy into chemicalenergy (food) is guided by the photosynthetic and chemosynthetic activities going on in the aquatic plantcommunity and the rate at which this is carried out is called primary productivity of that ecosystem.

A part of the primary production is cycled through different trophic levels resulting in fish production. Herecomes the community of consumers that comprise microscopic as well as large animals, which areunable to synthesize their own food and feed upon primary producers. Different forms of pond life arelinked together through predator-prey relationship (Fig.1). This chain of food production, which follows ageneral pattern, primary producers - herbivores-carnivores - appears too simple and straight. But, in fact,it is a complex food web with various cross linkages.

Fish populations may be classified into several trophic levels, depending upon their position in this foodchain. Phytophagous fish such as grass carp and silver carp belong to the second trophic level as theyfeed upon the first trophic level organisms. Likewise, zooplankton, feeding upon phytoplankton, alsobelong to the same category. Carnivorous fish communities thriving upon zooplankton or herbivorousfishes occupy the third trophic level while other predatory fishes preying upon carnivorous fishes belongto the fourth trophic level (Fig. 2). A relatively simple food chain operates in fish ponds, but a complexone occurs in lakes and other larger aquatic ecosystems. The picture becomes even more complicated inlarge water bodies such as rivers and seas where complex food chains are referred to as food webswhich in fact represent several interconnected food chains. There are some fishes which occupy mixedpositions, between different trophic levels. They consume both plants and animals and as such, cannotbe naturally categorised into any one particular trophic level.

A properly managed pond presents an example of a simple food chain under simple conditions. Here thenumber of food chains is reduced by encouraging the growth of phytoplankton. The macrophytes such asrooted green plants, floating plants, etc., are not allowed to grow. Phytoplankton is consumed by thezooplankton in the water column, whereas its detritus is utilized by benthic invertebrates. Phytoplankton,zooplankton, detritus and benthic organisms serve as food for the stocked fishes such as the desiredcarp species. Thus, as much of the available solar energy as possible is utilized for fish production byproper pond management.

Primary productivity is dependent on light, carbon dioxide, temperature and essential nutrients, each ofwhich can be a limiting factor. Of these factors affecting primary production in ponds, the one that can bemanipulated easily is the quantity of nutrient elements through the application of nitrogenous, phosphaticand potassic fertilizers, as in agriculture. In ponds, only the top 2 to 5 cm of soil is concerned withnutriention exchange, and the soil below plays a negligible role in the production cycle. Undrainableponds receive dissolved nutrients and sedimentary particles carried by rain water from the catchmentarea. Besides, production and decomposition of minute plant and animal organisms in ponds also modifythe properties of the pond bottom to a great extent. The nature and quantity of fertilizers determines thespecies composition to be used in a culture system. At low phosphate concentration, diatoms are

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common, but with increasing concentrations green algae become more frequent, eventually giving way toblue-green algae. In addition, excessive phosphate gives rise to phytoplankton blooms which check thelight penetration and thus lower the pond productivity through ‘autoshading’ (Prowse, 1968).

Figure 1. Pond Ecosystem

Figure 2. Food Pyramid

Light energy is one of the major inputs in primary production and hence the success of fish culturedepends largely on the efficient utilization of incident light. When incident light strikes the water surface, itis partially reflected and partially transmitted into the water where part of it is utilized in the process ofphotosynthesis and the rest is scattered or absorbed by suspended particles. In turbid waters, more lightis scattered or absorbed, thus allowing the light penetration only to shallow depths. The rapiddisappearance of light in such waters affects adversely the growth of diatoms. The bottom layer of water,being devoid of photosynthetic plants and also being in close contact with the decaying organic matter,suffers from oxygen depletion causing critical stress conditions for the fish. Thus, it is important thatprimary producers must provide oxygen to support the total biological respiration during darkness andalso during the less favourable (warmer, overcast or rainy) days apart from providing food for the secondand third trophic-level fish.

Table 1Solubility of oxygen under different temperatures

at 760 mm of Hg pressure(Adapted from APHA, AWWA, WPCF, 1980)

Temperature(°C)

Solubility ofoxygen (mg/l)

Temperature(°C)

Solubility ofoxygen (mg/l)

15 9.76 26 7.9916 9.56 27 7.8617 9.37 28 7.7518 9.18 29 7.6419 9.01 30 7.5320 8.84 31 7.4221 8.68 32 7.3222 8.53 33 7.2223 8.38 34 7.1324 8.25 35 7.0425 8.11

2.2 Oxygen budget

The concentration of dissolved oxygen in the water, which depends on the temperature, is an essentialcomponent of the aquatic environment to govern the carrying capacity of a pond. Variations inconcentration of dissolved oxygen may occur due to the following three important factors:

the saturation level of oxygen in water decreases as the temperature rises;

supersaturation is an unstable state, and

plants not only photosynthesize to produce oxygen, they also respire and consume oxygen.

The saturation value for dissolved oxygen available for fish life at 20°C water temperature is more thanthat at 30°C at a particular atmospheric pressure (Table 1). Dissolved oxygen (Do) concentration isalways high at lower temperatures and gradually decreases with increase in temperature. In naturalwaters, including undrainable fish ponds, DO values are constantly changing because of biological,physical, and chemical processes (Fig. 3). The air above the pond water surface may be considered tohave a more or less constant percentage of oxygen. However, the partial pressure of oxygen in the airmay vary slightly at a given location because of differences in atmospheric pressure. Transfer of oxygenfrom air to water will occur when water is undersaturated with DO, and oxygen will diffuse from water toair when water is supersaturated with oxygen. However, the diffusion of oxygen into the pond water isvery slow, except under conditions of strong turbulence, hence the most important source of oxygen isthat generated during photosynthesis. As discussed earlier, light is the most essential source inphotosynthesis where penetration into the water column is regulated to a large extent by suspended orcolloidal particles (turbidity) and also by dense plankton levels. Sometimes, phytoplankton blooms or algalscums limit light penetration causing reduction in photosynthetic rates, even in waters with adequatenutrient concentrations. Oxygen production by phytoplankton is greatest near the surface and decreaseswith the increase in depth because of self-shading. When heavy infestation of aquatic weeds and densebloom of plankton occur, the situation becomes much more complex. On the other hand, these areadditional sources of oxygen at daytime; but on the other hand, they also respire and consume oxygenthroughout day and night. At times the pondwater is supersaturated with oxygen during the day, which isa highly unstable state, while during the night, a greater proportion of oxygen is used up for theirrespiration, thereby reducing the availability of oxygen to fish. Thus, it creates a wide fluctuation in thelevel of dissolved oxygen, adversely affecting fish life. Figure 5 shows a situation created by algal bloomor weed infestation where wide variations between actual and expected oxygen production do occur(Figs. 4 and 5). In fact, under such situations oxygen production increases to its maximum during thedaytime leaving surplus for the fish even after consuming for their own respiration, but at night thissurplus level drops down to critical level. Under conditions of heavy algal blooms and weed infestation,the phytoplankton and aquatic weeds actually consume more available oxygen during day and night thanthey produce during the whole day (Fig. 6). During cloudy days, when the incident light is inadequate forphytosynthesis, the situation in terms of availability of DO becomes worse.

Aerobic decomposition of organic matter by bacteria is also an important drain on the oxygen supply inponds. Aerobic decomposition requires a continuous supply of oxygen and proceeds more rapidly whenDO concentrations are near saturation. However, decomposition also occurs under anaerobic conditions,but the rate of degradation of organic matter is not as rapid and complete as under aerobic conditions.Under aerobic condition, the end product of decomposition is primarily carbon dioxide. At times high rateof bacterial decomposition of dead organisms and other organic bottom deposits lead to a conditionfavouring the increase of the level of carbon dioxide and other abnoxious gases, with a simultaneousdepletion of DO, resulting in fish kills and planktonic collapses (Radheyshyam et al., 1986). Therefore, itis important that the pond water should provide adequate oxygen to support the total biologicalrespiration during the hours of darkness.

Figure 3. Oxygen Cycle in Pond

Figure 4. Effect of Algal Bloom on Oxygen Production

Figure 5. Dial Oxygen Production/Consumption Pattern under Algal Bloom/Weed Infestation

Figure 6. Relation between Stocking Density and Production

2.3 Desirable fish species for culture

The choice of fish species is very important in maximizing production, both in terms of quantity andquality.

Since considerable amount of energy is lost in successive trophic levels of the food chain, efficient fishculture always aims at making the chain as short as possible. Because of this, herbivorous fishes arealways preferred to carnivorous fishes, the latter being mostly excluded because of their longer foodchains. Mixed species farming or polyculture yields a higher production than single species farming. It isobvious that any single species cannot utilize all the available food in a pond because of its specificfeeding habit and hence a combination of compatible species with complementary feeding habits areusually stocked to make better use of the natural food available in the pond. Selection of the speciesshould be based on the productivity of a pond, availability of artificial food resources, availability of seedand the marketing prospects. The principal considerations in species combination are that they havecomplementary feeding habits, they occupy different ecological niches, they attain marketable size atmore or less the same time, they tolerate each other, and they be non-predatory in nature. A combinationof plankton and macrophyte feeders is most usual. Ungrazed phytoplankton is fed upon by zooplanktonand to utilize them, the zooplankton feeders are included in the combination. The combination of thephytoplankton-feeding silver carp (Hypophthalmichthys molitrix), the zooplankton-feeding bighead carp(Aristichthys nobilis) and the weed-eating grass carp (Ctenopharyngodon idella) is well known in Chinaand Southeast Asia. In India, under composite fish culture, six species of fish viz. catla (Catla catla), rohu(Labeo rohita) and mrigal (Cirrhinus mrigala) along with three Chinese carps such as grass carp, silvercarp and common carp (Cyprinus carpio) are stocked together so as to utilize most of the fish foodorganisms present in the pond (Lakshmanan et al., 1971; Sinha et al., 1973; Chaudhuri et al., 1976).Other similar combinations may work just as well, but the most important aspect is to try to establish abalance between the species based on the food spectrum of the pond (Sinha, 1971).

Stocking density: Normally fish production increases with the increase in the number of fish stockedper unit area upto a level and then starts decreasing (Fig. 6). Higher stocking density results in increasedtotal production, as there is better utilization of the available food, but in such cases the individual weightand size is reduced. On the other hand, lower stocking density yields larger individual fish. Properstocking rate for a pond is that optimum level which results in a given time, usually a year, in a productionwhich is highest in quantity and quality of fish, and most profitable. In ponds where no artificial feed isused, the total crop becomes dependent on the primary production and in such cases simply byincreasing the stocking density, the increase in the total production is not possible. Even withsupplementary feeding the scope of increasing stocking density and fish yield is limited; it increases to anoptimum level and then starts decreasing.

Under crowded conditions fish compete for food and space and are stressed due to aggressiveinteraction. Fish under stress exhibit decreased feed consumption and slow growth and are predisposedto many parasitic and microbial infections. Increase in stocking density simultaneously increases the totaloxygen demand with obvious dangers. In undrainable ponds, accumulation of excretory products of thefish population also suppresses their growth rate. With efficient removal of such metabolites by aeratingthe pond water, the stocking rate can be increased further, thereby enhancing production.

2.4 Living space

It has been observed that under identical conditions of management levels and stocking density fish growbigger in larger ponds. In Malaysia, grass carp, Puntius sp. and monosex Tilapia mossambica grewbigger in ponds of a larger area indicating the living space phenomenon (Chen and Prowse, 1966). Inother words, the rate of production in a 0.2 ha pond will be more than double that of a 0.1 ha pond,despite the fact that the stocking rate per unit area is the same and all other management componentsincluding the genotype of the stocking materials and ecological conditions remain the same. The pondshaving larger surface area are subjected more often to wind action resulting in greater rate of diffusion ofatmospheric oxygen into the water. Larger ponds have other advantages also, viz. better cooling actionby wind. In smaller ponds, water tends to stagnate and in hot weather tends to heat up quickly.

Though it is preferable to have ponds of a large size, there is a physical limitation. Large ponds aredifficult to fill and even more difficult to harvest. There must be an optimum size and shape of the pond tobalance size with practicability of management, i.e. large enough to allow proper growth of fish, but at thesame time small enough to be manageable. Recommended optimum size is 0.4 ha – 1.0 ha (Sinha andRamachandran, 1985).

2.5 Supplementary feeding

With the increase in carrying capacity of the pond either by aeration or circulation of water, fish growthcan be increased further by supplementing the natural food with some artificial feed. This is the singlemost important management component for increasing production. In intensive and semi-intensiveculture of fishes, supplementary feeding is indispensable. The quantity of feed and the form in which it isoffered affect the rate of consumption. Temperature, dissolved oxygen level, crowding and healthcondition, etc., affect the rate of food consumption.

2.6 Pond fertility

Organic matter and mineral constituents of the pond soil supply the required nutrients for chemical andbiochemical production processes. The pond bottom also provides a suitable environment for thedecomposers like bacteria and fungi to mineralise organic components of the pond sediment and releasesoluble nutrients. Sometimes such nutrients are not available in sufficient quantity in the pond and hencethey are added from outside in the form of fertilizers. Since plankton production is often limited byinadequate quantity of phosphorus which is essential for the assimilation of nitrogen into cellular matter,phosphatic fertilizers are widely used in fish culture.

Unlike phosphorus, availability of nitrogen does not depend on the inherent status of soil, since it isbrought to the soil by different processes. Nitrogen fixation by azotobacteria, blue-green algae,atmospheric electric discharges and photochemical fixation are some of the potential sources of pond

nitrogen. In a tropical climate, the fixation of atmospheric nitrogen by blue-green algae is of considerableimportance. However, when nitrogen is added from outside, its form, viz., ammoniacal or nitrate is alsovery important. It is advisable to use the ammoniacal form of nitrogen in acid and neutral soils and thenitrate form in alkaline soil (Saha, 1969). Though there is a considerable loss of nitrogen from theammoniacal form in alkaline soil, the use of ammonium sulphate in low doses is usually recommended,keeping in view the role of sulphate in reducing the soil alkalinity.

Potassium is the other essential nutrient for plant growth. In ponds it is easily available both in soil andwater and does not form insoluble salts and is rarely deficient except in acid peaty soil. Yet, a littlepotassium when added to the pond, stimulates the production of plankton.

Organic matter of the pond sediment is also an essential factor regulating the bacterial activity. In thiscontext, the ratio of organic carbon to total nitrogen (C/N ratio) is important. Periodic application oforganic manures ensures to a certain extent replenishment of nutrients and also provides an energy basefor bacterial activities. Apart from this, the organic matter and the bacterial flora are also directlyconsumed by zooplankton and some fish species.

2.7 Diseases and their control

Various intensification approaches such as increased stocking rates, increased feeding, fertilizationprogrammes, etc., sometimes result in nutrient accumulation, frequent appearance of algal blooms,dissolved oxygen deficiency and other water quality problems in undrainable ponds. As a result of suchwater quality and environmental problems, the infectious diseases and their control assume importance.A fish farming system is unique in that the farmed animal is poikilothermic and lives in water whererespiratory oxygen level compared to air is limited and becomes critical at times. Further, metabolic wasteproducts, left-out feed materials and organic load of the pond bottom can affect certain exposed vitalorgans and tissues of fish. All such factors affect fish health and contribute to the risk of diseaseoutbreaks.

The above basic facts need careful consideration while planning for freshwater pond fish culture. Thehabitat of an undrainable pond is very varied and dynamic, but can be monitored and managed forincreasing fish production.



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3. CHARACTERISTICS OF UNDRAINABLE AND DRAINABLEPONDS

In India ponds are relatively small and shallow bodies of impounded water with limited wind action. Theymay be called perennial if they retain water the year round or temporary/seasonal, if they do soseasonally. They may be further classified as drainable ponds and undrainable ponds, depending uponthe drainage facility by gravity. Drainability imparts a very desirable feature to a pond and some authorsprefer to call only the drainable type of ponds as fish ponds. However, Indian experience has shown thatexperimental fish production to the tune of over 10 tonnes/ha/yr can be achieved even from suchundrainable ponds through a proper understanding of the biotic and abiotic components of the ecosystemand adoption of suitable culture technologies. Hence, before adopting any culture technology, it isimperative to have an idea about the basic biology of the pond types in terms of environmental factors,community structure and community metabolism.

3.1 Undrainable ponds

The periods of ‘plenty rain’ and ‘no rain’ usually prevail in regions having undrainable ponds. With theonset of monsoon, torrential downpours sweep across the land and the amount and frequency of raindecrease towards the end of the monsoon. Severe floods may occur, whereas a late monsoon or earlymonsoon of short duration may result in serious drought. Both flood/ rain and drought influence theecosystem of the ponds on such lands. Small, shallow and seasonal ponds get filled or dry, whereasdeeper perennial ponds exhibit considerable fluctuations in water levels accordingly. Though these pondsare basically constructed for storing water in such areas for multiple uses, ranging from supplying drinkingwater for human population, live stock, etc., to supplying water for agriculture, recent trend is to utilizethem for fish culture. The description of the undrainable ponds is based upon the studies conducted at theCentral Institute of Freshwater Aquaculture, Dhauli, Bhubaneswar, India, under an extensiveenvironmental monitoring programme of rural undrainable ponds.

3.1.1 General morphometry

Undrainable ponds in general are relatively small, perennial or seasonal water bodies constructed orexcavated for multiple uses. Some of these ponds have proper embankments. They greatly vary in theirdimensions ranging from 0.02 ha to over 2.5 ha in water surface area and 50 cm to 250 cm in depth.Larger ponds are relatively deeper while smaller and seasonal ponds are shallower. Unlike shallowseasonal ponds, the bottom of the perennial ponds is never exposed to sunlight and therefore the wholeecosystem of such ponds is quite different from those of shallow and seasonal ponds. Use of theseponds by villagers for multipurpose provides the source of organic enrichment. Usually the only source ofwater for these undrainable ponds is the heavy rainfall during the monsoons. However, in some cases,the pond bottom is cut below the water table so that ground water enters the ponds. As soon as themonsoon ceases, the water level starts decreasing gradually and shortage of water is quite commonduring the pre-monsoon season. Water is lost from the pond through evaporation, seepage andtranspiration by aquatic macrophytes and the trees and shrubs planted along the pond sides.Macrophytes tend to appear in both perennial and seasonal types of ponds but with increased intensity inshallower ponds.

Presence of thick sediment layers in the bottom is the most characteristic feature of these ponds whichgradually get accumulated during the course of time and vary between a few centimeters to over a meter

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and half in thickness. The quality and quantity of sediment deposition depend mainly upon the originalsoil, method of construction, nature of embankments, macrophyte cover, pond productivity, organic andinorganic additions, species cultured, etc. Although sedimentation is relatively faster in smaller ponds,there is a positive correlation between the age of a pond and its sediment thickness.

3.1.2 Physico-chemical environment

The water depth and total volume of water available for individual fish are crucial in fish culture systems.Adequate water depth is needed not only for optimum growth, but also to provide enough space andoxygen for fish life. Water levels in these ponds are mainly dependent upon monsoon rains. After themonsoon season, the water level starts decreasing gradually and shortage of water is quite commonduring the summer season which is the most crucial time for fish culture since the fish growth rate isfaster in this period. In fact, during the time of lowest water level the ponds contain the maximumbiomass. In shallow and seasonal ponds, sufficient phytoplankton population fails to appear and the softsediment layer is vigorously stirred up by fish, making the water more turbid, thereby reducing thephotosynthetic process by limiting light penetration. Eventually, the total amount of available dissolvedoxygen may not be, at times, sufficient to meet the demand for total community respiration and thechemical oxygen demand of the sediment, resulting sometimes in mass fish kill and planktonic collapse(Radheyshyam et al., 1986). On the other hand, in deeper perennial ponds where the water column ismore than 3 m, fish life is again adversely affected. In such ponds the photosynthetic or oxygenproducing zone is less in comparison with the oxygen consuming layer.

In addition, the sediment proper and the sediment community also consume a considerable amount ofoxygen. All such conditions lead to a negative oxygen balance.

The water in most of these ponds remains slightly alkaline (pH 7.0–9.0). The NH4-N (ammonia-nitrogen)content of the waters remain below 0.02 mg/l with even lesser quantities of No3-N (nitrate-nitrogen). ThePo4-P (phosphate) concentrations remain low and these chemical features of such ponds suggest thatthese waters are highly nutrient-deficient, particularly in nitrogen.

On the contrary, the pond sediment is rich in organic and inorganic nutrients. The organic carbon rangesbetween 3 (in newly excavated ponds) and 50 mg/g dry sediment weight (in older ponds). The nutrientstatus of the sediment differs completely from that found in the overlaying water column (Olah, 1983). Ingeneral, all the basic nutrients in the pond sediment are about thousand times higher than in theirrespective water column.

Carbon dioxide and oxygen are the most important gases affecting the pond community including fish.During the photosynthetic activity, carbon dioxide is usually at zero level while during the darker period itsconcentration increases. At higher concentrations it may be toxic to fish life. Carbon dioxide toxicityincreases with decreasing level of dissolved oxygen. Carbon dioxide concentration can be tolerated upto20–30 ppm in these ponds provided oxygen is near saturation.

3.1.3 Community structure and function

Bacterioplankton and phytoplankton constitute the basic food for the fine filter feeder fish species andalso for the zooplankton which form the main food of the rough filter-feeder species. The bacterioplanktonpopulation is always higher in those ponds which are associated with the activities of larger human andlivestock populations. Most of the relatively older ponds with frequent appearance of Microcystis bloomhave higher levels of bacterioplankton population (3–10 million/ml). On the contrary, the newlyconstructed and recently desilted ponds have less dense bacterioplanktonic community, around 1–2million/ml. Macrophytic infestation also significantly limits the bacterioplankton production.

The planktonic detritus originates mainly from decomposing fragments of the phytoplankton andzooplankton and has generally a concentration range of 2 000 – 20 000 number/l. The main groups ofphytoplanktonic population are Myxophyceae, Chlorophyceae, Euglenophyceae and Bacillariophyceae;whereas copepods, cladocerans and rotifers constitute the majority of zooplanktonic population. Some ofthe very old ponds having excessively thick sediment layer face Microcystis blooming. In such ponds thebenthic animal fauna is represented by a very small number. In the majority of the ponds the benthic

animal communities are dominated by red chironomids and oligochaetes indicating the general oxygendeficiency in the sediment layer.

The bacterial decomposition and nutrient recycling in ponds are greatly influenced by the anaerobicnature of the sediment. At the initial stage of Microcystis bloom in older ponds, the oxygen production hasbeen found to be the highest (1) (over 15 g O2/m2), whereas the total community respiration remains

considerably low (2) (below 10 g O2/m2). However, during the active decomposition stage of Microcystis

(plantonic collapse stage) the total oxygen production level goes lower (3) (5–6 g O2/m2) than that of the

community oxygen consumption (4) (6–7 g O2/m2). In older ponds, especially those having thickanaerobic sediment, the biochemical oxygen demand ranged between 70% and 90% of the total oxygenproduction, ultimately causing anoxic condition leading to fish kills.

The majority of rural undrainable ponds are characterized by anaerobic benthic sediments. The dead anddecaying organic matter settles down to the pond bottom (sedimentation) where it is subjected to furtherdecomposition and mineralisation. The upper layer of the sediment remains aerobic while the deeperlayers are deficient in oxygen and thus anaerobic. Some of the distinguishing features of drainable andundrainable ponds are summarised in Table 3.

These perennial undrainable ponds in tropical monsoon lands with yearround warm water under plenty oflight offer an excellent possibility for fish culture. Most of the species cultured greatly depend uponnatural fish food resources and with a limited dependence upon artificial supplementary feed. However,without proper environmental management, the water remains infertile due to the overall nutrientdeficiency with a very pronounced nitrogen limitation, although they possess a very high productionpotential. On the contrary, the pond sediments have extremely high level of organic nutrients in almostlocked-up conditions which remain unutilized due to the anaerobic nature of the pond bottom (Fig. 7).However, though regular raking up of the pond sediment, either by manual or biological means, theorganic nutrients could be released for making the pond water more productive.

Proper management methods can optimise fish production in perennial ponds at most economical rateswhile seasonal ponds can suitably be utilized for fish seed rearing and also for short-term fish productiondepending upon the duration of water retention. The general feature of the properly managed and ill-managed undrainable fish ponds are shown in Figures 8a and 8b.

3.2 Drainable ponds

Ponds which can be supplied with water and drained of its water according to the requirements of the fishfarming operation are known as drainable ponds. These ponds require suitable ground with properembankments, inlet and outlet structures and adequate supply of water on regular basis. Studiesconducted on the filling up of ponds from various sources of water supply showed the following costfigures (Table 2).

Figure 7. Microbial Decomposition Process at the Sediment - Water Interface

Figure 8a. Well Managed Pond

Figure 8b. Badly Managed Pond

Table 3Chemical, biological and functional characteristics of

undrainable and drainable rural fish pondsin Orissa province of India

(Olah, 1983; Radheyshyam, pers.comm.)

Parameters Undrainable ponds(natural condition)

Drainable ponds(cowdung treated)

Water pH 7.0 – 9.0 7.7 – 8.2Total alkalinity (mg/l) 50 – 250 88 – 200Ammonia-nitrogen (mg/l) .005 – 0.300 .005 – 0.25Nitrate nitrogen (mg/l) .005 – 0.020 .005 – 0.20Phosphorus (PO4-P) (mg/l) 0.001 – 0.050 0.040 – 0.160PlanktonPhytoplankton (number/l) 59 – 3 911 3 – 860Zooplankton (number/l) 124 – 2 770 11 – 209Bacterioplankton (million/ml) 1.2 – 12.9 1.385 – 2.312

Benthos (number/m2.) 0 – 2 660 1 415 – 19 099

Decomposition rate ofEichornia leaves:Surface (% dry wt. loss/day) 2.88 – 3.86 2.37 – 2.86Bottom (% dry wt. loss/day) 4.02 – 10.99 1.54 – 2.84

Gross production (g carbon/m2/day) 1.76 – 10.99 1.85 – 8.11

Net production (g carbon/m2/day) (-)1.29 – 1.35 (-)2.4 – 1.875

Community respiration (g carbon/m2/day) 1.66 – 11.34 2.261 – 6.071

Sediment oxygen consumption 4.887 – 7.943 0.1766 – 3.514

(g oxygen/m2/day)



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4. PRESENT PRACTICES OF FISH CULTURE IN PONDS

4.1 Carp culture

The most successful system of pond fish culture is the polyculture of three Indian major carp species -catla, rohu and mrigal along with three Chinese carps viz. silver carp, grass carp and common carp. InIndia this is commonly known as composite fish culture. The best results in terms of fish production in thissystem results not only through a judicious combination of species, but also due to appropriatemanagement techniques including pond fertilization, supplementary feeding and health care. On thebasis of growth performance of different species, modifications are often made in stocking density,species ratio, fertilization schedule and supplementary feeding programme in different agroclimaticconditions. High rates of fish production to the tune of over 5 500 kg/ha/6 months, 7 200 kg/ha/8 monthsand over 10 tonnes/ha/yr have been achieved in composite fish culture trials conducted in differentagroclimatic conditions of India.

The carp culture system as a whole is operated as a three-tier culture system where the practices areadopted for rearing fish during their different stages till they are harvested. Spawn (post larvae) arereared upto fry (2–3 cm) stage in nursery ponds, fry to fingerlings (8–12 cm) in rearing ponds and finallyfingerlings to table-size fish in composite fish culture ponds or stocking ponds. Relatively smaller,seasonal ponds are mainly used for rearing spawn to fry stage and harvested after 2–3 weeks. Severalcrops (3–4) of fry are usually taken during the season. Pond fertilization by cattle manure and feedingwith 1:1 mixture of oil cakes and rice bran is the usual practice. Fry raised in nurseries are reared uptofingerlings in slightly bigger ponds (0.05 – 0.1 ha) of seasonal or perennial in nature. Fingerlings areremoved after 3 months and stocked in composite fish culture ponds.

4.2 Integrated carp farming

An integrated approach of composite fish culture together with compatible combination(s) with poultry,duckery, pig rearing and cattle raising is now being adopted. Under this system of farming small livestockand farm yard animals, viz. pigs, poultry, ducks, etc., are integrated with composite fish culture by sitinganimal housing units on the pond embankments in such a way that the animal wastes and washings arediverted into fish ponds for recycling. The fish not only utilize spilled animal feed but also directly feed onfresh animal excreta which is partially digested and is rich in nutrients. Surplus excreta supports the richgrowth of planktonic fauna. Fertilizers and supplementary feed are not used, resulting in drastic costreduction (Sharma et al., 1979; 1979a). Production potential through integrated carp farming issummarised in Table 4.

Table 4Annual production through integrated carp livestock farming

Integration Fish production Animal production (live weight)Fish +Pig farming 6 – 7 ton/ha 4 000–5 000 kg pig meatFish +Duck farming 3 – 4 ton/ha 500 kg duck meat + 17 000–20 000 eggsFish +Poultry farming 4–5 ton/ha 60 000–70 000 eggs + 1 500– 2 000 kg meat

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The salient features of the various types of livestock/carp integrated culture systems are described below.

4.2.1 Integrated fish - pig farming

Pigstyes are constructed either on the pond embankment or near the pond to facilitate easy drainage ofwaste directly into the pond which acts as pond fertilizer and supports dense growth of natural fish foodorganisms (Figs.9A and 9B). Besides, fish also feed directly on the pig excreta. No other feed or fertilizeris applied to the pond. A pond is prepared by following the usual pond preparation techniques (Section9.1) and stocked with fingerlings of all the six species of carps cultured under composite fish culture athigher of 8 000–9 000/ha with surface, column, bottom feeders and grass carp in the ratio of 40:20:30:10.Marketable size fish are sold by partial harvesting while final harvesting is done only after 12 months offarming.

About 2 months-old weaned piglets are fattened for six months when they attain slaughter size (60–70kg) and similarly a second crop is raised within the next six months. About 30–40 pigs should be kept forproper fertilization of the pond. Pigs are fed on mash at an average rate of 1 kg/day. Green grasses oranimal fodder is also provided. Grass with interlocked soil in root system (sod) are provided once a weekto avoid mineral deficiency.

Grass carp is fed with aquatic weeds or green animal fodder.

Fish yields ranging from 6 000–7 000 kg/ha/yr are generally obtained.

4.2.2 Integrated fish - duck farming

This is also an efficient integrated system based on the principle of waste recycling. Pond preparationtechnique is basically the same. A duck house is normally constructed on the pond embankment or on thepond water on a floating platform (Figs. 10A and 10B). When given free range, ducks feed on aquaticorganisms such as insect larvae, tadpoles, molluscs, weeds, etc. The duck droppings like pig excreta actas fertilizer. Ponds are prepared and stocked with fingerlings of all the six carp species at 6 000 ha withsurface, column, bottom feeder and grass carp in the ratio of 40:20:30:10. Fingerlings of over 10 cm arepreferred for stocking. About 200–400 ducks are sufficient to adequately fertilize a l ha pond. Normally 2–3 months old ducklings are preferred. Although ducks are able to feed upon natural food from the pond,they are also provided with duck feed at the rate of 100 g/bird/day. Ducks start laying after 5–6 monthsand continue for 2 years. Fish yields ranging from 3 000–5 000 kg/ha/yr are generally obtained.

Figure 9a. Fish-cum-pig farming (wooden pigsty)

Figure 9b. Fish-cum-pig farming (concrete pigsty)

Figure 10a. Fish-cum-duck farming (duck house in pond)

Figure 10b. Fish-cum-duck farming (duck house in pond dyke)

4.2.3 Integrated fish - poultry farming

Under this system of integration the poultry birds are raised in cages under a shed normally constructedover the pond embankments or in the vicinity of the pond. The space requirement in such a system ofpoultry raising is about 1 sq.ft. per bird. The droppings of the birds fall on the floor from where these arecollected and applied to the pond. The chicken house can also be built directly over the pond water sothat the excreta may fall in the pond water underneath. Usually, 400–600 chickens/ha of pond water

surface are used. No feed or fertilizer is applied in the pond, except aquatic vegetation for the grass carp.Fish production at the rate of 4–5 t/ha is possible using this system.

In India, this system of freshwater fish culture has assumed greater significance in view of its potentialrole in recycling of organic wastes and in integrated rural development (Sinha, 1981).

4.3 Air-breathing fish culture

Besides freshwater ponds, there are many low-lying areas which become waterlogged during the rainyseason. In course of time these areas get infested with dense aquatic vegetation and turn into swamps.Swamps are also formed along the irrigation canals due to profuse seepage. These areas are best suitedfor culturing airbreathing fishes such as Koi (Anabas testudineus), Singhi (Heteropneustes fossilis),Magur (Clarias batrachus) and Murrels (Channa sp.) without getting involved in costly processes of theirreclamation essentially needed for carp culture. There are three levels of culture practices viz. low costculture, semi-intensive culture and intensive culture depending on inputs and level of management(Dehadrai, Murugesen and Pathak, 1979).

Fingerlings (6–10 g) and feed are the two material inputs used in the culture system. Fertilizer is notused. However, replenishment of water becomes an essential input in case of intensive system of culturein ponds where very high stocking rate and intensive feeding is practised to obtain very high yields(Dehadrai, Kamal and Das, 1985). Monoculture as well as polyculture of these fishes are commonlyundertaken, yielding production to the tune of 3 000 to 7 000 kg/ha/yr. Production at the rate of over 3000 kg/ha/8 months is possible through monoculture of Channa marulius in swampy ponds. In intensivesystem of monoculture of magur and singhi with frequent change of water, yields of over 15 t/ha/yr havebeen obtained. Presence of naturally occurring weeds in airbreathing fish culture ponds not only provideprotection against poachers, but also encourage the growth of insects which are consumed by the fish.The common culturable species are magur (Clarias batrachus), singhi (Heteropneustesfossilis), murrels(Channa marulius, Channa striatus and Channa punctatus) and Koi (Anabas testudineus).

4.4 Sewage-fed fish culture

The wastes, including sewage and waste water produced by the human community hold high potential forfish production. In India itself there are about 150 sewage-fed fish farms covering an area of about 12000 ha. Very high production in the order of 7–10 tonnes/ha/yr has been obtained from ponds fed withsewage which invariably contains high percentage of N,P,Ca,K,etc. An average production of about 7t/ha/yr is easily obtained using a mix culture of 5 carp species (Ghosh et al., 1985). The sewage fedponds are generally dewatered completely during summer so as to remove all the carnivorous fishes. Thepond is initially fertilized by introducing partially treated sewage effluent upto about 75–80 cm and thenclean water is pumped in to raise the pond water level to 1.5 m. Within a month the pond stabilises withrespect to dissolved oxygen and becomes suitable for stocking with fish seed. During raising ofmarketable size fish, additional fertilization with sewage effluent is carried out in small doses every monthand the pond is netted frequently to help oxygenate the water and in course of netting the marketablesize fish are also harvested.



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5. RENOVATION OF EXISTING PONDSThe majority of freshwater fish ponds in the Indian subcontinent are the dugout ponds of an undrainablenature which at times lack proper embankments. During the course of culture operations, such pondsreceive huge amounts of feed, fertilizers and manures as critical inputs, and sediment particles carrieddown by rain water from the catchment area. A portion of the organic production in the pond alsoundergoes death and decay and gradually adds to the pond bottom sediment. Thus, with theadvancement of time, a thick sediment layer is formed reducing the depth of the pond. They are quite richin organic and inorganic nutrients, but due to slow bacterial action under prevailing anaerobic conditionsthe nutrients are almost locked up in the sediment and are not available for primary production. Further,the anaerobic decomposition of the organic matter accumulated in the sediment releases harmful gasesand depletes dissolved oxygen level in the water. Thus, it becomes necessary to renovate the existingponds periodically every 4–6 years by removing sediment from the pond bottom, redressing and repairingthe dykes, etc., in order to make the ponds more suitable and to regain their fertility. For this, thefollowing practical measures are recommended.

5.1 When to take up the renovation work

As soon as the water table of the area surrounding the pond goes down the renovation work can beinitiated. Summer is the most suitable period for this Purpose as complete drying of the water body ispossible. In this period pond renovation can be carried out efficiently and economically. Removal ofslushy silt from the partially dried pond bottom is difficult, laborious and expensive.

5.2 Deweeding

It has been observed that most of the rural ponds are not properly managed and become weed-infestedin course of time. Before dewatering the pond, large floating weeds such as water hyacinth should beeradicated by pulling them out manually or mechanically. Otherwise, collection and removal of suchweeds will require more labour and time. Other rooted emergent or submerged weeds can be taken careof only after draining the pond.

5.3 Dewatering and drying

Dewatering of the existing pond is possible either by draining the water after cutting a portion of theembankment or by pumping out. If the water table in the surrounding area is high, there is considerableinflow of water from the pond bottom. This phenomenon of sub-surface secretion is called percolation. Incase the rate of percolation is high, several furrows or ditches may be made towards the lowest contourpoint where a pit may be dug out to drain all the percolated water (Fig. 11). Periodical pumping of waterfrom the pit facilitates keeping the bed dry.

5.4 Contouring

Where the bed is found to be uneven, contouring is necessary to estimate the amount of silt to beremoved. It is done by taking the level measurements at certain spots on the pond bed. It will also help inredesigning the pond taking into consideration the highest flood level and maximum rain water level.

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Figure 11. Drained-out pond with furrows

5.5 Desilting

After complete dewatering, the pond bed is allowed to dry and develop cracks in the silt mass. Thetexture of silt is different from that of the bottom hard soil and cracks quickly. At this stage dried silt is cutand removed manually or mechanically and heaped at a suitable place for its utilization in agriculturalfields. Where complete drying is not possible due to high rate of percolation, walking platforms made upof bamboos or wooden planks may be put on the slushy bed to facilitate desilting work. In some largerponds it becomes difficult to dry the central portion of the pond bottom as it is nearer to undergroundwater table. In such cases the slushy and loose silt should be scrapped and spread to the sides with thehelp of wooden planks tied with ropes for pulling. This helps in drying the silt and easy removal thereafter.

5.6 Reclamation of derelict water bodies

Derelict waters in millions of hectares, lying unutilized, are common sights in most of the South Asiancountries. Such untapped water bodies with potential for aquacultural production may be reclaimed andmade suitable for fish culture by adopting more or less similar procedures. In case of larger water areas,it would be better if they are connected temporarily to nearby natural or man-made drainage systemshaving relatively lower bed level for complete dewatering by gravity and making the entire areacompletely dry. However, if such topographic facilities are not available, heavy duty water pumps may beput into use for quicker dewatering.

In extensively large areas dewatering by draining or by pumping is not feasible. Moreover, the dry periodof the year also may not last long enough to permit the work to be completed. It has been experiencedthat such areas can also be successfully reclaimed and renovated by partitioning into smaller units byraising cross bundhs, farm roads, etc. Each newly formed unit then can be dewatered, dried and desilted.

5.7 Maintenance of dykes

In general, rural ponds lack proper embankments. During high rainfall or peak irrigation periods in canal-irrigated areas such ponds get inundated with water from the neighbouring agricultural fields causingstocked fish to escape, predators and unwanted species to enter and at times results in mass fish killsdue to pesticide pollution. Hence, provision of proper dykes is a must. Existing pond dykes should be

repaired every year after the monsoon. Rats and crabs cause great harm to pond dykes by makingholes. Such holes allow serious leakage and if not checked immediately, may endanger the stability ofthe dykes. Periodically, and especially at the time of renovation, such spots should be properly repairedby stuffing binding clay, claylime mixture or any other locally cheap cementing material. Due to poorconsolidation, erosion from the top of the dyke during heavy rains usually results in grooving out of smallchannels. These areas should be covered with earth, levelled, thoroughly rammed and grass turfed. Inrelatively larger ponds, wave action due to wind also causes large-scale dyke erosion. By putting largefloating aquatic plants such as water hyacinth along the sides of the dykes exposed to wave action duringthe windy season such erosion can be checked. Frequent erosion in steep dykes during heavy rain orwind can be avoided by strengthening the inner sides of the dykes with poles or bamboos or corrugatedcement planks.

Most of the traditional pond dykes are below the required height; as a result, overflow of water occursduring heavy rains or flood. These dykes should be properly raised and the height may be kept at aminimum of one meter above the maximum water level recorded in that area. While raising the dykes, thetop width may be kept at a minimum of 1.5 m with 2:1 slope (horizontal: vertical). Cutting the dyke toallow water into the pond from the surrounding area without any secured screening is a normal practice,which however creates many management problems. It is necessary to provide permanent inletstructures wherever is possible. Details about inlet and spillway structures are described in Section 6.

The silt mass is very rich in organic and inorganic nutrients making it most suitable for application inagriculture and horticulture. Being non-cohesive and unstable, it is unsuitable for making dykes as it maybe washed back in the pond.



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6. CONSTRUCTION OF NEW PONDS AND FARMSVillage ponds, homestead or backyard kitchen ponds, garden or farm ponds, irrigation ponds andoccasional ponds such as brick mine pits and quarries, etc., occupy enormous freshwater areas in thetropics and are used for fish culture with minor improvements. However, ponds designed and constructedfor fish culture are easier to manage and are expected to give higher production.

Although certain well-defined guidelines do exist for the construction of fish ponds, it is mainly thetopography of the site which determines the basic design of the pond/farm. There are, however, certainbasic principles to be considered when choosing a site and deciding the method of pond construction.

6.1 Site selection

Selection of suitable sites for fish farm construction is very important. The following three essentialconditions guide the proper site selection:

Topography

Source of water and its quality

Soil type

6.1.1 Topography

It is economical and convenient to construct ponds in waterlogged areas, irrigation command areas or inmarginal lands. In such areas construction cost is relatively low mainly due to limited earth cutting. Forexample, a pond of 100 m × 40 m (0.4 ha) of water area requires only 3 234 m3 of earth to constructaround a dyke of 2 m high above ground level (GL) with side slope ratio of 2:1 and top width of 1.5 m.This quantity of earth may be obtained only from 1.1 m depth of cutting. This limited depth of cuttingreduces the construction cost considerably. However, full consideration should also be given to thepossible effects of flood. The surface features of the area proposed for the pond or the farm is alsoequally important. A saucer-shaped area may be an ideal site for a large dug-out pond, because it mayhold appreciable quantity of water with a small amount of earthwork.

For smaller and flat areas eye estimation is enough, but for a big area proposed for farm constructionwith a number of ponds for different purposes and of different sizes, it is essential to conduct contoursurvey for determining the topography and land configuration. The site should be easily approachable sothat there may not be any difficulty in the transportation of input materials and in the marketing of theproduce. The labour and materials required for construction and operation should also be locally availableas far as possible. From an efficient management point of view the pond site should, if possible, be withinthe sight of the farmer's house. It also reduces the risk of poaching. Siting fish ponds near the farmer'sother agricultural or livestock farming activities makes it easier to integrate all the farming activities.

6.1.2 Source of water and its quality

A dependable source of water supply must be available within or near the site, even for undrainableponds. However, unlike drainable ponds, undrainable ponds require just sufficient water to fill the pondsand to compensate the water loss through seepage and surface evaporation thereafter. Equally important

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is the need for avoiding excess water and hence there must be arrangement for the excess water toescape through a bypass channel or a spillway. The water supply to the pond should as far as possiblebe natural, preferably rain water. However, alternative arrangements of water supply should be made fordry season either from a deep tube well or irrigation canal or from perennial sources like spring, stream,river, etc. Ponds should be on the lower lands to allow accumulation of surface runoff from a largercatchment area. However, care should be taken to provide proper bypass or spillway to avoid flooding. Ahigher subsoil water table due to irrigation in surrounding fields and percolation from artificial or naturalchannels, in addition to absorption from rain water, also helps in maintaining water level in undrainableponds (Sahoo, 1984).

The quality of the available water is also equally important for fish culture. Pond fish production isinfluenced by the physical and chemical properties of the water. Water should be clear as far as possible.Turbid waters which carry suspended solids cut the light penetration, thus reducing primary productivityof the pond. Excess of suspended solids also adhere closely to the gill filaments and cause breathingproblems. Water temperature also significantly influences the feeding and growth of fish. Prevailing watertemperature, ranging between 15°C and 35°C in tropical areas, is most suitable for carps. The chemicalquality of water depends on its content of dissolved salts. Rain water does not carry any dissolved salts.However, it collects nutrient salts from the ground surface of the catchment area. The water should beneither too acid nor too alkaline; neutral or slightly alkaline waters are most suitable for fish culture andhence acid water should be limed to make it neutral. Waters with pH values below 5.5 or over 8.5 are notproper for fish culture. The farmer will need huge quantity of lime to neutralize it while highly alkalinewater may cause the precipitation of both phosphate and iron, and if it remains continuously above pH 9,it may be harmful to fish.

6.1.3 Soil type

Pond soil must retain water. Soils with a low infiltration rate are most suitable for fish pond. Table 5shows the filtration rate of different types of soils. The best soils for our purpose are thus theimpermeable clay which can be easily compacted and made leak proof.

Table 5Infiltration rates of different types of soil (Stern, 1979)Soil type Infiltration rate (mm/ha)

Clay 1–5Clay loam 5–10Silty loam 10–20Sandy loam 20–30Sand 30–100

Loamy soils can also be used, but they need well compacting, and may leak slightly in the early stages,although they tend to seal themselves with time. Sandy and gravelly soils should be avoided, but if theyare the only ones available they must be made impermeable with a thick coating of clay or with polythenesheeting. Soil impermeability can also be achieved by soil compaction at the pond bottom and dyke witheither a mixture of soil + 1–5% cement or soil + 10–20% cowdung. Treated areas should be kept moistfor 2–3 days by gently sprinkling water to avoid cracking and finally the pond is filled with water (Sahoo,pers.comm.).

Peat soils have special problems, since they are usually very acidic in nature and need sufficient liming,while the organic matter decomposition may lead to dissolved oxygen deficiency. Soils rich in limestonealso create special problems, since the excessive lime content tends to precipitate phosphate and iron.Such ponds would then have little plankton population and macrophytes and would be relatively sterile.This can be overcome by adding sufficient organic matter such as cowdung, poultry manure, etc.

A general and convenient field test for the soil quality is to take a handful of moist soil from the test holesmade at the proposed site and to compress it into a firm ball. If the ball does not crumble after a littlehandling, it indicates that it contains sufficient clay for the purpose of pond construction. Accuratedetermination of the composition of the soil and its water-holding character is possible by hydrometer

method. Several test holes may be made across the site and soil samples may be collected verticallyfrom every 0.5 m of depth reaching up to a level of 3–4 m in a test hole. Using the results of the soil tests,a soil profile chart for the proposed site may be drawn. An arbitrary soil profile chart is presented (Fig. 12)showing the presence of clayey soil up to a depth of 3.5 m.

6.2 Designing

Based upon the survey on topography, soil type, water supply, etc., the detailed designing and layout ofthe ponds/farm are done. However, the following additional points are also to be considered.

6.2.1 Water area ratio among pond types

The production or stocking ponds are stocked with large size fingerlings of about 10–15 cm size in thecase of composite fish culture. To attain this size, the hatchlings are reared in much smaller andshallower ponds called nursery and rearing ponds for about 2–3 months. In the nursery ponds thehatchlings are reared up to fry stage and in the rearing ponds the fry are reared till fingerling stage. Theratio of water area among nursery, rearing and stocking ponds in a fish farm depend upon the basicobjective of the farm. In case of a fish seed farm, only nursery and rearing ponds are to be constructedwith a small area for few stocking ponds to be used for raising the brood fish, while in the case of fishproduction farm only stocking ponds are to be constructed for producing table size fish from fingerlings.The layout of a complete farm is given in Figure 13.

There is no hard and fast rule regarding the size of a pond. However, nursery ponds should be small andshallow. Ponds having 0.02–0.06 ha water area and 1–1.5 m depth are most suitable as nurseries.Rearing ponds are relatively larger, preferably between 0.06 to 0.10 ha in size and 1.5 to 2.0 m in depth.The sizes of stocking ponds vary tremendously. For newly constructed undrainable ponds, total waterarea of 0.25 to 1.0 ha is recommended (Table 6).

Figure 12. Soil Profile

Figure 13. Layout of a Fish Farm (Land area 3.6 ha)

In shallow ponds the water becomes heated easily. In deeper ponds light cannot reach the bottom. Invery deep ponds thermal stratification may occur with colder deoxygenated bottom layer. Dead planktonand faecal matter from fishes may fall on the bottom layer where the nutrients may be locked up.However, in case of rain-fed areas where the water table goes down during the dry season, the depthshould be kept around 3.0 – 3.5 m to store more water during the rainy season.

Although a square pond is economical to construct for its minimum length of dyke, a rectangular shape ofthe pond (length:width in proportion of 3:1) is considered to be ideal. In any case the pond width shouldnot exceed 30 to 40 m as it is difficult to operate a fishing net in broader ponds. The nursery and rearingponds may be square, since they are too small to pose any problem for netting. The corners must becurved to avoid fish escaping the net during harvesting. The layout plans of nursery, rearing and stockingponds are given in Figures 14A and 14B.

Table 6Practical size and depth of nursery, rearing and stocking ponds (Sahoo, 1984)

Pondtype

Size(ha)

Depth* (m)

Irrigated command/water loggedareas

Rainfed+/non-irrigated

areas

Nursery pond 0.02 – 0.06 1.0 – 1.5 1.5 – 2.0Rearing pond 0.06 – 0.10 1.5 – 2.0 2.0 – 2.5Stocking pond 0.25 – 1.0 2.0 – 2.5 2.5 – 3.5

* Excluding the freeboard+ May vary depending on impermeable strata at pond bottom

6.2.2 Dyke

The dyke should be properly designed so that it can hold maximum water in the pond and withstand thehydraulic pressure. The slope of the dyke usually depends on the type of soil. Suitable side slopes fordifferent soil types are given in Table 7.

Figure 14a. Design of Nursery, Rearing and Stocking Ponds

Figure 14b. Cross Section Details of Ponds

Table 7Suitable slopes for different soils

(Sahoo, pers.comm.)Soil type Soil (horizontal:vertical)

Clay 1:1 to 2:1Clay loam 1.5:1 to 2:1Sandy loam 2:1 to 2.5:1Sandy 3:1

Provision for a berm of sufficient width may also be provided for stabilizing the slopes. A wider berm alsohelps in operating the net in the pond. The berm should be 1 m or more in width (Saha andGopalakrishnan, 1974). The top width of the dyke should be decided taking into account its usage.Usually the minimum top width of the dyke should be 1.5 m. The wider crest requires not only a largerarea for dykes, but also an increased amount of earth material involving heavy expenditure. It is alwayswise to design the dyke as per the quantity of earth expected to be available from excavation work. A soil-type containing approximately 25% silt, 35% sand and 40% clay is most suitable for dykes. However, ifexcavated soil quality is not up to the above standard, provision may be made for a clay core to make thedyke watertight. While designing, about 10–12% allowance may be given for settling of earthwork (Fig.15).

6.3 Construction

Before initiating the construction work, proper estimates have to be prepared based upon the designdetails, which will include the cost of all the materials and the labour. Strict supervision is required atevery step of construction to ensure the adherence to specifications laid down in the design.

6.3.1 Time of construction

If the construction work is taken up at the most appropriate time or season of the year, the work becomeseasier and economical. The best time of the year for constructing ponds in clayey soil is post-rainy periodand winter when the soil is soft rather than at the end of the dry season when it is very hard. For swampy

and waterlogged areas the most desirable time is the late summer when the area becomes completelydry. However, if a pond is built during winter or early summer and is not filled immediately, weeds maygrow and cover the bottom. In such cases deweeding is needed before filling the pond.

Figure 15. Design of a Dyke with Core Well and Key Trench

6.3.2 Preparation of site

The site should be thoroughly cleared of all the trees, bushes, etc. Even the roots of trees should beremoved. No woody material should be left because the same will eventually rot and cause leaks. Sometree trunks rot very slowly and may cause problems during netting.

6.3.3 Marking the outlines

This operation involves laying out the features of ponds on the ground in order to mark out the areas fromwhere the earth will have to be cut and removed and also where earth will have to be embanked. Initially,lines are drawn according to the layout, followed by pegging and fixing stakes or posts. Strings arestretched between the tops of pegs and posts to mark the complete profile of the dyke with its correctheight, width and slopes (Fig. 16).

6.3.4 Pre-excavation work

Prior to pond excavation and dyke construction, all loose surface soil should be removed from about 20cm depth within the total outlined area of the dyke and the surface should be roughened by ploughing ordigging. In order to unite the body of the dyke to subsoil, it is desirable to dig a small “V” shaped keytrench (Fig.15). When the dyke is to be made on a sandy, gravelly or marshy soil base, the constructionof a key trench becomes essential and in such cases digging should be done until watertight foundationsare reached. The key trench is a small ditch or furrow dug along the line of the centre of the walls about0.5 m – 1.0 m wide and 0.5 m deep. This trench is filled in with a good clayey soil and is well rammed. Ifgood clayey soil is not available in the area, ordinary soil should be well compacted into the trench. Thepurpose of the trench is to stop seepage of water underneath the walls.

6.3.5 Pond excavation and construction of dykes

The excavation work can be carried out within the area marked for the pond bottom either manually ormechanically. However, the final levelling of the pond bottom and sides should be done manually withproper ramming and finishing as per the original design. The construction of the pond becomeseconomical if earthen dykes are made around the pond using the excavated earth from the pond bed. Alldykes should be raised, dumping the earth layer by layer stretching right across the whole section, and insuch cases each layer should not exceed 20 cm in thickness. All large clods should be broken and eachlayer should be thoroughly consolidated by watering and ramming. The sides and top of the dykes shouldbe properly dressed and finished with wooden thappies (wooden block with handle for ramming).

In case the soil quality is not suitable for making dykes, a clay core is provided in the dyke to make itwatertight (Fig.15). A mixture of 1:2 of sand and clay is used to make the clay puddle. This should beconsolidated, compacted and deposited in 10–15 cm thick layers. Each layer should be adequatelymoistened before the next layer is laid and precaution should be taken to prevent the puddle frombecoming dry and cracking.

Figure 16. Layout and Pegging before Pond Construction (Corner View)

Dykes must be well compacted to render them stable and the top should be rammed flat so that smallvehicles can also run along when needed. Short creeping grass is recommended to be grown on the topand sides of the dyke. Trees are not desirable since their dense shade inhibits the productivity of thepond.

6.3.6 Water inlet structure

Since we are concerned here with static and undrainable ponds, a feeder stream running directly into thepond should be avoided. The feeder stream must therefore be diverted along the side of the pond andfrom a suitable point water is channeled to the pond when required. An inlet structure should be providedthrough which water can be let into the pond. A proper inlet enables the quantity of water flowing into thepond, to be regulated, preventing the entry of undesirable fish and other aquatic animals and the escapeof stocked fish. For small ponds the best inlet structure is a galvanized iron pipe of about 10 cm diameterwith a control tap and a screen basket (Fig. 17 A). The downstream end of the pipe should be 30–40 cmabove the water level. A sluice is also suitable for this purpose, especially for larger ponds. A screen isalso fixed to check the entry of undesirable fishes and other animals (Fig. 17 B). To avoid scouring whenthe pond is being filled, a concrete apron can be built at the sluice, or more cheaply, a layer of gravel laid

down. Similarly, if water is let in with a pipe there should be a gravel bed laid down where the waterstream falls into the pond. If gravity feed is not possible, water must be pumped from the supply sourceinto the channel leading to the pond or even directly into the pond; but, in that case, the intake should besecurely wrapped by a firm net to prevent undesirable fish and other animals from entering into the pondalong with the water.

6.4 Maintenance

Proper maintenance of the pond and pond structure is most essential. Most of the earthen structures,especially the dykes, are susceptible to weathering action and hence they need periodical checks.Attending to minor damages regularly avoids the chances of more costly repairs later. The grass turfingneeds special attention. Proper and timely mowing prevents the formation of weedy growth and tends todevelop a root system more resistant to runoff. Erosion from the top during heavy rains causes groovingout of small channels and it is an indication that the top has not been properly consolidated. The areashould be levelled with more soil and thoroughly rammed and then grass should be planted to bind it.Side erosion at the dyke bottom may be due to a number of reasons. The worst damage is done bycommon carp. Erosion due to frequent wave action, particularly if the grass at the edge has been grazedby grass carp, can cause undercutting of banks and subsequent collapse of dykes. Some methods usedto provide protection against such erosion are earth berms, stone or brick pitching, stakes/bamboo piling(Fig. 18).

Figure 17A. View of an Inlet Structure

Figure 17B. Additional Detail

Surface washings and organic additions cause siltation which reduces the pond depth and pond fertility.The undrainable ponds should therefore be dewatered in the summer months at the interval of 5–7 years.This has already been described under Section 4.



More details

7. FISH SPECIES SUITABLE FOR CULTURE IN PONDSAlthough a large number of fish species grow successfully in ponds, only a restricted number of speciesare usually cultivated on commercial scale. Reasons for this restricted choice is obvious. Commercialpond culture basically aims at achieving maximum possible rate of fish production and profit throughoptimum utilization of the natural food and the supplementary feed which drastically limits the choice offish species for pond cultivation. Some of the basic criteria for selection are discussed below.

7.1 Criteria for selection of suitable fish species

Adaptability to undrainable pond environment

Faster growth rate

Efficient utilizers of natural food resources of the pond

Efficient converter of artificial feed

Hardy and not easily susceptible to disease

Easy to breed and rear the seed

Prolonged breeding period or multiple breeding frequency

Non-predaceous, planktophagous and preferably herbivorous and detritus feeder

Compatability with other cultivable species of fish

Palatable with high nutritive value

High market demand and high price.

To find all these qualities in one fish species would be very unlikely. Therefore, the species havingmaximum required traits are considered to be desirable for cultivation in undrainable ponds. Carps fit wellto these criteria and hence the most widely cultivated food fishes in South Asia are the quick-growing,non-predatory carps.

7.2 Fish species suitable for culture in undrainable ponds

There are two major systems of carp culture in Asia: the Chinese polyculture system where Chinesecarps are cultured together, and the Indian composite fish culture system where the Indian major carpsand Chinese carps are combined. In China, Chinese carps such as silver carp (Hypophthalmichthysmolitrix), grass carp (Ctenopharyngodon idella), bighead carp (Aristichthys nobilis), mud carp (Cirrhinusmolitorella), black carp (Mylopharyngodon piceus), and common carp (Cyprinus carpio) are culturedunder polyculture system in ponds. Under the Indian system of composite fish culture in undrainableponds, three Indian carps, viz. catla (Catla catla), rohu (Labeo rohita) and mrigal (Cirrhinus mrigala), twoChinese carps, viz. silver carp (Hypophthalmichthys molitrix) and grass carp (Ctenopharyngodon idella),and common carp (Cyprinus carpio) are extensively cultivated.

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Figure 18. Anti-erosion Meaasures

7.2.1 Catla

Catla is the fastest growing Indian major carp species and widely distributed throughout India, Nepal,Pakistan, Burma and Bangladesh (Fig. 19). It inhabits the surface layer of water and feeds upon plankton.Adult stages are predominantly zooplankton feeder, occasionally taking in decaying macrovegetation,

phytoplankton and smaller molluscs. It attains maturity in the second year of life and carry over 70 000eggs per kg body weight (Jhingran, 1966). It naturally breeds in rivers during monsoon season and undercontrol conditions in bundhs as well. It does not breed in ponds. However, it responds well tohypophysation techniques. Seeds are easily reared in undrainable ponds of relatively smaller size. Undercomposite fish culture in ponds it usually grows to over 1 kg in one year.

7.2.2 Rohu

Rohu is the natural inhabitant of river systems of India, Nepal, Pakistan, Bangladesh and Burma (Fig. 20).In recent years it has been transplanted to many countries of the world including Sri Lanka, Mauritius,USSR, Japan, Philippines, Laos, Malaysia and Thailand. Normally it occupies the column region of theaquatic ecosystem and feeds mostly on vegetable matter including higher plants, detritus, etc. Like catlait naturally breeds in rivers and under special conditions in bundhs. Except by hypophysation to which itresponds quickly, it never breeds in ponds. It attains sexual maturity during the second year. However,certain percentages of pond-reared specimens mature within one year. Fecundity varies from 226 000 toabout 2 800 000 depending upon the size (Khan and Jhingran, 1975). Rohu spawns during the monsoon(April—September). Seeds collected from rivers or produced by bundh breeding or induced breeding arereared with ease in seasonal or perennial undrainable ponds. Under pond culture conditions it grows upto900 g within one year.

7.2.3 Mrigal

Mrigal inhabits all the major river systems of India, Pakistan, Bangladesh and Burma (Fig. 21). The adultfish feeds upon filamentous green algae, diatoms, pieces of higher plants, decayed vegetable, mud anddetritus. It is basically a bottom feeder and hence suitable for cultivation with column and surface feedercarps in ponds. Mrigal usually attains maturity within 1 or 2 years depending upon the agroclimaticconditions of the location. Fecundity ranges between 124 000 to over 1 900 000 depending upon size.Spawning season is linked with the onset and duration of the southwest monsoon. It does not breed inponds, but can be easily bred in bundhs and by hypophysation. It is now being induced to breed twicewithin the same spawning season. Rearing of seed is usually undertaken in seasonal or perennialundrainable ponds. Under pond culture conditions it grows to over 1 kg in one year.

Figure 19. Catla (Catla catla)

Figure 20. Rohu (Labeo rohita)

Figure 21. Mrigal (Cirrhinus mriqala)

7.2.4 Silver carp

Silver carp is basically inhabitant of major river systems of South and Central China and in the AmurBasin of USSR from where it has been transplanted throughout the Indo-Pacific region including India. Itis a surface dweller feeding mainly upon zooplankton during its early stages and gradually becomespredominantly a phytoplankton feeder. Its relatively longer branchiospines provide a fine filter capable ofretaining planktonic organisms. It readily accepts supplementary feed like oil cakes and rice bran mixturein pond culture systems. It does not breed in pond condition. However, through the technique ofhypophysation they are induced to breed in ponds during the monsoon season (Section 8.1 of thismanual). Fecundity varies greatly with the size and agroclimatic condition. A fecundity range of 145 000to 2 044 000 has been found from silver carp (Alikunhi, Sukumaran and Parameswaran, 1963). It takesabout 2–6 years to mature in China, whereas in India it matures very early, within 2 years. Males matureearlier than the females. In composite fish culture ponds it usually attains over 1.5 kg within one year ofrearing. Seed rearing is done in smaller seasonal or perennial undrainable ponds with a high rate ofsurvival (Fig. 22).

Figure 22. Silver Carp (Hypophthalmichthys molitrix)

7.2.5 Grass carp

Grass carp is a native of the river systems of South-Central and North China, and the Amur river ofUSSR. Its suitability in aquaculture and biological control of aquatic weed infestation has resulted in wide-scale transplantation throughout the world. In early life it feeds on planktonic organisms and graduallyswitches over to macrophytes. They are voracious eaters and show distinct preference for vegetable foodmaterials such as grass, leaves, weeds, etc. However, they also accept supplementary artificial feedmaterials. Usually only a portion of ingested food is digested and the rest is voided in semidigested orundigested form which, in turn, becomes choice food for the bottom dweller common carp (Alikunhi,Sukumaran and Parameswaran, 1963). In China it takes about 3–4 years to achieve maturity whereas inIndia it usually takes 2 years. The total number of eggs range between 308 800 and 618 100 from thefishes weighing between 4.7 kg to 7.0 kg. The fish does not breed under pond condition and hence seedproduction is achieved through hypophysation. Growth mainly depends on the rate of feeding. Underoptimum feeding rate it can grow over 5 kg in one year (Sinha and Gupta, 1975). Usually it grows to over1.5 kg in composite fish culture ponds (Fig. 23).

Figure 23 . Grass carp (Ctenopharyngodon idella)

7.2.6 Common carp

Originally a native of temperate region of Asia, especially China, the common carp is now the mostdomesticated and cultivated carp species throughout the world (Fig.24). It is an omnivorous bottomdweller subsisting mainly on benthic fauna and decaying vegetable matter. It frequently burrows the pondbottom in search of food. This habit of digging the pond bottom helps in maintaining the productivity ofundrainable ponds and hence culture of common carp with other carp species is of great advantage.Moreover, it also feeds directly on the undigested excreta of grass carp. Growth mainly depends upon thebottom biota, stocking density and the rate of supplementary feed. In composite fish culture ponds itgrows to about 1 kg within one year. In a tropical climate it spawns throughout the year in the pondenvironment with two peak periods, one from January to March and the other during July and August.

Eggs are small and adhesive in nature. In tropical conditions it attains maturity within 12 months(Alikunhi, 1966).

Figure 24. Common carp (Cyprinus carpio)

Produced by: Fisheries and Aquaculture Department


More details

8. PROCUREMENT OF INPUTSSeed, feed and fertilizers are the three major inputs of undrainable pond culture systems. Paucity of quality fish seed is even nowconsidered as one of the major constraints in the development of freshwater carp farming. This is mainly due to the large-scaledevelopment of this farming system creating ever-increasing pressure on carp seed industry. However, construction of large- and small-scale carp hatcheries has provided enough support to this industry during recent years. Ideally, a farm should be self-sufficient withnursery and rearing ponds so that after meeting their own demand the surplus seed can be sold for additional farm income. Small,seasonal, undrainable village ponds are most suitable for this purpose. Procurement of feed is not a problem as most of the feed materialsare village-based agro-industrial products and by-products and are readily available in villages and local markets. Only some feedadditives are needed to be procured from towns. Animal manures are incidental to village-based allied agricultural and animal husbandryactivities while fertilizers are readily available in the local markets throughout the year.

8.1 Procurement of seed

Except common carp, all the other five Indian and Chinese major carps, viz. catla, rohu, mrigal, silver carp and grass carp, cultivated undercomposite fish culture do not breed in pond conditions although they attain full gonadal maturity. However, they breed in bundh type tanks.The successful development of the technique of induced breeding through hypophysation ensures breeding of both Indian and Chinesemajor carps in captivity. Therefore the stocking materials are procured from three different sources, viz. collection by traditional methodsfrom rivers, by induced breeding of carps and by breeding in bundh-type tanks.

8.1.1 Collection of spawn from riverine sources

The technique of spawn collection from rivers essentially consists of operating fixed filtration nets in marginal areas of flooded rivers duringmonsoon months, when the Indian major carps normally breed. Success of operations mainly depends on proper sites, suitable nets,monsoon flooding patterns, availability of sufficient brood stock and the success of spawning.

8.1.1.1 Spawn net and its operations

These are funnel-shaped nets made of fine mesh (1.5 to 3.0 mm) handloom nettings (Figs. 25a and 25b). The posterior end has a smallround opening fixed on a bamboo ring. A small trough-like receptacle (gamcha) is tied to the ring where live spawn is collected. The net isfixed in marginal waters where depth of water is negotiable without any aid. River margins with gradual slopes are the most suitable sites.Water flow in the range of 20 to 60 cm/sec is desirable.

Figure 25a. Collection of Riverine Spawn

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Figure 25b. Riverine Spawn Collecting Net

8.1.1.2 Site selection

A premonsoon survey should be conducted to collect the following details, based upon which the suitable site is selected.

1. The topography and terrain and river bank features in the vicinity of a site to determine the extent of area available for operating netsat different flood levels.

2. Topography of dry beds and bank features to know the likely current pattern of the river at different levels of flooding.

3. The distribution and composition of the fish fauna in the selected stretch of the river for assessing the resident population of Indianmajor carps.

4. Location of tributaries, streams, etc., along with their confluence with the main river as these may be connected with the breedinggrounds.

5. The accessibility of the site.

Spawn availability is mostly associated with receding phases of floods.

8.1.1.3 Collection operation

To assess the availability of spawn, initially 2–3 spawn nets should be operated constantly at suitable sites and the whole battery of netsshould then be introduced as soon as the spawn become available. The nets should be fixed along the river margins with the help ofbamboo poles and are adjusted according to changes in flood level. At every four hours, the nets should be removed, cleaned and refixed.

The flowing spawn are collected in the receptacle (gamcha) from where they are scooped every 15 to 30 minutes, depending on theamount of spawn being collected. The collected spawn along with the bigger fishes, debris, etc., should be scooped from the receptacle(gamcha) and transferred to aluminium containers (hundies) half filled with water. The collection should then be sieved through roundmeshed mosquito netting to segregate spawn from debris and larger fishes, and the spawn should be conditioned in hapas (clothcompartments fixed in water) before they are transported. Measurement of spawn should be done by special sieve cups (Fig.26). Usuallyearly spawn measures about 500 individuals/ml. The seed collected from rivers are generally a mixture of seeds of major carps, minorcarps, predatory fishes, etc.

Figure 26. Sieve Cup for Measurement of Spawn/Fry

8.1.2 Bundh breeding

Bundhs are special types of perennial and seasonal tanks or impoundments where riverine conditions are simulated during monsoonmonths. The bundhs are ordinarily of two categories, viz., a perennial bundh commonly known as “Wet bundh” and a seasonal one called“Dry bundh” (Mookherjee et al., 1944) (Figs. 27A and 27 A-1, 27B and 27 B-1).

8.1.2.1 Wet bundh

A typical “Midnapore type” of wet bundh is generally located in a gradual slope of a catchment area with an inlet towards the high land andan outlet at the opposite side towards the lower end to regulate the inflow and outflow of water respectively during heavy showers.

The wet bundh contains a deeper area which retains water throughout the year and where adequate stocks of brood fishes are maintained.During heavy rains, a major portion of the bundh is submerged and excess water, if any, is drained through the outlet which is guarded bybamboo fencing (locally termed as “Chhera”). The shallow areas of the bundh (moans) serve as breeding ground for fishes present in thebundh.

The wet bundh varies in shape and size from place to place. Generally, the ponds covering a water body of 1–2 ha with catchment arearanging from 20–100 times are considered as wet bundhs, but a bundh could be as large as 300 ha.

Figure 27A. Bundh for Breeding (Wet Type)

Figure 27A-1. Bundh for Breeding (Wet Type)

Figure 27B. Bundhs for Breeding (Dry Type)

Figure 27B-1. Bundhs for Breeding (Dry Type)

8.1.2.2 Dry bundhs

This type of dry bundh consists of only one shallow depression (or one shallow pond) and a catchment area located in a gradual slope.The upper high land area is considered as a catchment area. The shallow depression or pond is enclosed by embankments on three sideswhich impounds freshwater from the catchment area during the monsoon season. There should be provision for an outflow for drawingexcess water from the pond during heavy rains. The outlet is guarded by fine bamboo fencing. Such bundhs remain more or less dry duringthe greater part of the year. In the West Bengal Province of India, a catchment area more than five times the size of the bundh isconsidered most suitable (Saha et al., 1957), whereas in Madhya Pradesh the recommended ratio is 1:25 (Dubay and Tuli, 1961). Drybundhs of Madhya Pradesh are comparatively bigger in size (0.2 to 2.5 ha) than those of West Bengal (0.1 to 0.5 ha).

In a modified bundh, adjacent ponds are constructed along the gradient of the catchment area (Moitra and Sarkar, 1973, 1975). The upperone where the premonsoon rain water is collected from upland catchment area serves as a “reservoir” and the lower one is used forbreeding purposes. A deeper tench is dug along the lower extremity of the breeding bundh so that the breeders can take shelter beforeand after spawning. The reservoir and breeding bundhs are arranged in a sequence along the gradient so as to facilitate the flow of waterwhich is controlled through a system of sluice gates. Premonsoon rain water is collected from the catchment area to fill up the reservoir.The water-holding capacity of the reservoir is generally more than that of the breeding ground bundh.

8.1.2.3 Breeding operation

Wet bundh: With the onset of monsoon the fresh rain water from the catchment area enters into the bundh and the latter is inundated.The excess water flows out from the bundh creating a water current. The breeders present in the deeper area of the bundh migrate toshallow areas where they start breeding.

Dry bundh: Rain water which accumulates in the catchment area during premonsoon showers flows in to fill up the pond seasonally.Thereafter, the brood fishes from a perennial pond are introduced into the seasonal ponds to breed, preferably on cool rainy days.Spawning usually commence during and after heavy showers when the bundh as well as the catchment area are flooded with freshrainwater.

In a modified method adopted in Bankura and Midnapore districts of West Bengal, some fresh water is released from the reservoir into thebreeding bundh. Gravid carps from the perennial ponds are then transferred to the breeding bundh. Generally, the ratio of male and femalespawners is maintained at 1:1, but sometimes this proportion is not strictly followed. The spawners are allowed to remain for 10–12 hoursin order to get acclimatised to the environment. A few sets of males and females are then selected and taken out from the bundh andplaced in separated mosquito net hapas, which are cloth compartments fixed in water with the help of poles at its four corners (Moitra andSarkar, 1973, 1975). The selected female breeders are taken out of the hapas and injected intramuscularly with fresh pituitary extract. Thefemales are administered an initial dose of the extract at the rate of 3 mg/kg body weight and thereafter kept again in mosquito net hapas.After 4–5 hours, the second dose (8 mg/kg) of extract is injected to the female. At the same time the males are given the initial dose of theextract at the rate of 3 mg/ kg of body weight. The injected spawners are then released into the breeding bundh. After administration of thesecond dose of extract to the females, the inlets and outlets of the bundh are lifted to allow the entry of a steady flow of water from the

reservoir into the breeding bundh soon after breeding takes place. In one such bundh 5–6 breeding operations can be taken up in oneseason, subject to availability of spawners and fresh water. Before starting the next breeding operation in the same bundh, the water iscompletely drained out and it is allowed to dry.

Exotic carps such as grass carp and silver carp have also been induced to breed in the dry bundhs of West Bengal by applying pituitaryextract and under regulated water flow (Sinha et al., 1975).

Collection of eggs: Egg collection is taken as soon as the embryo starts twitching movements. To collect eggs, the water level of thebundh should be lowered by opening the outlet. Eggs are generally netted by a piece of thin cotton cloth (gamcha) or a piece of mosquitonetting cloth. In such areas a series of earthen pits are constructed with water flow facilities. Fertilized eggs are allowed to hatch in thesepits and the spawn are collected after three days. Spawn are usually sold at the bundh site.

8.1.3 Induced spawning by hypophysation

As an alternative method, use of hormones for inducing spawning in Indian major carps has been in practice for the last three decades.The gonadotropic hormones secreted by the pituitary gland of fish play an important role in the process of maturation and spawning. Asdiscussed earlier, under pond culture conditions, the carps do not spawn, although they attain maturity. This is due to the fact that thepituitary gonadotropic hormones which induce spawning are not released in sufficient quantities from the pituitary gland (hypophysis) to thegeneral blood circulation so as to trigger spawning. Therefore, for induced spawning, the hypophyseal hormones extracted from thepituitary of donor fish are injected into the sexually matured fish under favourable water and climatic conditions during the monsoonseason.

In India, the first success of induced spawning by hypophysation of Indian major carps was achieved by Chaudhuri and Alikunhi (1957).Subsequently, silver carp and grass carp were also bred in 1962 (Alikunhi et al., 1963). This outstanding success in induced spawning ofAsiatic major carps has revolutionized carp culture practice through commercialization of carp seed production.

Pituitary gland of major carps and its collection:

The pituitary gland or hypophysis of Asiatic major carps is a small, pear-shaped, whitish soft body, situated on the ventral side of the brainbelow hypothalamus, which is connected to the pituitary gland by a funnelshaped structure, the infundibulum. The quantum ofgonadotrophic hormones in the pituitary vary with the season and maturation stages of the fish and hence the degree of success achievedin induced spawning depends very much upon the condition of the pituitary gland of donor fish. Based on a series of experimental trials ithas been found that the maximum success in induced spawning is possible with extracts prepared from gland collected during May/June,i.e. the period just before spawning (Moitra and Sarkar, 1978). Thus the pituitary glands for the induced spawning programme shouldpreferably be collected from the freshly killed fully matured specimen of both the sexes of the same (homoplastic) or allied species(heteroplastic) during May/June when the potency of the gland remains at its peak. Well preserved iced fish are also suitable for thispurpose. Common carp, a perennial breeder, has been found to be an excellent donor fish as the potency of the gland remains more orless high throughout the year. Both male and female donor fish are suitable for gland collection.

8.1.3.1 Collection of gland

The commonly adopted method of gland removal is by chopping off the skull with a sharp butcher's knife or a hand saw. The brain thusexposed is lifted up by detaching the optic nerve. Excess of watery fluid and the blood is soaked by absorbant cotton and then themembrane covering the gland is cautiously removed by using a needle and a pair of forceps. The gland thus exposed is picked up verycarefully avoiding any damage (Fig. 28). Broken or damaged glands lose their potency due to hormonal drainage. In India, in fish marketswhere a large number of fish heads are sold separately and the consumers strongly dislike dissected fish heads for consumption, theglands are taken out from behind the head through the foramen magnum. The technique of removing glands by this method is simple andquick. Behind the head there is a big hole in the brain case known as the foramen magnum. The brain tissues are removed through thisforamen magnum and then by close examination the gland is located embedded in the floor from where it is scooped out carefully with thehelp of a small scooper.

Figure 28. Collection of Pituitary Gland

8.1.3.2 Preservation and storage of glands

Freshly collected glands have been found to be the best for the induced breeding purpose. But when we need a large number of glands totake up breeding on a commercial scale, it is not always possible to sacrifice so many matured fish for the required quantity of glands.

Such limitations dictate large-scale collection and preservation of glands from fish markets. There are several methods under use for thepreservation of pituitary glands, the most popular being the preservation in absolute alcohol and after an interval of 24 hours they are dried,weighed and transferred to dark coloured phials containing fresh absolute alcohol. Alcohol dehydrates and defattens the glands. Detailsabout the place and date of collection, the age and weight of the donor fish, etc., should be labelled on the phials for ready reference. Thephials are then kept at room temperature or in a refrigerator. When needed the stored glands are put on filter paper which allows thealcohol to evaporate, and are then weighed accurately. However, better results have been achieved from glands preserved in acetone.Immediately after collection the glands are kept in fresh acetone and placed in a refrigerator. After two days the glands are taken out,weighed and replaced in phials with fresh aceton. Such phials are labelled and placed in a refrigerator until use. The glands can also bekept frozen. Fresh glands are frozen immediately after collection and kept in a refrigerator, deep freezer or in insulated cans containing dryice.

8.1.3.3 Preservation of pituitary extract

Pituitary extract is normally prepared just before administration as such extracts cannot be kept long. However, there are certain simplemethods for the effective preservation of pituitary extracts. The advantage of extract preservation is that the preserved material remains inthe ready-to-use form which is very convenient, especially in villages where most of the basic facilities like precision balance, tissuehomogenizer, distilled water, centrifuge, etc., for extract preparation are not available. Besides, extraction from a large number of glandsalso ensures uniform hormone potency per unit volume of extract. In such cases it is always desirable to ascertain the potency of suchextract through several breeding trials before initiating a large-scale breeding programme.

Fish pituitary extract is prepared in distilled water-glycerine media at a concentration of 40 mg of gland for every ml of media. A knownquantity of glands is taken and macerated in a tissue homogenizer. Distilled water equal to one-third of the total volume of extract is addedto the fully macerated glands and thoroughly mixed. Pure glycerine, twice the volume of the distilled water, is then added. Thus the ratio ofdistilled water to glycerine is maintained at 1:2. The entire suspension is again thoroughly mixed and filtered through filter paper to removetissue fragments if any. Prepared extracts can either be ampouled in ampoules of various capacities or may be kept in small phials in arefrigerator. Such extracts should be consumed within one breeding season.

8.1.3.4 Brood stock maintenance and their selection for spawning

The two major inputs of induced breeding programmes through hypophysation are the pituitary glands and the properly matured spawners.Success of hypophysation also depends on the condition of the spawner and hence proper attention must be paid to raise quality broodstock in adequate numbers. Preferably 2–3 years old healthy male and female carps should be selected and reared in well prepared pondsof 0.2 to 0.5 ha with minimum water depth of about 1.5 m. The stocking density should be kept at a relatively lower level ranging between 1500 – 2 000 kg/ha. Normal pond management schedules are to be followed strictly involving weed clearance, removal of predatory andweed fishes, pond fertilization and application of supplementary feed, fish health care and monitoring of pond environment. Details aboutpond management are given in subsequent sections of this manual. Supplementary feed consisting of 1:1 oil cake and bran mixture shouldbe applied daily at the rate of 1–3% body weight on underwater feeding plates. The addition of 15–20% fish meal, vitamin and mineralmixture to the conventional feed gives better results. For grass carp, aquatic weeds such as Hydrilla, Najas, duck weeds, etc., or greenanimal fodder such as napier grass, hybrid napier, barseem, etc., are to be provided at the rate of 20–25% of their body weight on a dailybasis. The fish should be periodically netted and examined carefully to find out the stage of maturity and state of health. This rearing periodnormally lasts for 4–5 months. Proper care during this period ensures availability of well matured quality spawners for induced breedingprogrammes. It is estimated that for a target production of about 10 million spawn (6 million of Indian major carps and 4 million of silvercarp and grass carp) about 750 kg of brood stock (300 kg of Indian major carps and 450 kg of silver carp and grass carp) comprising bothmales and females in a ratio of 1:1 by weight and 2:1 by number are required.

Usually after the onset of the monsoon when there is an accumulation of fresh rain water in the pond and a fall in atmospherictemperature, the breeding programme is taken up. The southwest monsoon period is the normal breeding season for these Asiatic carps insouth Asian countries and usually extends from April to September. In some places the monsoon is early and hence the breeding seasonstarts from April onwards. By seining the pond, spawners are caught and carefully examined for selection. Matured males ooze a milkyfluid (milt), if the abdomen is slightly pressed near the vent. They are also characterized by the roughness of their pectoral fins. Maturedfemales have a soft bulging abdomen with slightly swollen and reddish vent. A catheter is found to be quite helpful especially in the case ofsilver carp and grass carp in selecting the matured female breeders by examining the condition of the eggs. By inserting the catheter in thegenital opening of a female spawner, some eggs are taken out and examined at the pond site in a petridish. Uniform size eggs of pale bluecolour in silver carp and brown or copper colour in grass carp indicate proper maturation stage. Cool rainy days when the watertemperature ranges between 25°C to 30°C are considered to be ideal for induced breeding. Ripe and healthy males and females of desiredspecies are selected from the brood stock ponds, their individual weights are recorded using hand nets and a spring balance and thefemales are kept ready for the first injection of the pituitary gland.

8.1.3.5 Induced breeding operation

After the selection of brood fish the injectable dosage of pituitary extract is calculated in terms of milligram of pituitary gland per kg bodyweight of the recipient fish. Females are given two injections at an interval of 4–6 hours while males are given only one injection at the timeof the second injection to the females. Considerable variations are noticed in the effective dosage of pituitary extract which depends mostlyon the potency of the pituitary gland, gonadal maturity of the recipients and the prevailing climatic conditions. It has been experienced thata lower dosage is effective when extract is prepared from fresh glands while a higher dosage is required when commercially suppliedglands are used for the purpose. The first and second dose in the case of females of Indian major carps may be given at the rate of 2–4mg/kg and 5–10 mg/kg body weight respectively. The males are given only one injection at the rate of 2–4 mg/kg body weight at the timeof the second injection to the females. Silver carp and grass carp females should be given at the rate of 3–4 mg/kg body weight during theinitial injection and 8–10 mg/kg body weight during the final injection. Males receive only one injection at the rate of 3–4 mg/kg bodyweight. However, as stated the dose of the pituitary may be slightly increased or decreased depending on the local climatic conditions,potency of the gland and the response of the spawners.

After deciding on the dosage, the quantity of glands required for injecting the selected brood fish is calculated. Both ready-to-use bottled orampouled extract or freshly prepared extract can be used. For the preparation of fresh extract the required quantity of glands should betaken out, blotted, dried and weighed accurately. The glands are then macerated in a tissue homogenizer with a small quantity of distilledwater and further diluted so that each ml of the extract should be eqivalent to 20–40 mg of pituitary gland. The extract is thereaftercentrifuged to get rid of tissue fragments and only the supernatant solution is utilized for the injection.

The spawners should be grouped into several sets. Each set should consist of both female and male spawners in the ratio of 1:2 and

approximately 1:1 in weight. The required number of breeding hapas at the rate of one hapa for each set should be fixed in the pond. Abreeding hapa is a rectangular cloth container (2.5 x 1.5 x 1.0 m) closed from all sides except an opening on one side with tyingarrangements, through which spawners are introduced and taken out (Fig.29). These hapas should be fixed in the shallow waters of ponds,canals, lakes, and reservoirs with the help of bamboo poles in such a way that two-thirds of it are submerged in the water. Modern facilitiessuch as breeding tanks of metal, cement, fibre glass, etc., or plastic pools with continuous supply of water having controlled temperatureensure greater efficiency and operational ease.

Figure 29. Breeeding Hapas in a Pond

Intramuscular or intraperitoneal injections are administered. Intramuscular injections are commonly given in the caudal peduncle regionavoiding the lateral line. In the case of intraperitoneal injection the needle is pushed with ease at the innerside base of the pectoral fins. Forintramuscular injection, the needle is inserted under the scale initially parallel to the body of the fish and finally pierced into the muscle atan angle of 45° (Fig. 30). The most convenient hypodermic syringe used for the purpose is of 2 ml capacity having 20 divisions. The size ofthe needle for the purpose is also important which depends on the size of spawner to be injected. The BHD needle No.22 is convenientlyused for 1–3 kg of carp breeders and No.19 for larger ones. Needle No.24 can be used for small size spawners.

Figure 30. Injecting a Dose of Breeding Hormone

The induced breeding work is generally taken up on cool and cloudy days when the water temperature is around 25–30°C. It is alwaysconvenient to apply the first injection between 16.00–17.00 hours and the second injection after 4–6 h of the first injection i.e. between 20–23 hours. In the case of mrigal it is desirable to keep this interval of only 4 h. After the first injection to the female spawners, both malesand females of the set are released in the breeding hapa or the breeding enclosure. At the time of the second injection both males andfemales of the set are taken out, injected as per prescribed doses (Table 8), and released back in the breeding hapa.

Table 8Doses (mg of pituitary extract/kg body weight of spawners) and injection achedules for hypophysation

Injection Time of injection(h)

FemaleIMC

spawners*

GC/SCMaleIMC

spawners*

GC/SC1st 16.00–17.00 2–4 3–4 - -2nd 20.00–23.00 5–10 8–10 2–4 3–4

* IMC - Indian major carp; GC - Grass carp; SC - Silver carp

Breeding normally takes place within 3–6 h after the second injection. Recent investigation of Sinha (1972), has indicated that gonadalhydration is a prerequisite for successful spawning of carps. Gonadotropins induce the hydration process thereby increasing the bodyweight of the spawners, and thus serving as an indicator for the success or failure of the breeding programme. A 3% increase in bodyweight of female spawners between the two subsequent injections indicates better breeding success. The eggs are released by thefemales in the early morning hours and are fertilized naturally inside the hapa by the milt released by males. The brood fishes are removedfrom the hapas and the eggs which are non-adhesive and semibuoyant swell like small pearls of 3.5 – 5.5 mm in diameter. The totalquantity of good eggs laid is estimated from the total volume of eggs and percentage of fertilization. Fertilized and viable eggs aretransparent in colour while dead ones appear opaque under naked eye. Percentage of fertilization is scored from several egg samplesexamined in a petridish or watch glass. Silver carp and grass carp normally do not release eggs inside a hapa or a breeding enclosureeven after being injected with hormone and hence these fishes have to be stripped and fertilized artificially. The females are examined 3–4h after the second injection to see their readiness for stripping. Keeping the ventral side up and by giving a slight pressure at the genitalopening, if the eggs are seen oozing out, the fish is considered to be ready for stripping. Otherwise they are released back and examinedagain after an interval of 1/2 – 1 h. Usually, the dry method of stripping is adopted where the spawners are wiped with a towel and then thefemale spawners are stripped and the eggs are collected in dry enamel basins and immediately fertilized with stripped milt from the malespawners. At this stage the eggs and milt are mixed thoroughly for 1–2 minutes with the help of a clean feather and subsequently the eggsare washed 3–4 times with water. The fertilized eggs are then kept in breeding hapas for a few minutes for proper swelling and hardening.The usual quantity of eggs obtained from Indian and Chinese major carps under field conditions are presented in Table 9. It has beenobserved that in silver carp males the quantity of milt is insufficient and hence extra males should also be injected to ensure maximumfertilization of stripped eggs.

Table 9Quantity of eggs obtained from cultivated carp species

Species of carp Approximate number of eggs/kg body weightCatla 125 000 – 200 000Rohu 250 000 – 300 000Mrigal 150 000 – 200 000Silver carp 100 000 – 150 000Grass carp Around 100 000Common carp 150 000 – 250 000

8.1.3.6 Incubation of eggs and hatching

The eggs are measured by a graduated enamel or plastic mug of 1–2 litre capacity and collected in plastic buckets. From the plasticbuckets eggs are collected with the help of a 1 litre mug and spread uniformly at the rate of 3–4 litres of eggs in double-walled hatchinghapas fixed in ponds free from algal bloom, and predatory fish species (Table 11). These double-walled hapas are open from the upperside. The outer hapa is made of thick cloth or very fine meshed nylon cloth while the inner one is made of round meshed mosquito nettingcotton/nylon cloth. The dimension of various hapas are given in Table 10.

Table 10Dimension of breeding and hatching hapas

Type of hapa Dimension (m) SpecificationsLength Width DepthBreeding hapa 2.5 1.25 1.0 closed from all sides except at the opening with tying arrangement. Thick cotton/nylon cloth.Hatching hapa Outer 1.8 1.0 1.0 Upper side completely open. Thick meshed nylon/cotton cloth. Inner 1.5 0.8 0.5 Upper side completely open. Round mosquito netting of cotton/nylon cloth.

The number of eggs to be spread in each hapa depends on the size of the eggs of the species concerned. The following table will behelpful in deciding the amount of eggs to be incubated in a hapa.

Table 11Quantity of eggs of cultivated carp species to be incubated in each hapa

Species No. of eggs/1 (Approx.) Amount of eggs in 1/hapaCatla 22 000 – 25 000 4.0Rohu 28 000 – 30 000 3.0Mrigal 26 000 – 30 000 3.0Silver carp 22 000 – 25 000 4.0Grass carp 22 000 – 25 000 4.0

Hatching time is temperature dependent. Usually hathing takes about 15–18 h at temperature range of 26–31°c. At lower temperature thehatching time is considerably larger. The hatchlings pass out through the mesh of the inner mosquito netting hapa to the outer hapa. Whenhatching is completed, the inner hapa with egg shells is removed and the hatchlings are left undisturbed in the outer hapa for three days tillthe yolk sac is completely absorbed and the spawn become ready for stocking in nursery ponds. Common carp and other unwanted fishwhen present in the pond have been reported to cause severe damage to carp eggs in breeding hapas (Tripathi, 1975). The use of 1/4inch mesh size drag net as a barrier to prevent common carp from destroying fertilized eggs in breeding/hatching hapas may be a suitableway to solve the problem of those fish farmers who have only one pond and utilize it for composite fish culture (Radheyshyam, Sarkar andSingh, 1985).

The hatching technique described above has, however, several drawbacks and large-scale mortality and loss of developing eggs andhatchlings may occur due to natural hazards such as a sudden rise of water temperature, development of algal bloom, depletion ofdissolved oxygen, presence of predatory crustaceans, etc. With a view to improving the hatching technique and reducing mortality ofhatchlings, a glass jar hatchery has been designed by the Central Inland Fisheries Research Institute (CIFRI) and found to be very usefulin terms of percentage survival of hatchlings. Water hardened eggs are incubated in vertical hatching jars where the flow of water is soregulated during the incubation that the eggs are gently stirred without being spilled over. In each jar of 6.35 1 capacity, 50 000 eggs canbe kept for hatching. Normally the rate of flow of water is kept at 600–800 ml/min for Indian major carps and 800 – 1 000 ml/min for

Chinese carps. It normally takes 12–15 h for the developing eggs to hatch out in Indian conditions. Various modifications of this hatcherysystem are now available and extensively used. Chinese hatchery system consisting of cisterns with diagonally pointed nozzles as waterinlets and outlet with filtering screen and valve are also becoming popular. It requires a large volume of water with sufficient pressure tocreate a circular water current in the hatching cistern. 700 000 to 1 200 000 fertilized eggs can be used per cubic meter of water. Spawnare collected through drainage outlet.

8.1.3.7 Post-spawning care of brood fish

It should always be remembered that spent carps are potential breeders for the next breeding season and hence they should be savedand properly cared for. Before releasing them back in the pond they should be given prophylactic antibiotic treatment. Streptomycinsulphate and penicillin at the rate of 25 mg/kg fish and 20 000 I.U./kg fish respectively in the form of injection has been found to be veryeffective in preventing post spawning bacterial infections and subsequent mortality. Before releasing them back to ponds they should alsobe given a dip treatment in potassium permanganate solution to prevent any fungal attack. In the case of silver carp and grass carpfemales, where stripping is the normal practice, recovery from shock and severe stress is difficult under Indian condition and hence theyshould not be released back into the broodstock pond. However, if the stripping is easy and fast, both the males and females can bereleased after giving the similar prophylactic treatment. Use of anaesthetics during stripping minimises shock and stress and brings ease instripping operation.

Multiple breeding: Under natural conditions, Asiatic major carps breed only once a year. However, in recent years it has been possibleto breed them twice in a year. They are induced to breed in the early part of the season, well cared and well fed for the rest of the seasonand during the end of the breeding season they are again induced to breed by the same techniques. The interval between the two breedingoperations may vary from 30 to 60 days.

8.1.4 Production of common carp seed

Common carp is the only fish cultivated under composite fish culture which naturally breeds in ponds throughout the year in Indianconditions with two peaks of spawning, one during January to March and the other during July/ August. The females deposit sticky eggs onleafy vegetation in the pond which are immediately fertilized by the males. Although they breed naturally in the ponds, the survival of spawnis always poor and hence they should be induced to breed under controlled conditions as per the following successive steps.

8.1.4.1 Segregation and care of mature fish

Healthy and matured male and female brood fish should be segregated and kept in separate ponds usually by April and October. A maturemale easily oozes milt when the abdomen is gently pressed. The female on the other hand has a bulging abdomen with a papilla-likeoutgrowth with a median slit in the vent region. Segregated brood fish should be fed daily at the rate of 3% of their body weight.

Although they breed several times during the year, breeding should be taken up during mid-January to March and again during July-August.

8.1.4.2 Breeding technique

Fully mature male and female brood fish are selected for breeding and kept either in breeding hapas or cement cisterns. Breeding hapasshould be fixed in the shallower region of the pond with the support of bamboo poles. A set of spawners consisting of one female and twosmaller males more or less equal to the weight of the female are released in each breeding hapa. Sufficient quantity (double the weight ofthe female fish) of fresh aquatic weeds such as Hydrilla, Najas, Eichhornia (water hyacinth), etc., are also introduced in the hapa anduniformly spread. Fish usually spawn within 10–12 hours. Spawned breeders are then taken out and given prophylactic antibiotic treatmentand released back to the pond. The difference in weight of the female before and after spawning gives the estimate of eggs released. Eachgram of ovary contains about 700 eggs (Alikunhi, 1966). An allowance of 12–15% should be given for faecal droppings. By examiningseveral samples of eggs, the percentage of fertilization can also be estimated. Fertilized eggs are dirty pale in colour and more or lesstransparent, whereas unfertilized eggs are opaque and whitish in colour. The weeds with attached eggs should be transferred to thehatching hapas (Fig. 31) fixed in the pond. About 1 kg of weed with attached eggs should be kept in each hapa. The incubation perioddepends upon the water temperature and varies from 36–72 hours. At a temperature of about 28–31°C the hatching takes place in about45–50 hours.

The newly hatched out larvae are 4–5.5 mm in length with a prominent yolk sac. The newly hatched out larvae adhere to the leaves of theweeds and remain in this condition for some time. The yolk is absorbed within 2–4 days after hatching depending on the watertemperature. The weeds are removed very carefully from the hatching hapas and the spawn are removed during the early morning hours.Collected spawns are sieved through a coarse mosquito netting cloth to remove debris, measured with a seive cup and transferred tonursery ponds.

However, this early stage of fish seed is not suitable for stocking in all types of ponds. The spawn is nursed for 2 or 3 weeks up to fry stagein nursery ponds and then the fry (2–3 cm) are transferred to rearing ponds where they are reared for three more months up to fingerling(8–12 cm) stage. This is the fingerling stage of the fish seed which should be used for stocking the composite fish culture ponds.

Figure 31. Hatching Hapas in a Pond

8.2 Feed

Undrainable ponds have the ability to continuously supply natural fish food for the cultivated carp species. But the quantum of the naturalfood usually available in the pond is not sufficient to support the dense fish population cultivated under semi-intensive and/or intensive fishculture systems. As such, natural feed is always supplemented with some artificial feed to achieve optimum production. A brief account ofthe natural food available in undrainable ponds and the supplementary feed used in fish culture in undrainable ponds is presented below.

8.2.1 Natural food

Some of the cultivable fish species such as trout, salmon, eel, etc., are exclusively fed on artificial food. On the other hand, carps requirenatural food and many feel that at least 50% of the food ingested by them should be the natural food items. Hence the availability ofnatural feed is one of the major factors contributing to fish production in undrainable ponds. Natural feed, being balanced, not only providesthe essential nutrients such as proteins, carbohydrates and fats, but also takes care of the much needed vitamins and minerals to thecultured fish which may not be present at the desired levels in artificial feed unless otherwise fortified. Natural feed, in addition, possesssome of the essential amino acids and fatty acids required for growth while most of the artificial feed may be deficient.

8.2.1.1 Principal natural fish food

An undrainable pond ecosystem provides a wide variety of natural food to the fish. The following groups of organisms are important (Figs.32A and 32B).

A. Phytoplankton: Chlorophyceae - Green algae Bacillariophyceae - Diatoms Myxophyceae - Blue-green algaeB. Zooplankton: Protozoans - Sarcodines, flagellates and Ciliates Rotifers - Branchionus sp. - Asplanchna sp. - Keratella sp. - Polyarthra sp. etc. Crustacea - Cladocerans - Moina sp. Cida sp. Ceriodaphnia sp. - Copepods - Nauplii Diaptomus sp. Cyclops - Ostracods - Cypris sp. Stenocypris sp.C. Zoobenthos: In addition to some species of Cladocerans and Ostracods, the following groups are also represented. Crustacea - Macrobrachium sp. Water mites Aquatic insects - Odonatans, Hemipterans, Trichopterans, Lepidopterans, Coleopterans and Dipterans. Molluscs - Pila sp., Viviparus sp.,

Lymnaea sp. and Lamellidens sp.

In addition to these, bacterioplankton, detritus materials coated with bacteria and periphyton are also equally important as natural fish food.

The aquatic bacterial community while regulating a large number of important processes in the pond energy flow and mineral recycling,also serve as food for several carp species. The quantity of bacterioplankton depends on the primary production and the added organicmatter. In newly constructed and desilted ponds, the bacterial numbers are much less, whereas in old ponds the bacterioplanktonpopulation is found to be the highest.

Planktonic detritus particles associated with bacteria are freely suspended in the water column and they serve as food for filter feeders.

The sediment detritus constitute the food of benthophagous fish species which utilize it directly. Most of these particles originate from thedecomposing macrophyte remains.

The fauna associated with the sediment and the macrophytes have relatively longer generation time than the planktonic organisms; eventhen they occupy an important place in the natural food resources for the pond fish. The natural food produced in the pond are varied andare able to cover the entire choiced food spectrum of all the six species of carps cultured together. Carp species have their own preferencefor natural food which varies with the different stages of their life cycle (Table 12).

8.2.1.2 Availability of natural food for fish in ponds

The availability of natural food to fish in ponds depends on the quality and the quantity of the standing crop which in turn is determined bythe extent of exposure of the pond to fish culture, stocking density, species stocked, the size of the fish reared and on fertilizationprogrammes. The sources from which the nutritive fauna develops in the ponds are numerous, the main among them being the portion ofthe ponds that never dried, the water which has been used to refill the pond, the bottom soil with organisms in hibernation or their encystedstages, wind-borne encysted organisms (copepods, cladocera, rotifers, etc.), eggs laid by insects, etc. In the presence of sufficient foodand favourable environmental conditions, these fish food organisms multiply at a faster rate. Pond fertilization helps in increasing theamount of natural food in the pond through the supply of the necessary nutrients which are either lacking or are insufficient in the pondecosystem. This helps the growth of primary producers - the phytoplankton and macrophytes which form the food of fish and herbivorouszooplankters. Organic manure containing practically all necessary nutrients required for biological production, encourages bacterial growthwhich in turn favour better production of zooplankton and increases the effectiveness of many inorganic fertilizers by providing necessaryorganic matter base. Details about pond fertilization with organic manures and inorganic fertilizers are discussed in the next section of thismanual.

Table 12Natural food preferences of the Asiatic carps at different stages of their life cycle

Species Stages of life cycleLarvae Fry Fingerlings Adult

Catla (Catla catla)Protozoans, rotifersunicellular algae,etc.

Protozoans, rotifers andcrustaceans.

Crustaceans, algae, rotifers andsome vegetable debris

Crustaceans, algae, rotifers, plant matters,etc.

Rohu (Labeo rohita) - do - Protozoans, rotifers, crustaceans,unicellular algae.

Vegetable debris, phytoplanktoncrustaceans, detritus, etc.

Vegetable debris, microscopic plants,detritus and mud.

Mrigal (Cirrhinusmrigal) - do - Crustaceans, rotifers, planktonic

algae.Vegetable debris, unicellular algaedetritus and mud.

Blue-green and filamentous algae,diatoms, pieces of macrophytes, decayedvegetable matters, mud & detritus.

Grass carp(Ctenopharyngodonidella)

Protozoans, rotifers,copepod nauplii.

Protozoans, rotifers, crustaceans,microzoobenthos, detritus,microalgae, plant fragments.

Detritus and aquatic plants.Aquatic plants such as wolffia, lemna,spirodela, hydrilla, najas, ceratophyllum,chara, etc.

Silver carp(Hypophthalmichthysmolitrix)

Unicellularplanktonicorganisms, naupliiand rotifers.

Copepods, cladocerans andphytoplankton.

Falagellata, dinoflagellata,myxophyceae, bacillariophycea,etc.

Mainly phytoplankton.

Common carp(Cyprinus carpio)Var. Communis

Protozoans, rotifers,cereodaphnia,moina, nauplii, etc.

Rotifers, cyclops, cereodaphnia,moina, nauplii, euglena,oscillatoria, etc.

Diaptomus, cyclops, moina,cereodaphnia, ostracods, insectsincluding chironomid larvae.

Decayed vegetable matter, worms,molluscs, chironomids, ephemerids andtrichopterans.

Figure 32A. Natural Fish Food Organisms (Phytoplankton)

Figure 32B. Natural Fish Food Organisms (Zooplankton)

Some of the fish food organisms such as rotifers (Brachionus sp.) and cladocerans (Bosmina sp., Moina sp., Daphnia sp.) can be culturedon a mass scale in earthen enclosures, plastic pools, tanks, etc, and may be inoculated into the nursery ponds. Cow dung and oil cake areapplied initially at the rate of 250–350 ppm and 50 ppm respectively, and subsequently after every four days at the rate of half the initialdose. After the treatment, seeding is done with 2–5 ml of Moina sp., collected from nearby ponds. Moina thus cultured may be used forseeding nursery ponds at the rate of 30–50 ml of Moina/ha (Jhingran and Pullin, 1985). Chemical analysis of plankton show that on anaverage, crude protein constitutes 44% to more than 57% of the dry organic matter. Plankton has relatively small amounts of fat averagingto about 5–7%.

8.2.2 Supplementary feed

The fish production rate may be increased significantly by merely supplementing the natural food with artificial feed which can supportmore fish with increased individual weights, resulting in a more profitable operation. All the carp species including the predominentlyplankton feeders like catla and silver carp and macrophyte feeder grass carp accept supplemental feed.

8.2.2.1 Conventional feeds

The conventional supplementary feed is usually a mixture of brans and oil cakes in 1:1 ratio by weight. In India, oil cakes such as mustardoil cake or groundnut oil cake and rice or wheat bran are widely applied depending on their local availability. In Bangladesh, the mostcommon fish feed is the mixture of mustard oil cake and rice or wheat bran. In Nepal, farmers are advised to feed a mixture having maize,wheat or rice bran and mustard oil cake. In certain regions, finely chopped vegetable matter or grass are also mixed. The same feed isapplied in nursery, rearing and stocking ponds. Aquatic weeds or sometimes green animal fodder are given to grass carp. Smaller aquaticweeds such as wolffia, lemna, spirodela, etc., are provided in the early stages while large macrophytes and green animal fodder to thebigger fish.

8.2.2.2 Balanced supplementary feed

Using locally available feed materials and mixing with vitamin premix, essential minerals and trace elements, a balanced supplementaryfeed can be compounded without any significant increase in its cost which will give better results than the conventional one. However, thebackground knowledge of the nutritional requirement of carps becomes essential for formulation of suitable balanced supplementary feed.

The quantity and quality of nutrients required by carps for attaining optimum growth vary with the species, size and stages of the life cycle.Essential nutrients such as protein, fat, carbohydrate, vitamins and minerals are required as raw materials for the formation of body tissues,production of energy and also to regulate the vital physiological processes.

Protein: Protein requirements may be looked at the gross protein and specific amino acid requirement levels. Protein requirement isinfluenced by several factors like water quality, natural food availability in ponds, dietary protein quality, the amount of non-protein energyin the diet, stocking density, etc. Protein requirement levels of some carp species are given in Table 13.

Table 13Protein requirements of certain carps

Species Crude protein level in diet for optimal growth (g/kg) ReferenceCommon carp 450 – 480 Sen et al., (1978) Sin (1973)Rohu 450 Sen et al., (1978)Mrigal 450 Singh et al. (unpubl.)Grass carp 410 – 431 Dabrowski (1977)

Though dietary protein levels have been shown as optimal for fry and fingerlings of Indian major and common carps (Table 13), quality ofthe protein in terms of its amino acid composition is important or else growth would suffer even if the dietary protein level is high. Plantproteins are deficient in certain essential amino acids like methionine. Their quality can be improved by the addition of animal proteins suchas fish meal, bone meal, blood meal, etc. (Table 14).

Table 14Essential Amino Acid requirements of common carp (Cyprinus carpio)

(Adapted from National Research Council, 1983)Requirement

Amino acid % of protein % of diet Total protein in the diet (%)Arginine 4.2 1.6 38.5Histadine 2.1 0.8 38.5Isoleucine 2.3 0.9 38.5Leucine 3.4 1.3 38.5Lysine 5.7 2.2 38.5

Methionine + 3.1 1.2 38.5

Phenylalanine ++ 6.5 2.5 38.5

Threonine 3.9 1.5 38.5Tryptophan 0.8 0.3 38.5Valine 3.6 1.4 38.5

+ In the absence of cystine++ In the absence of tyrosine

Carbohydrates: Carbohydrate requirement of carp species is highly variable ranging from 10–45%. Common carp utilizes 25%carbohydrates effectively as energy source (Takeuchi, Watanabe and Ogino, 1979; Sen et al., 1978), while for mrigal fingerlings it is 28%in synthetic diets (Singh, Sinha and Kumar, (unpubl.). Although higher levels of carbohydrate may be utilized by carps, diets containingover 40% dextrin results in retarded growth and lowered feed efficiency due to lower digestibility. The most likely symptom of over supplyof carbohydrates in diet is excessive deposition of fat in the liver and carcass. However, the protein requirements of carps can be broughtdown to some extent by raising the level of dietary carbohydrates.

Lipids: The polyunsaturated fatty acids (PUFA) is considered to be the most important class of lipids as far as lipids are concerned. Carpscan derive their lipid requirement from natural feed available in the pond since these compounds are readily available in planktonic andother biotic communities. Lipids are also considered to be the most important sparing compounds. By adding 5% of soyabean oil theoptimum protein requirement of young mirror carp can be brought down to 33% from 38%. The addition increases the dietary metabolizedenergy from 2.8 to 3.1 Kcal/g.

Vitamins: Studies on vitamin requirements of fish are very limited. The values of quantitative requirements of vitamins in common carpand the symptoms of their major deficiencies are presented in Table 15.

Table 15Dietary vitamin requirements of the common carp

(Cyprinus carpio) and related deficiency symptoms(From National Research Council, 1983 and other sources)

Vitamin Requirement (mg/kg diet) Major vitamin deficiencysymptoms

Thiamin Na Nervousness and fading of body colour.Riboflavin 7.0 Hemorrhages on skin, fin, mortalityPyridoxine 5–6 Nervous disordersPantothenic acid 30–50 Poor growth, anaemia, skin hemorrhages, exophthalmiaNidcotinic acid 28 Hemorrhages on skin, mortalityBiotin 1 Poor growthFolic acid N None detectedVitamin B12 N None detected

Choline 4 000 Fatty liverInositol 440 Skin lesionsAscorbic acid Na Impaired collagen formationVitamin A 10 000 IU Faded colour, exophthalmia, hemorrhages on fin and skinVitamin D N None detectedVitamin E 200–300 Muscular dystrophy, mortalityVitamin K N None detected

N = No dietary requirement demonstrated under variousenvironmental condition.Na = Not available

Minerals and trace elements: Like higher vertebrates, carps also have dietary requirements of minerals such as calcium, iron,magnesium and phosphorus and trace elements such as cobalt, iodine, zinc, copper, manganese, sulpher, fluorine, molybdenum, etc. Forcommon carp the minimum requirement of phosphorus in the diet is 0.6–0.7% and that of calcium is about 0.028%. 1% dicalcium-phosphate is recommended in the feed for adult fish in polyculture system in ponds. Trace elements are growth stimulants and arerequired in traces. Sen and Chatterjee (1976, 1979) reported that cobalt chloride and manganese at the rate of 0.01 mg/day/fish giveshigher rates of survival and growth of spawn, fry and fingerlings of Indian major carps. Rohu requires about 0.014% dry diet of iron. Ingeneral, carps appear to be less sensitive to mineral deficient diets than other fish possibly due to meeting their dietary mineralrequirements from natural sources under pond culture condition.

Common feedstuffs: A large number of feed stuffs are presently being used as supplementary feed for carps in undrainable pondculture systems. Some of them are widely available and extensively used. These may be broadly classified into two groups: the feeds ofplant origin and the feedstuffs of animal origin.

Cakes of oil seeds such as groundnut, mustard, linseed, coconut, etc., are a most useful and widely used feedstuff of plant origin with highfat and protein contents. Brans of rice, wheat and other grains are equally popular and used in combination with oil cakes. Such meal assoya waste after oil extraction is excellent feed for carps. Broken cereals such as rice, wheat, maize, etc., are good but expensive feedmaterials. Leafy feeds are suitable for grass carp. Tender leaves of various aquatic and terrestrial plants (cassava, maioc, colocasia,banana, sweet potatoes, maize, etc.) and green animal fodder such as berseem, napier, paranapier, elephant grass, etc., are also used.Miscellaneous items such as kitchen wastes, household scraps, residues of bakery, beer brewing or rice-wine industry wastes can beprofitably used as fish feed.

Dried fish meal (fish flour) is the most common and cheapest source of animal protein and widely used in livestock and fish feeds.Slaughterhouse offals, prawn head meal, bone meal, silkworm pupae and items like snails, oligochaete worms, etc., are also widely useddepending on their availability and price. Nutritive values of some commonly used feedstuffs are presented in Table 16.

Digestibility and absorption greatly vary with the quality of the feedstuffs and also from fish to fish. The values of total digestible nutrients incommon feedstuffs are given in Table 17.

Table 16

Proximate composition of some of the common fish feed stuff(Adopted from ADCP. (1983))

As percentage of dry matter

Common name DM CP EE CF Ash NFE Ca P Methioine & czstine Lysine Digestible energy

K cal/kgA. Plant product Groundnut oil cake 94.0 40.1 12.2 14.0 7.8 25.9 - - 0.52 1.44 3 018 Groundnut oil meal 89.7 37.3 0.3 6.2 3.0 35.7 0.22 0.75 0.48 1.34 2 155 Coconut oil cake 92.3 18.1 8.9 16.4 4.6 52.0 0.21 0.58 0.34 0.45 2 960 Soyabean cake 84.8 47.5 6.4 5.1 6.4 34.6 0.13 0.69 1.42 2.90 3 009 Soyabean oil meal 88.7 52.8 1.5 6.6 7.6 46.7 - - 1.58 3.22 3 060 Cotton seed oil cake 87.9 26.4 5.7 24.2 6.6 37.1 - - 0.74 1.08 2 572 Sunflower oil cake 91.0 34.2 14.3 13.2 6.6 31.8 0.30 1.30 1.36 1.19 3 394 Sunflower oil meal 90.0 42.7 4.0 16.1 7.7 29.5 - - 1.70 1.49 2 827 Linseed oil cake - 30.5 6.6 9.5 10.2 43.2 0.37 0.96 1.34 1.07 2 983 Sesame oil cake 90.0 32.2 14.4 20.3 11.1 22.0 - - 1.64 0.93 3 035 Ground maize 89.6 5.1 8.7 3.9 1.1 81.2 - - 0.10 0.12 3 326 Wheat bran 90.7 13.9 8.3 13.1 4.6 60.1 - - 0.42 0.53 2 995 Rice bran 91.3 13.7 5.4 20.0 18.1 48.8 - - 0.52 0.56 2 416 Rice polish 91.6 12.4 16.7 12.0 14.1 44.9 - - 0.73 0.78 3 154 Millet 88.4 12.0 4.8 11.3 5.0 66.9 0.57 3.21 0.36 0.43 2 847 Black gram bran 88.8 7.0 3.6 24.0 8.9 56.5 - - 0.12 0.51 1 684B. Animal products Blood meal 89.5 88.5 1.2 0.4 6.0 3.9 0.28 0.28 1.95 7.08 3 576 Bone meal 75.0 36.0 4.0 3.0 49.0 8.0 22.0 10.0 0.25 1.69 2 000 Fish meal 86.0 55.6 12.0 2.9 21.3 8.2 - - - - 3 569 Prawn meal 89.4 31.2 11.7 17.6 39.5 0.0 - - - - - Silk worm pupae 20.0 54.2 30.3 3.9 5.2 6.4 0.1 1.1 - - 4 910 Fresh cattle manure 17.9 8.4 3.1 22.5 18.8 47.2 - - - - 1 983

DM - Dry matter;CP - Crude protein;EE - Ether extract;CF - Crude fibre;

NFE - Nitrogen free extract;CA - Calcium;P - Total phosphorus.

Usually the crude protein level of the supplementary feed is fixed at about 5 to 10% below the dietry protein requirement of the fish to befed. Vitamins, minerals and trace elements are added as required.

Table 17Values of digestible nutrients in carps for some common feedstuffs

Feedstuff Digestible nutrients (%)Coconut oil cake 67.5 – 69.8Ground nuts 79.3Rice bran 79.4Maize (Corn) 77.9Maize (fresh) 74.9 – 75.1Rye 75.9Sweet potato 25.8Radish leaves 8.2Fresh silkworm pupae 34.3

Formulation of feed: Easy availability, low cost, high digestibility and high nutrient contents are the major considerations in selectingthe fish feed ingredients for feed formulation. Feed constitute the major operating cost in undrainable pond fish culture and therefore, ourultimate objective is to supply essential nutrients at the minimum possible cost. Formulated feeds may be either a complete feed withoptimum level of all the essential nutrients and energy to provide complete nutrition or a supplementary feed - a diet basically tosupplement energy and a portion of protein and other essential nutrients. In undrainable pond culture systems where natural feed aremade available by pond fertilization, feed is required only to supplement the natural feed. The initial step involves surveying market pricesof the locally available feedstuffs and tabulation of data as mentioned below as an example (Table 18).

Table 18Data tabulation example for selection of feedstuff

Feedstuff Market price(US $/kg)

Proteincontent

Cost/kgprotein

Grade forselection

(US $)Groundnut oil cake 0.15 38.2 0.39 IIMustard oil cake 0.21 40 0.52 IIISesame oil cake 0.11 32.2 0.34 I

Thus, out of the three listed above one can easily select the feedstuff most suitable for his operation. Similar methods may be adopted tofind the best possible feed for the supply of specific major nutrients. Their amino acid profile is also to be considered for such selection.Using the locally available feedstuff, a diet with desired level of protein can easily be formulated by using the square method. The samemethod is also used for adjusting energy levels in a feed.

The required protein level of 30%, for example, is put in the centre of the square. The two selected feedstuffs with their percentage ofprotein content are put on the left hand corners of the square as shown below.

Sesame oil cake(Protein 32.3%) 30—10 = 20Desired feed protein level(30%)

Rice bran(Protein 10%) 32.2—30 = 2.3Total 22.3

The value of desired protein level of the proposed feed is substracted from each of the feedstuffs in turn and the results are placed at theopposite corner ignoring the resultant positive or negative signs. The two resultant figures on the right hand side of the square are thenadded together (20 + 2.3 = 22.3). Now to obtain 30% crude protein level in the proposed feed, the following formula is followed.

Thus, to obtain 30% crude protein level in 100 kg of feed we need 89.6 kg of sesame seed cake and 10.3 kg of rice bran to be mixedtogether. The same method can also be used to obtain a desired dietary energy level. It has been experienced that if the minimum dietaryrequirements for amino acid like arginine, lysine, methionine and tryptophan are met, the requirements of 6 other essential amino acidsusually also get satisfied. Vitamins, minerals and trace elements are added in feed according to the requirements of the species of carpsunder culture.

Pelletization: Considerable wastage is expected when supplementary feed mixtures rapidly separate into their component ingredientsduring the feeding process. However, by pelletization of supplementary feed mixture, such wastage can be minimised and furtherimprovement in the feed efficiency can be achieved. Feed in pellet forms are more readily acceptable and give better results in comparisonwith dust feed (Kumar et al., 1984). During pelletization, the soft and dusty feed is converted into hard, water-stable pellets by the processof heating and compression. Even in undrainable ponds use of supplementary feed in pelleted form promise increased production throughincreased efficiency and minimum wastage (Figs. 33A and 33B).

Figure 33A. Fish Feed in Dough Form

Figure 33B. Fish Feed in Pelleted Form

A generalised but practical account of nutrient specifications of commercial warm water aquaculture feed is given in Table 19a.

Table 19aNutrients specifications of commercial aquaculture feeds

(Warm water omnivorous species)(Adapted from ADCP, 1983)

Nutrients Fry and fingerlings Juveniles and adults Brood FishProtein (% min) 30 25 30Lipids (% min) 8 5 5Ca (% min) 0.8 0.5 0.8Ca (% max) 1.5 1.8 1.5P (% min) 0.6 0.5 0.6P (% max) 1.0 1.0 1.0Lysine (% min) 2.0 1.6 1.8DigestibleEnergy (KcaL/100 g min) 310 280 280Vitamins (Supplement), (per 100 kg)A (i.u.) 600 000 500 000 600 000D (i.u.) 100 000 100 000 100 000E (i.u.) 6 000 5 000 6 000K (g) 1.2 1.0 1.0C (g) 24.0 20.0 24.0Thiamine (g) 2.4 2.0 2.4Riboflavin (g) 2.4 2.0 2.4Pantothenic acid (g) 6.0 5.0 6.0Niacin (g) 12.0 10.0 12.0Pyridoxine (g) 2.4 2.0 2.4

Biotin (g) 0.024 0.020 0.024Folic Acid (g) 0.6 0.5 0.6Choline (g) 54.0 50.0 54.0B-12 (mg) 2.4 2.0 2.4Minerals (Supplement), (per 100 kg feed)Iron (g) 5.0 5.0 5.0Copper (g) 0.3 0.3 0.3Manganese (g) 2.0 2.0 2.0Zinc (g) 3.0 3.0 3.0Iodine (mg) 10.0 10.0 10.0Cobalt (mg) 1.0 1.0 1.0Selenium (mg) 10.0 10.0 10.0

Based upon the nutrient specifications, a number of test diets for carp fry, fingerling and brood fish are under extensive trials to determinewhich would be the preferred formulations in terms of efficiency and cost.

The conventional rice-bran and oil cake mixture lacks animal protein, minerals and vitamins and rapidly separates into its componentingredients during the feeding process. Considerable improvement is possible if this conventional rice-bran and oil cake mixture is simplyfortified with 15–25% fish meal, 0.1% mineral mixture, 0.1% vitamin mixture and pelletized. Although mineral and vitamin mixtures arecommercially available as common additive of animal feed, fish meal at a reasonable price may not be easily available in rural areas.

8.3 Fertilizers

Considerable quantities of nutrient elements are regularly removed from the pond ecosystem through the harvested fish crops and thus forretaining the pond fertility, the required amount of nutrients need to be replenished. These nutrients are broadly divided into two groups.The first group of nutrients are nitrogen, phosphorus, potassium, carbon and calcium, while the second group of nutrients which areneeded in very minute quantities constitute mainly copper, zinc, iron, manganese, cobalt, boron, molybdenum, etc. It is the first group ofnutrients which are more concerned with pond fertility in terms of primary production, consumed in more quantity and thus need to becompensated from outside in the form of fertilizers. In other words, the main objective of adding fertilizers in fish ponds is to maintain asustained production of natural fish food during the entire culture period. Fertilizers are also classified into two categories: inorganicfertilizers or mineral fertilizers and organic fertilizers or manures of plant and animal origin.

8.3.1 Organic manures

Organic manures have been in use in fish culture in India and the Far East countries for a long time. They are available in a variety offorms such as dung of cattle, sheep, pig and goat, poultry droppings; de-oiled cakes of mahua, mustard, castor, linseed, neem, etc. Theyalso come in the form of farmyard manure, compost, green manures, sewage, etc. Of these, cow dung is the most widely used manure inundrainable pond culture system. Most of the organic manures are by-products of local agriculture, animal husbandry and village basedagro-industrial activities and hence their procurement is relatively easy at low cost. They are composite in nature and provide practically allthe nutrients, including organic carbon, required for biological production. Several organic manures are immediately assimilated by theaquatic fauna and especially by the zooplankton or even by some species of cultured carps. By improving the quality of the pond bottommud they encourage bacterial growth which in turn favours better production of zooplankton and also through inducing increased bacterialdecomposition help in releasing mineral constituents of the soil into the water. It also increases the effectiveness of many inorganicfertilizers by providing the necessary organic matter base. Though the presence of the major nutrient elements in these manures is ratherat a lower level and often vary quantitatively, their effect is sustained over a longer period. However, they are required in large quantities,thereby making the procurement, transport and application somewhat troublesome and costly though the manure itself is cheap. Also,unless proper care is exercised in its use, depletion of dissolved oxygen, in the pond water is likely to occur with consequent loss of fish byasphyxiation. However, better yields of fish are obtained through a judicious manuring schedule.

8.3.2 Inorganic fertilizers

Commercially produced inorganic compounds containing major nutrients - nitrogen, phosphorus and potassium are known as inorganic orchemical fertilizers. They contain a high and fixed percentage of one or more major nutrients depending on the class (nitrogenous,phosphatic, potassic or mixed) of fertilizer. Due to their high solubility in water, the nutrients become readily available soon after theirapplication. Some fertilizers are also available in liquid form which offer several advantages over the conventional granular or powderedform of fertilizers.

8.3.2.1 Nitrogenous fertilizers

Nitrogenous fertilizers usually contain nitrogen as the principal element and are commercially available as ammonium sulphate, ammoniumnitrate, urea, etc. Most of the nitrogenous fertilizers deplete reserves of bases and make soil acid. Therefore, the form of nitrogenousfertilizers may be selected on the basis of acidity, neutrality or alkalinity of the soil type (Saha, 1969). Nitrogenous fertilizers are particularlyessential for newly constructed ponds which are poor in nitrogen and do not have sufficient organic matter in its bottom, whereas olderponds having a good layer of colloidal mud are capable of producing nitrogen by itself. Further, the efficacy of nitrogenous fertilizers isinhibited by phosphorous deficit. It is best to maintain the P/N ratio at 1/4.

8.3.2.2 Phosphatic fertilizers

Phosphatic fertilizers are by far the most effective and favourable for fish culture. It is all the more important because almost all fish pondsexhibit phosphorus deficiency. The most commonly used phosphatic fertilizers are the orthophosphates and are grouped roughly accordingto their solubility in water. Superphosphates are the most soluble in water, dicalcium phosphate is partially soluble and rock phosphorus isalmost insoluble in water. Amongst the phosphatic fertilizers, single superphosphate is extensively used and is easily available. The moreconcentrated triple superphosphate is also in use which has P2O5 (Phosphorus pentaoxide) equivalent up to 45% with 85% solubility andthus involved relatively lower transport cost. Generally, the phosphatic fertilizers are held in soil and liberated gradually with the result thatits action is extended to subsequent years of its application, mostly depending on the nature of the pond bottom.

8.3.2.3 Potassic fertilizers

Although potassium ranks as a major nutrient like nitrogen and phosphorus, its importance in pond fertilization is less pronounced since itis available in a required quantity in natural waters. Muriate of potash (Kcl) and sulphate of potash (K2SO4) are the two commonly usedfertilizers as a source of potassium. The favourable action of potassic fertilizers can be seen in ponds with low alkalinity, with peatybottoms. In general, for ponds in which phytoplankton production is rather slow, potassic fertilizers may be tried. It also improves thehygienic conditions of fish ponds, particularly the rearing ponds.

8.3.2.4 Calcium

Though calcium is not considered as a nutrient to be used as fertilizer, it is another integral part of the ecosystem and is usually applied toget the benefit of added fertilizers used in a pond. In ponds where the water is poor in calcium (less than 8 mg Cao/1), the freshwater flora,molluscs and crustaceans are either rare or absent which in turn diminishes the nutritive value of the water. Calcium present in requiredquantities also neutralises the harmful action of excessive magnesium, sodium and potassium salts. It is usually applied in the form of lime,which is widely available as ground lime stone (CaCo3), slaked lime (Ca(OH)2) and quick lime (Cao). Composition of some importantmanures and inorganic fertilizers commonly used in pond culture are listed in Table 19b.

Procurement of organic and inorganic fertilizers is relatively easier than other essential inputs like feed and seed. Organic manures arelocally available and in most cases they are available within the community. However, due to extensive adoption of intensive crop farmingthere is a growing demand for animal manure or compost in agriculture. Instead of procuring the whole lot of required manures at a timeand storing them for application over extended periods, it is always convenient and desirable to procure materials in small quantities andapply them as and when required. While storing the manure, it should be covered to protect it from direct sunlight. Inorganic fertilizersbeing extensively used as an agricultural input, the listed fertilizers (Table 19b) are easily available in the local markets. Prolonged storage,high humidity, etc., cause deterioration in the quality of inorganic fertilizers and hence only a specified quantity of materials required for 2-3months should be procured at a time. Selection of fertilizers depends mainly on their nutrient content, cost and suitability for the specificsoil condition.

Table 19bNutrient profile of some common manures and

fertilizers used in pond fertilization

Items

Nutrient content (%)

Nitrogen(N)

Phosphate asPhosphoric(acid(P205)

Potassium asPodtash (K20)

Fresh excreta of animals: Cow 0.60 0.16 0.45 Sheep 0.95 0.35 1.00 Pig 0.60 0.45 0.50 Duck 1.00 1.40 0.62 Hen 1.60 1.5 – 2.00 0.8 – 0.9Deoiled cakes: Mustard 4.5 2.0 1.0 Groundnut 7.8 1.5 1.3 Mohua 2.5 0.8 1.8Others: Farmyard manure 0.5 – 1.5 0.4 – 0.8 0.5 – 1.9 Compost 0.4 – 0.8 0.3 – 0.6 0.7 – 1.0 Green manure 0.5 – 0.7 0.1 – 0.2 0.4 – 0.8Inorganic fertilizers: Nitrogenous - Ammonium sulphate 20.5 - - Urea 43–45 - - Ammonium nitrate 20.5 - - Sodium nitrate 16.0 - -Phosphate: Single superphosphate - 16.0–20.0 - Triple superphosphate - 40.0–45.0 -Potassic: Muriate of potash - - 48.0–62.0 Sulphate of potash - - 47.0–50.0



More details

9. POND MANAGEMENTCarp culture in ponds is basically a three-tier culture system where the first step begins with the rearing of spawn up to fry (2–3 cm) stage for 2–3 weeks in nursery pondsfollowed by rearing of 2–3 weeks old fry for about 3 months up to fingerling stage (8–12 cm) in rearing ponds before they are finally released in stocking ponds for growingup to table size fish. To ensure high rate of survival and growth during all the three stages of rearing, a package of management practices should be strictly followed, andslackness at any stage of the management procedure may affect farm productivity and profitability adversely. Techniques of management involve (i) manipulation of pondecology to ensure optimum production of natural fish food while maintaining the water quality parameters within tolerance limits of the stocked fish species; and (ii) thehusbandry of fish through stock manipulation, supplementary feeding and health care. Broadly, the various steps involved in the management of ponds at all the threestages of culture may be classified as (i) pre-stocking, (ii) stocking and (iii) post-stocking management operations.

9.1 Pre-stocking management

Pre-stocking management aims at proper preparation of ponds to remove the causes of poor survival, unsatisfactory growth, etc., and also to ensure ready availability ofnatural food in sufficient quantity and quality for the spawn/ fry/fingerlings to be stocked. Pre-stocking part of the management involves the following sequential measures.

9.1.1 Eradication and control of aquatic weeds and algae

Aquatic weeds are unwanted plants that grow within the water body and along the margins. Unlike in temperate climate, the pond fish culture in tropics face seriousproblems due to weed infestation and frequent appearance of algal blooms. They remove a large quantity of nutrients from the water, which otherwise would go into theproduction of planktonic growth. Even the poor fish crop that is produced in weed chocked water is difficult to harvest. The fishes are subjected to stress due to dissolvedoxygen depletion and wide fluctuation between the dissolved oxygen values of the day and night. Decomposition of the dead aquatic weeds further creates the oxygenproblem. Dense growth of the submerged weeds restrict fish movement and interfere with fishing operations. Filamentous algae often get entangled in the gills of the fishand suffocate them to death. Floating weeds such as water hyacinth, pistia, etc., very often cover the entire water surface cutting off light drastically, thus resulting incritical reduction in primary productivity of the pond. Common aquatic weeds creating problems in fish culture ponds (Fig. 34) are broadly classified according to theirnature of occurrence, into four major groups. They are floating, emergent, submerged and marginal. In addition, algal blooms and mats also create serious problems interms of dissolved oxygen and production of certain toxic materials in some cases. Aquatic weeds of common occurrence in undrainable ponds are grouped in thefollowing Table (Table 20).

Figure 34. Common Aquatic Weeds in Underainable Ponds

Table 20Groups of commonly occurring aquatic weeds,

algal bloom and algal mats in undrainable ponds

Aquatic weeds, algal bloom and algal matsGroups Scientific name Common name

Floating

Eichhornia crassipes Water hyacinthPistia stratiotes Water lettuceSalvinia cucullata Water fernSpirodela polyrrhiza Duck weedLemna minor Duck weed

Emergent Nymphea mexicana Banana water lilyNymphea tuberosa Fragrant water lilyNelumbo spp. LotusNymphoides spp. Floating heart

Submerged Hydrilla verticillata HydrillaNajas marina/minor NajasPotamogeton crispus Curly leaf pondweed

http://www.fao.org/



Vallisneria spiralis Eel grassOttelia spp.

Marginal Ipomea aquatica IpomeaJussiaea spp. Water primroseTypha anqustata Cat-tailsCyperus spp. Cyperus

Algal blooms Microcystis aeruqinosa MicrocystisAnabaena Blue green algae

Algal mats Pithophora Horse hair clumpSpiroqyra Filamentous algae

Control measures for all the above mentioned classes of weeds and blooms fall into four major categories, viz. preventive, manual and mechanical, chemical andbiological. Any of these methods or at times a combination of methods may be taken up depending on the nature of infestation, pond condition, cost involvement andavailability of required inputs.

9.1.1.1 Preventive control

Taking into consideration the high cost of controlling aquatic weeds, certain preventive measures are to be followed to reduce the chances of their infestation.

The preventive measures have to be taken well in advance. The measures include trimming of pond margins, dewatering and desilting of old ponds, uprooting or burningof dried marginal weeds during the summer and providing barriers to prevent the entry of floating weeds.

9.1.1.2 Manual and mechanical control

Manual removal of aquatic weeds is an age-old practice and holds good even today in rural areas. The free floating groups of weeds are either hand picked or dragged bywire or strong coir rope nets. In bigger ponds they should be removed part by part from the marginal areas and finally the centrally located weed mass is dragged towardsthe banks and lifted out. Certain small and light floating weeds such as spirodela, lemna, azolla, wolffia, etc., are easily skimmed out by twisted straw ropes or finemeshed nets. The manual removal of submerged weeds from a heavily infested water body is relatively much more difficult. They are either pulled by hand or hand-drawnbottom rakes or uprooted with bamboo poles having a cross piece tied strongly at the terminal end. Repeated cutting of the aerial shoots and leaves of rooted emergentplants are also useful. Implements used for manual control are mostly hand scythes for cutting, and hand forks, strong nets and bamboo poles with terminal cross piecefor twisting and uprooting (Fig. 35).

Mechanical devices used for clearance of rooted submerged weeds are steel cables, cutting chains and diesel operated winches (Mitra, 1956).

9.1.1.3 Chemical control

The manual removal of weeds from heavily infested large water bodies is difficult and time consuming. Under such conditions certain commercially available chemicals(herbicides) can provide an efficient means of eradication of undesirable aquatic plants. Total kill and disintegration of weeds can be achieved by this method ensuring fullreturn of the nutrients back to pond soil and water for production of natural fish food. As a matter of fact there is not a single chemical known so far which can eradicate alltypes of weed infestation. Therefore, one must know the weeds and its species, appropriate herbicide and its rate and time of treatment. In larger ponds where denseinfestation covers a substantial portion of the water, the herbicide should be applied part by part if the pond is already stocked with fish. As discussed earlier mostherbicides are selective in nature and when applied to a mixed population of weeds, growth of some tolerant weeds may be encouraged at the cost of susceptible ones;likewise, when surface or floating weeds are destroyed, the submerged weeds develop. Under such conditions subsequent application of appropriate herbicide should betaken up.

Floating weeds: Water hyacinth is one of the most important weeds of this group. Depending on its degree of infestation, they are categorized in three groups, viz.small, medium and big, based on their wet weight per unit area. The recommended doses of the herbicide 2–4-D are 2,7 and 12 kg/ha for small (13 kg/m2), medium (23kg/m2) and big (35 kg/m2) (Ramchandran, 1969; Patnaik and Das, 1983). Addition of a detergent (0.2 % concentration) to the aqueous solution gives better results. Thedilution for better coverage has been estimated at 400 l/ha. The foliar spray (spraying over the leaves) is undertaken with the help of a foot pump/hand pump sprayer witha three-action nozzle. Field application of herbicide, especially towards the interior of thick water hyacinth infestation, is a difficult task. In such cases a pair of stoutbamboo poles should be laid on the top of the infestations so that the operators can walk over them. Normally, the complete kill of plants takes around 25 days. Thischemical is available in two suitable forms as sodium and amine salt.

Figure 35. Hand tools Used for Manual Control of Aquatic Weeds

Water lettuce which often causes a serious problem in fish ponds can be controlled with 0.1–0.2 kg of paraquat/ha. This infestation could also be controlled by foliar sprayof aquous ammonia (1%) at the rate of 50–75 kg/ha along with 0.2 % of any commercially available detergent as a wetting agent.

The aquous ammonia is broadcast as foliar spray over the infestation with a foot pump sprayer and a small funnel–shaped sprinkler 3–4 cm in diameter, provided with 10pin-sized holes pierced on the diaphragm covering the mouth of the funnel. The stem of the sprinkler is connected to the sprayer through a 30 m long polyethene tube, sothat the sprayer is kept on the shore and only the sprinkler is taken inside the infested area in a boat.

The area to be treated inthe field is divided into small plots (20–30 m2size) and solution is sprayed at the rate of 5 000 1/ha.

Salvinia forms a thick surface mat in ponds and can be conveniently controlled by the application of foliar spray of paraquat at the rate of 1 kg/ha. Usually it takes 30–40days for the weeds to be killed and settled in the pond.

Smaller floating weeds, e.g. Spirodela, Lemna and Azolla can also be cleared with 0.1 kg/ha of paraquat.

Emergent weeds: Water lily, lotus, and floating heart can be cleared by spraying the herbicide 2–4-D at the rate of 8–10 kg/ha with detergent (0.25%). The chemical isdiluted at the rate of 300 l/ha and sprayed through a footpump sprayer.

Submerged weeds: Ottelia, Vallisneria, Hydrilla, Najas, Potamogeton and Ceratophyllum can be controlled by paraquat at the rate of 3–4 ppm within two weeks. Itcan also be controlled by application of anhydrous ammonia at the rate of 15–20 ppm.

Marginal weeds: Ipomea, Jussiaea, etc., could be controlled by spraying the herbicide 2–4-D at the rate of 8 kg/ha.

Algal blooms and mats: Due to overdose of fertilizers or enrichment of the water through treated sewage or agricultural fertilizer, the minute algal cells multiply fastturning the pond water bright green or sometimes brickred. Some of the more harmful blooming algae are microcystis, anabaena and euglena. A number of chemicalshave been employed to control these algal blooms. Copper sulphate is perhaps the oldest and a very widely used algicide. The recommended doses are 0.2 to 1.0 ppm,but it is not very effective in ponds having high pH (pH above 8.6), Microcystis bloom is cleared with 0.3 to 0.5 ppm of Diuron. Simazine also clears the bloom in 16–20days and the rate of application is 0.3–0.5 ppm. Both the chemicals do not have harmful effect on fish. It has been observed that the sudden kill of blooms is likely tocause oxygen depletion which might cause mortality of fish. In order to avoid this a prophylactic dose of diuron (0.1 ppm) should be applied in the very early stage ofbloom development. Usually the chemical is sprayed over the affected portions of the ponds. The common mat forming algae which occur in fish ponds are Spirogyra,Pithophora, Oedogonium and Cladophora. Although repeated netting can reduce the infestation to a considerable extent in nursery and rearing ponds, application ofDiuron at the rate of 0.3–0.5 ppm is recommended. Various chemicals and the dose of application is summerised in the ready reckoner given below (Table 21).

9.1.1.4 Biological control of aquatic weeds

Another important controlling method is by introduction of weed-eating fishes. Common carp, gourami, tilapia, pearl spot, the grass carp and a species of puntius are thefishes of known weed-eating habits (Table 22).

Grass carp is the most effective biological control agent against most of the submerged and floating weeds except the water ferns. Grass carp normally consumes choicedaquatic weeds, at least 50% of their body weight in a day. About 300–400 fish, each of about 0.5 kg weight, are enough to clear 1 ha of Hydrilla infested water body inabout a month. Normally Hydrilla infestation density ranges from 5–25 kg/m2 (Alikunhi and Sukumaran, 1964).

9.1.2 Eradication of unwanted fish

Predatory fish prey upon the spawn, fry and fingerlings of carps and the weed fish compete with carp for food, space and oxygen. Therefore predatory and weed fishshould be completely eradicated from nursery, rearing and stocking ponds before these ponds are stocked. The commonly encountered predatory and weed fish inundrainable ponds are listed below (Table 23).

Absolute removal of these unwanted fish by thorough and repeated netting is not possible and hence dewatering and poisoning the pond are the only alternative methods.If situation permits, dewatering should be the preference as it ensures complete eradication of unwanted fishes and disinfects the pond bottom. Dewatering also offers theopportunity to desilt the pond bottom. However, where it is not possible, which is true in most situations, the pond should be treated with fish poison. From an economicpoint of view the poisoning should be done during pre-monsoon season when the water level is usually low, requiring the minimum quantity of poison material. The date ofpoisoning, however, should be fixed about three weeks before the anticipated date of stocking. Seasonal ponds which dry up during summer months need not be treatedwith fish toxicants.

Table 21Ready reckoner for chemical control of aquatic weeds

Weeds Herbicide Brand name Dose Additives

1. Water hyacinth pistia and other floating weed 2–4–D (sodium salt/aminesalt)

Taficide HexamarFernoxone 2–12 kg/ha 0.1–0.2%

detergents2. Lotus, water lily trapa, etc. -do- -do- 8–10 kg/ha 0.25% detergent3. Marginal weeds -do- -do- 8 kg/ha 0.25% detergent4. Salvinia Paraquat Gramoxone 1.0 kg/ha -5. Pistia,spirodela lemna, azolla, etc. -do- -do- 0.1–0.2 kg/ha 0.1% detergent

6. Submerged weeds (Ottelia, vallisneria, hydrilla, najas, potamogeton,ceretophyllum, etc.) -do- -do- 4 ppm -

7. Pistia Aquous ammonia Dry ammonia gas 50–70 kg/ha 0.2% detergent8. Submerged weeds Anhydrous ammonia Dry amomia gas 15–20 ppm -9. Rooted submerged weeds Copper sulphate - 35 kg/ha -

10. Algal blooms/mats Copper sulphate – 0.2–1.0 ppm (not very affective athigh pH -

Simazine - 0.3–0.5 ppm -Diuron Karmex 0.3–0.5 ppm –

Table 22 Common weed eating fish and the weeds of their preferenceFishes Names Feed upon

Common carp Cyprinus carpio Tender shootsGaurami Osphronemus goramy Tender shoots of submerged weeds and filamentous algaePearl spot Etroplus suratensis Filamentous algaeGrass carp Ctenopharyngodon idella Submerged weeds e.g Hydrilla Najas, Ceratophyllum, Potamogeton, Ottelia and duck weedsSilver carp Hypophthalmichthys molitrix Algal bloom

Table 23Common predatory and weed fish of undrainable ponds

Predatory fish Weed fishChanna spp. Puntius spp.Clarias batrachus Oxygaster spp.Heteropneustes fossilis Gudusia chapraPangasius pangasius Amblypharyngodon molaMystus spp. Laubuca spp.Ompok spp. Esomus danricusWallago attu Osteobrama cotioGlossogobius giurisMastocembelus spp.Amphipnous cuchia

9.1.2.1 Fish toxicants

Although a number of chemicals and plant derivatives are available in the market which are poisonous for fish, only a limited number of such toxicants are safe andsuitable for fish culture purposes. Based upon the following criteria a suitable fish poison is selected.

Poisoned fish should be safe for human consumption

Least adverse effect on the pond biota

Toxicity period should be of short duration

Should not have residual effect

Easy commercial availability

Simplicity of application

Cost considerations.

Mohua oil cake, bleachng powder and ammonia are considered suitable.

9.1.2.2 Application of toxicants in ponds

Mohua oilcake: Of all the fish poisons of plant origin, the most extensively used fish toxicant in undrainable ponds is oil cake of Mohua (Basia latifolia). It kills all the fishspecies within a few hours when applied at the rate of 250 ppm (CIFRI, 1968). It contains about 4–6% of active ingredient, the saponia, which on dissolving in waterhaemolyses the red blood cells and thus kills the fish (Bhatia, 1970). The required quantity of mohua oilcake should be soaked in water and uniformly broadcast over theentire pond surface. Following this operation, repeated netting should be done to ensure proper mixing of the poison and removing the affected fishes which are suitablefor human consumption. The toxicity of doses up to 250 ppm lasts for about 96 hours (Jhingran and Pullin, 1985) and subsequently it serves as organic manure in thepond. It should be applied at least two weeks before stocking the ponds.

Bleaching powder: Bleaching powder or Calcium hypochlorite (CaOCl2) is another practical and safe fish toxicant. It kills all the predatory and weed fish of the pondwhen applied at the rate of 25–30 ppm (Tripathy et al., 1980). However, during storage, significant chlorine content is lost and hence it is always safer to use thecommercially available bleaching powder at the rate of 35–50 ppm or 350–500 kg/ha/m of water. Fish kill occurs within 1–3 hours and the toxicity lasts for 3–5 days.Plankton and benthic fauna start developing from the 7th or 8th day after treatment. Chlorine content of the bleaching powder thoroughly disinfects the pond which isessential in undrainable ponds where disinfection by sun drying is not at all possible. Disinfection of the pond is one of the essential measures for maintaining properhealth condition of the fish. Besides, it also satisfies the lime requirement of the pond soil.

The method of application is also relatively simple. The powder is mixed with water and uniformly spread over the entire water surface. Distressed and dead fish areremoved by netting. Chlorine killed fish are safe for human consumption.

Ammonia: Anhydrous ammonia when applied at the rate of 20–25 ppm kills the predatory and weed fishes. Besides, it also controls the aquatic weeds and later acts asnitrogenous fertilizer. Toxicity of ammonia lasts for 4–6 weeks.

Details of doses for commonly used fish toxicants are summerised in the following table (Table 24).

Table 24Recommended doses of fish poison

Poison Dose (kg/ha/m)Bleaching powder 350 – 500Mohua oil cake 2 500Anhydrous ammonia 20 – 30Powdered seed of Croton tiqlium 30 – 50Root powder of Milletia pachycarpa 40 – 50Seed powder of Milletia piecidia 40 – 50Seed powder of Barrinqtonia acutanqula 150Seed meal of tamarind (Tamarindus indica) 1 750 –2 000

Tea seed cake (Camellia sinensis)* 750

* Requires additional dose of lime at the rate of 150 kg/ha

The nursery ponds require subsequent poisoning for selective killing of the larger planktonic copepods. These copepods are predatory in nature and instead of serving asfood for the delicate spawn and early fry, they attack and prey upon them resulting in poor survival. For this reason 4–5 days prior to stocking of spawn, the pond shouldbe treated with malathion at the rate of 0.25 ppm (active ingredient) for selective killing of the planktonic copepods. This treatment significantly increases the survival innursery ponds (Kumar et al., 1986). Such treatment is not required in rearing and stocking ponds.

9.1.2.3 Calculation of dose

The required quantity of poison can be calculated using the following formulae.

For rectangular ponds:

= Required amount of poison in kg.

For circular ponds:

= Required amount of poison in kg.

9.1.3 Eradication of predatory insects

Many aquatic insects in their larval and/or adult stages, prey upon fish hatchlings and fry and also compete with them for food. The common insect predators are beetles,bugs and dragonfly nymphs (Fig. 36). Among beetles, diving beetle (Cybister), water scavenger beetle (Sternolophus) and whirling beetle (Gyrinus) are more dangerousforms. Back swimmers (Anisops) appear in swarms in manured ponds during rainy season and cause heavy damage. Other predatory members of this group are waterscorpion (Laccotrephes), giant water bug (Belostoma) and water stick insect (Ranatra). Dragonfly nymphs are highly predatory on carp spawn.

Proper prepration of nursery ponds for stocking with spawn thus also aims at total eradication of such predatory insects. The basic method is to apply a thin oily film overthe pond surface which chokes the respiratory tubes of aquatic insects. The spawn and fish food organisms remain unaffected. Some of the common treatment methodsare presented in the following table (Table 25).

Table 25Pond treatment methods for eradication of predatory aquatic insects

Treatment method Dose/haSoap oil emulsion 56 kg vegetable oil + 18 kg soapDiesel oil 50 – 60 1Kerosene oil 80 – 100 1Turpentine oil 75 1Diesel emulsifier Diesel 50 1 * emulsifier 37.5 ml + water 2 1.

ADVERSE ENVIRONMENT FAVOURSPATHOGEN PROLIFERATION AND CUASESTRESS TO FISH

BETTER ENVIRONMENT FAVOURS FISHPREVENT QUICK PROLIFERATION

HOST PATHOGEN ENVIRONMENT-INTERACTIONSRESULTING DISEASE-OUTBREAK

HOST PATHOGEN ENVIRONMENT INTERACIONRESULTING IN ’NO DISEASE‘ CONDITION

H-SUSCEPTIBLE HOST AE-ADVERSE HOST P - VIRULENT PATHOGEN

Figure 36. Common Insect Predators in Nursery Pond

Except for soap-oil emulsion other mixtures or emulsion are easily prepared by simple mixing. For making soap-oil emulsion, the soap is mixed with oil and gently heatedfor some time with vigorous stirring. These emulsions are applied by spraying over the pond surface about 12–24 hours prior to stocking of spawn. It is the film of theemulsion which is important and hence care is taken not to disturb the film for a few hours. Windy days should be avoided as it will break the film.

Malathion application in nursery ponds also controls the predatory insects population and hence subsequent treatment for control of insect is not required. However, ifswarms of these predatory insects are seen in the nursery pond, treatment should be applied immediately.

9.1.4 Fertilization of ponds

Fertilization schedule involving both organic and inorganic fertilizers starts 10–15 days prior to stocking and is prepared on the basis of nutrient status and chemicalenvironment of the pond soil and water.

9.1.4.1 Basis of fertilization

In undrainable ponds where the frequent change of water is a remote possibility, the physico-chemical properties of pond water governing the biological production cycleare more or less a reflection of the bottom soil. The organic and mineral constituents of the soil play their part in releasing the required nutrients into water for pondproductivity through chemical/biological processes. Pond bottom soil also provides suitable substrates and necessary environment for the microbial decomposers - theliving fertilizer factory of the pond. Thus it is the soil condition and its nutrient status that forms the basis of pond fertilization by using either organic manure or inorganicfertilizer or a combination of both. Important characteristics of pond soil which influence fertilizer use is briefly described here.

Texture of the soil: The texture of pond soil, i.e. mechanical composition of the soil comprising sand, silt and clay and organic matter content, basically influences theeconomy of both inherent and added nutrients. Sandy and very clayey soil are not desirable as in the former the nutrients are lost due to heavy leaching; while in the latter,due to high adsorption capacity, the nutrients from the water are trapped. Clay minerals and organic matter of the bottom mud are both colloidal in nature and thus exhibitcolloidal properties like adsorption and cation exchange phenomenon. Sandy soils, on the other hand are low in colloidal substances and also deficient in organic humus.These are important considerations for deciding the application of fertilizers and manures.

Soil pH: As in water, pH of soil is also one of the critical factors affecting pond productivity. Under anaerobic condition the decomposition of organic matter is slow andthe products of decompositions are mainly reduced compounds and short chain fatty acids thus making the soil strongly acidic. Soil pH also influences transformation ofphosphorus into available forms and controls the adsorption and release of essential nutrients at the soil-water interface. Both for soil and water a slightly alkaline pH isconsidered favourable for fish ponds.

Availability of essential mineral nutrients such as phosphate, nitrogen, potassium, carbon and calcium is a consideration which determines the quality and quantity offertilizers to be applied. Nitrogen is required in large quantities as it is the basic and primary constituent of protein and chlorophyll. Although, phosphorus is required in asmall quantity compared to nitrogen, it is considered as the single critical element for maintaining aquatic productivity. Banerjee (1967) classified the undrainable pondsinto low, medium and highly productive groups, on the basis of their nutrient status considering mainly nitrogen, phosphate and organic carbon (Table 26).

9.1.4.2 Fertilization schedule

Proper analysis of soil and water is essential before deciding on the fertilization schedule. Detailed recommendations have been made in the chapter on pondenvironmental monitoring (Section 9.3.3).

Table 26Nutrient status of high, medium and low productive ponds

Available nutrients Productivity level pH N(mg/1000 g soil) P2O5 (mg/1000 g soil Organic carbon (%)

High 6.6 – 7.5 50 or more 6 – 12 1.5 or moreMedium 5.5 – 6.5 25 – 49 3 – 5 0.5 – 1.4Low Below 5.5 Less than 25 Less than 3 Less than 0.5

Liming: Diurnal changes in pH values ranging from pH 5 during the night and pH 11 during the day due to community respiration and photo-synthesis is a commonexperience but such wide variations impose stressful conditions for the fish. An adequate level of calcium in the pond provides a buffering system as shown in Figure 37.

Liming helps to raise the total alkalinity level and consequently the reserve CO2 will increase the availability of carbon for photosynthesis by raising the bicarbonateconcentration in water. This raised level of reserve CO2 will also prevent biological decalcification.

Figure 37. Mechanism of Buffering Action of Line

Depending on the pH of the soil, the dose of the liming should be Adjusted as per the following table (Table 27). Alkalinity can also be used as an indicator of the need forlime in fish ponds.

The total dose of lime calculated as per the table, need not be applied at one time. It may be divided into 3–4 doses and the first dose may be applied about a week priorto the manuring of the pond. It helps in faster mineralisation of organic matter in the pond sediment and acts as a prophylactic agent as well. The same dose is applicablefor nursery, rearing and stocking ponds. However, as and when needed during the culture period, additional doses of lime can also be applied.

Table 27Requirement of lime for different types of pond soils

Soil pH Soil type Requirement of lime(kg/ha)4.0 – 4.9 Highly acidic 2 0005.0 – 6.4 Moderately acidic 1 0006.5 – 7.4 Near neutral 5007.5 – 8.4 Mildly alkaline 2008.5 – 9.5 Highly alkaline Nil

Manuring: Organic manuring besides being important as means of adding the nutrients, is also equally important for improving the soil texture. A combination of organicmanures and inorganic fertilizers is considered more effective than using either of these alone. However, in nursery ponds, use of mineral fertilizers is not recommendedas the application may cause blooms of algae which may persist and may harm the young fry. Cow dung at an initial dose of 10 000 kg/ha may be applied in the nurseryponds about two weeks prior to anticipated stocking. If the pond is poisoned by mahua oil cake, then the dose should be restricted to 5 000 kg/ha. If two or more crops offry are to be produced during the season from the same nursery ponds, then the pond should be fertilized with 2 000 kg/ha of cattle dung about a week before eachsubsequent stocking. In case of poultry manure the dose should be only 33% of the cattle dung. Rearing ponds are initially manured with the raw cattle dung about twoweeks prior to stocking. The rate of application is between 5 000 – 7 000 kg/ha in 5 instalments. If the pond is treated with mohua oil cake then the dose of organicmanuring is reduced to half. Dose of inorganic fertilizers may be regulated as per pond soil productivity determined by detailed analyses. In the absence of soil testingfacilities a general recommendation should be followed. In such cases inorganic fertilizers are applied at the rate of urea 140 kg/ha and triple superphosphate 60 kg/ha in4–5 instalments.

In stocking ponds a combination of organic and inorganic fertilizers is considered more effective. Initial manuring with organic manure at the rate of 20% of the totalrequirement is done 15 days prior to stocking and the remaining 80% of the organic manure is applied in 11 equál monthly instalments during the rearing period. However,if mohua oil cake is applied earlier, the initial manuring is not essential.

The total quantity of inorganic fertilizers to be applied is decided according to soil type (Table 28) and applied in equal monthly instalments. The monthly instalments oforganic and inorganic fertilizers are applied alternately allowing a gap of a fortnight between the two applications. Nitrogenous fertilizers are selected on the basis of soilpH.

Table 28Amount of fertilizers required for ponds having

high, medium and low levels of productivityPond productivity levels

High Medium LowRate of application of fertilizer (kg/hg/y)Cattle dung 5 000–8 000 8 000–10 000 10 000–25 000Urea (43–45%) 112–155 156–225 226–260Ammonium sulphate (20.5%) 225–330 - -Calcium ammonium nitrate (20.5%) - 350–500 501–650Single super phosphate (16–20%) 156–219 220–315 316–405Triple super phosphate (40–45%) 54–75 76–110 111–145

In the absence of proper soil testing facilities fertilization schedule in stocking ponds may be followed as per the following table (Table 29).

Table 29Generalized fertilization schedule for stocking ponds (CIFRI, 1985)

Item Quantity(kg/ha) Periodicity of application

A. Cattle dung 2 000 Initial dose Cattle dung 1 000 MonthlyB. Urea (pH 6.5–7.5) or 25 Monthly Ammonium sulphate (pH above 7.5) or 30 Monthly Calcium ammonium nitrate (pH 5.5–6.5) 30 MonthlyC. Single super phosphate or 20 Monthly Triple super phosphate 8 Monthly

9.2 Stocking

Complete detoxification of the piscicide applied earlier should be ensured before stocking the nursery, rearing and stocking ponds. One or two days prior to stocking, ahapa should be fixed in the pond and some stocking materials should be put inside the hapa. Absence of distress and mortality after 24 hours confirm completedetoxification and the pond should be regarded as ready for stocking.

9.2.1 Stocking of nursery ponds

Carp spawn requires natural feed immediately after stocking and hence it is essential to have a minimum plankton value of 30–40 ml/m3 in case of stocking at a moderaterate (1.5–2.5 million/ha). When a higher stocking rate is to be adopted, plankton population is also required to be increased accordingly. In case the stocking density isover 5 million/ha, the plankton volume should be around 100 ml/m3.

Self-produced or procured 3–4 days old spawn should be stocked in the morning at the rate of 4–6 million/ha. The stocking density must be according to the condition ofthe pond and the amount of fish food organisms available. The rate of stocking in a well prepared nursery pond with adequate fish food organisms can be as high as 10million/ha. However, the survival level decreases with the increase in stocking density (Sen, 1976), (Table 30).

Table 30Survival of carp fry at various stocking densities

Survival level (%) Stocking density (million/ha)87.3 2.574.6 3.7562.0 6.2566.2 10.00

Combined rearing of two or more species of spawn should not be done in nursery ponds. The pond should be stocked after three days of hatching when their sizes rangefrom 0.6–0.75 cm and counts on an average about 500 numbers/ml. The required number of spawn are measured with the help of metallic or plastic sieve cups of knownvolume. Spawn are reared in nursery ponds up to fry stage for about 2–3 weeks when they usually attain 2–3.5 cm in length and 0.15–0.75 g in weight. At higher stockingdensity the growth is relatively slow. It is possible to raise 3–4 crops of fry from the same pond during the same breeding season and in addition, the pond can also beutilized for rearing of common carp seed during January to March.

9.2.2 Stocking of rearing ponds

Rearing of fry to fingerling stage is done in rearing ponds where fry are stocked at the rate of 0.25–0.30 million/ha with a survival level of 60–80% under proper pondconditions. Either monoculture or polyculture methods can be adopted for this rearing.

In the case of polyculture the species combination and their ratio should be decided on the basis of their habit, feeding, availability of feed, etc. Some of the possiblecombinations are - catla, rohu, mrigal, common carp (3:4:1:3); silver carp, grass carp (1:1); silver carp, grass carp, common carp (4:3:3); catla, rohu, mrigal, grass carp(4:3:1.5); silver carp, grass carp, common carp, rohu (3:1.5:2.5:3), etc. Combination of too many species should be avoided as it invites excessive handling at the time ofharvesting for species segregation. Fry are reared in ponds for about 3 months when they usually attain 100–150 mm in length and 15–40 g in weight. For healthy fryrearing it is recommended that the size of the fry at the time of stocking in the rearing pond should be as uniform as possible. This can be done by size grading at the timeof fry harvesting from nursery ponds. Prior to stocking the rearing ponds the pond waters must have a plankton level of about 30–50 ml/m3.

9.2.3 Stocking of grow-out/stocking ponds

After proper preparation, the pond should be stocked with 100–150 mm long fingerlings of desired carp species. In case the fingerlings are not available, the pond canalso be stocked with advanced fry or early fingerlings in absolutely predator-free ponds. The stocking rate depends primarily upon the volume of water and on the oxygenbalance of the pond. Quality of available natural fish food in the pond and the capacity of the farmer to provide supplementary feed, are also matters for consideration.Usually a pond having average water depth of 1.5–2.5 m should be stocked at the rate of 5 000 fingerlings/ha. The volume of water available for fish in an undrainablepond should not be less than 2 m3/fish if there is no provision of artificial aeration. In composite fish culture, rearing of six species of carps, viz. catla (Catla catla), rohu(Labeo rohita), mrigal(Cirrhinus mrigala), silver carp (Hypophthalmichthys molitrix), grass carp (Ctenopharyngodon idella) and common carp (Cyprinus carpio) isconsidered to be the ideal combination. However, depending on the availability of quality fingerlings of these carp species, three or four species combinations can also betaken up. Ratio of different species in the combination is also equally important. However, there are certain general guidelines for selecting species combinations (Table31).

Table 31Different species combinations and theirstocking ratios for composite fish culture

Species combination Surface feeder Column feeder Bottom feeder Macrophyte feeder Catla Silver carp Rohu Mrigal Common carp Grass carp

3 40 - 30 30 - -

4 30–40 - 20–30* 15–20 20–25 -

6 10–15 20–30 15–30* 15–20 20–25 5–15

* Lower units in shallow ponds

Availability of weed in the pond or in the vicinity decides the stocking density of grass carp. In older ponds where the soft sediment layer of the pond bottom is usually verythick and anaerobic in nature, the ratio of bottom feeder and especially the common carp should be kept at a higher level. Likewise, the relative density of column feeder-rohu should be kept on the high side in deeper ponds than in shallower ponds, whereas ponds showing consistently higher zooplankton population should have a higher

ratio of surface feeders. Based on the performance of individual species in the combination and availability of seed, combinations can be modified in subsequent years.Silver carp, however, should be stocked 1 or 2 months later. Interspecies competition for food between catla and silver carp to some extent is the key point for suchdifferential stocking. The stocking pond also should have a desired level of plankton population of about 30–50 ml/m3.

9.2.4 Method of stocking

Stocking of spawn, fry and fingerlings should be done very carefully to avoid any post-stocking mortality due to shock or infections. To minimize post-stocking mortality thefry/fingerlings should be slowly and gradually acclimatized to the temperature and quality of the water in the stocking pond. To do so, open the mouth of the seed transportbag/container and gradually add the pond water in phases and after 15–20 minutes slowly dip and tilt the bag/container in the pond so that the spawn/fry/fingerlings arefree to swim out. Stocking should preferably be done in the cool evening hours. Apply prophylactic treatment to seed prior to their release so as to avoid any post-stockinginfections (Section 9.3.4).

9.3 Post-stocking management

Post-stocking management involves harnessing the pond productivity in the form of natural fish food, maintenance of pond environment congenial to the cultivated fish andfish husandry, mainly feeding and health care.

9.3.1 Feeding

Soon after stocking, the fish start grazing natural food available in the pond irrespective of their stage of life cycle. Spawn feeds voraciously on plankton. Therefore,immediate steps must be taken for providing supplementary feed. In the case of nursery ponds where spawn are reared for about a fortnight up to fry stage, supplementaryfeed is broadcoast on the pond surface in the form of fine powder daily in the morning hours at prescribed rates (Table 32).

Table 32Rates of daily supplementary feeding at various stages of culture

Stage Daily feeding rateSpawn to fry 4–8 times of the initial body weightFry to fingerlings 50–100% of the initial body weightGrowers 1 – 2%Brood fish 1 – 3%

The following schedule of feeding should be followed for nursery ponds (Table 33).

Table 33Feeding schedule for nursery ponds

Period (Day from the date of stocking) Rate of feeding Amount of feed for 0.1 million of spawn1 – 5 4 times the total initial weight 560 g/day6 – 12 8 times the total initial weight 1 120 g/day13 No feed -14 Harvesting

At the time of stocking, the spawn of 0.65–0.75 cm average length weigh about 0.0014 g each, and a mixed collection of 0.1 million weigh about 140 g.

Grass carp is fed its preferred aquatic vegetation or green animal fodder as per the following table (Table 34). See Fig. 38.

Table 34Feed for grass carp during various stages of life cycle

Stage FeedFry (1.7 – 3.9 cm) Soft macrophytes such as Azolla, Wolffia, Lemna and Spirodella, etc.Fingerlings (4.0 – 15.0 cm) Hydrilla, Ceratophyllum, Vallisneria, Najas, Chara, etc., in addition to those mentioned above.Juveniles/Adults (above 15.0cm)

In addition to above, green animal fodder such as barseem, napier, hybrid napier, elephant grass, tender leaves of vegetables and trees such as soobabul,drumstick, etc.

Figure 38. Feeding Enclosure for Grass Carp

The form in which the supplementary feed is given is also important. In the nursery ponds the feed should be provided in finely powdered form and may be broadcast overthe pond surface. In the case of rearing, stocking and brood stock ponds, the supplementary feed mixture should be mixed with enough water to make a dough andapplied into feeding trays fixed in the ponds. Better results can be obtained if the feed mixture is pelletized and fed to fish (Fig. 33B). The pellets may be of the sinking orfloating type, but both types should be water stable. The sinking type of pellets are put in feeding trays fixed in the pond.

The standing crop of fish is estimated every month on the basis of sample netting for growth and health check and feeding schedule is adjusted accordingly. Periodicalnetting should be done strictly on a monthly basis and with the help of hand nets and spring balance (Fig. 39), the average weight of each species should be recorded(Table 35). The average weight of individual species, monthly increment in weight, total standing crop and amount of feed to be given should be estimated on the basis ofdata thus available.

The feeding tray should be cleaned daily before the application of fresh feed. Fish normally stop feeding if they are sick or the temperature is far below normal. In suchsituations a proper health check is required and the feeding rate is adjusted. Grass carp should be fed until they stop eating. Usually they consume aquatic vegetation,about 50% of their body weight on a daily basis.

Table 35Data sheet for monthly netting

Speciesstocked

Av. wt. of 10 fish (g) Av. wt. of thismonth(g)

Av. wt. of lastmonth(g)

Monthlygrowth (g)

No. of fishstocked

Total estimated crop(kg)1 2 3 4 5

(Samples)Catla 11000 11000 11500 11250 11750 1 110 1 025 85 150 166.500Rohu 6000 7000 7500 7000 7500 700 650 50 200 140.000Mrigal 9000 9500 9000 9500 9100 922 850 72 200 184.400Silver carp 22000 22750 22500 22500 22250 2 240 2 000 240 150 336.000Grass carp 50000 50500 50000 45500 48000 4 880 4 300 580 100 458.000Common carp 12000 12600 12000 12500 12500 1 232 1 150 82 200 246.400 Estimated total standing crop 1531.300Amount of feed to be applied daily at the rate of 2% body weight 30.6 kg

Av. wt. - Average weight

9.3.2 Periodic fertilization

The next step in post-stocking management is the periodic fertilization which ensures replenishment of nutrients and consolidation of the energy base for microbialdecomposition activities. The desired total quantity of fertilizers are best applied in small equal doses at periodical instalments throughout the rearing period so as toensure maximum utilization of these fertilizers. The mode, sequence and timing of application of fertilizers are important or achieving best results. Lime should be appliedfirst followed by the organic manure and finally the inorganic fertilizers an the same order is followed subsequently. These fertilizers should be applied only when thephysical conditions of the water are most suitable such as plenty of sunlight, adequate oxygen, optimum temperature, adequate water level and low wind velocity. Turbidwater with a high content of suspended solids are not preferred. Fertilizer should be sprayed or distributed properly over the water surface during the day time when thetop layer of water is warmer and lighter. Inorganic fertilizer application must be stopped temporarily when the nitrate and phosphate content of water show a level of 0.5ppm or above at any stage during the periodic pond environment monitoring. Similarly, organic manuring may also be stopped if the soil organic carbon level goes beyond2%. However, normal application may be resumed after the specific nutrient level goes down. Care should be taken to see that the phosphatic fertilizers dissolve properlyin the water since powdered orgranular fertilizer may often solidify after coming in contact with water. It is more effective if doses are divided further so that application ismore frequent. The results are encouraging when organic manures are applied in daily doses in pons. The desired amount of cattle dung is mixed with water and uniformlyspread over the entire pond surface. In nursery ponds the first manuring is done two weeks prior to stocking and if more than one crop is nursed, fresh manuring shouldbe done a week prior to every subsequent stocking.

Figure 39. Hand Net and Spring Balance

A periodical fertilization schedule is summarized in Table 36. The rate of fertilization by organic and inorganic manures has already been discussed (para 9.1.3.2).

Table 36Periodicity of fertilization in nursery,

rearing and stocking pondsPonds Manure Periodicity

Nursery ponds Organic manure 3 weeksRearing ponds Organic manure and Inorganic fertilizer 3 weeks - dailyStocking ponds Organic manure and Inorganic fertilizer Monthly

9.3.3 Pond environmental monitoring

9.3.3.1 General considerations

Proper pond management involves a regular and steady supply of nutrient for sustained production of fish food organisms. The supply of nutrients could be from within thepond itself or from outside. It is also required to regulate the physico-chemical parameters of the pond ecosystem within the safe tolerance limits of the cultured fishspecies. This necessitates periodical monitoring of pond environment and taking corrective measures in time. Olah and Sinha (1984) have developed a practicalmonitoring system of perennial undrainable ponds which offer the monitoring of basic architecture and production processes of such pond ecosystems in tropical monsoonlands. The system needs simple instrumentation, little working time and labour and reveals sufficient information about the actual nutrient level of pond sediment andwater. Most of these parameters can be easily measured at the pond site while some require laboratory facilities. The monitoring system gives reliable guidelines for fishfarmers to optimize fish production.

9.3.3.2 Parameters to be monitored

It is essential for extension workers to name and code-number the ponds in their area. Such coding may be based either on postal district/unit/village farmer's name, etc.The fish farmer should record the following information on his fish farm:

Nature of pond: Perennial or seasonal; nursery pond, rearing pond or stocking pond.

Water area: Measurement of the water area is essential in order to know the size of the pond for proper fish stocking and quantifying the production processes. This canbe done easily with the help of a bamboo pole of known length.

Age: Age is one of the most important parameters, since it has direct relevance with the productivity of the pond which usually varies from one year to several hundredyears.

Management: Management status should record the existing management techniques and its level (intensive or extensive). The species of fish present, details ofculture activities, stocking structure and density, fertilization, feeding, harvesting, marketing, etc, need to be recorded. To obtain qualified data on the organic carbon andbiogenic nutrient load it is necessary to know the number of livestock and human population associated with the particular pond.

The fish farmer should also monitor the following parameters on a routine basis.

Water colour: The visual colour of the pond water is a simple but important reflection of the basic production processes.

Water transparency: Water transparency measured with a Secchi disc is intended to quantify the result of those processes which determine and modify the visualcolour. However, a low transparency may result either from high turbidity alone or from dense algal population and thus cannot reflect the correct trophic or productionlevel of the water. However, the Secchi transparency readings together with the visual colour provide valuable information on the productivity of the water.

Water depth: The primary water source is usually the rainfall during the monsoon. After the rainy season the water level gradually decreases which results in a veryshallow water column by the end of the dry season. The water depth can be measured with a 4–5 m long bamboo pole fitted at its base with a wooden disc of 25 cm dia.

Soft sediment depth: A soft sediment layer is usually present in the pond bottom. The depth of this layer can be measured with a 6–8 m long bamboo pole having awooden disc of 10 cm dia at its base.

Solid sediment depth: In older ponds, in addition to the soft sediment layer, a solid sediment layer with a low water content is also present. The thickness of the layercan be measured with a 6–8 m long bamboo pole with a sharp end. The total thickness of the soft plus solid sediment layers has a direct relation to the age of the fishpond, at times the sediment layer measures more than 2 m. Such thick sediment, having a rich nutrient content, is anaerobic in nature with slow bacterial decompositionand mineral cycling rates. This should be properly utilized for fish culture.

Chemical environment in the water column: The water is chemically characterized by pH, alkalinity, NH4-N, NO3N and PO4-P measurements following standardmethods. Normally the pH and alkalinity do not change from pond to pond on the same types of maternal soil. The measurements of NH4-N, NCO3-N and PO4-P indicatethe basic inorganic nutrient status of the pond.' Simple chemical parameters such as dissolved oxygen and pH may be measured using field kits. Slightly alkaline water(pH 7.0–8.5) and oxygen levels of 6–9 ppm indicate optimum condition.

Dawn oxygen: Fish ponds usually exhibit wide fluctuations in the dissolved oxygen content from day to night. This diurnal oxygen fluctuation is normally measured tocalculate the community metabolism of the whole pond while quantifying the production and respiration processes in the ecosystem. A single measurement just beforesunrise would be an important indicator of the risk of fish kill due to oxygen depletion. Desirable ranges of various pond environment parameters are presented in Table37.

Table 37Desirable ranges of pond water quality parameters

Parameters Desirable rangeWater colour Greenish brownTransparency 25 – 50 cmpH 7.0 – 8.5Dissolved oxygen 5.0 ppmFree carbon dioxide 15.0 ppmInorganic nitrogen 0.2 ppmInorganic phosphorus 0.2 ppm

A simple schedule for monitoring the important parameters is presented in Table 38.

Table 38Environmental monitoring schedule

Periodicity Parameters Daily Weekly Fortnightly Monthly Quarterly

A. Water Water colour x - - - - Transparency - x - - - Temperature x - - - - Depth - - - x - pH - x - - - Free CO2 - x - - - Alkalinity: Total - - x - - Bicarbonate - - x - - Dawn Dissolved O2 x - - -

NH4-N - - - x -

NO3-N - - - x -

PO4-P - - - x -B. Soil Sediment depth - - - - x pH - - - x - Organic carbon - - - - x Total nitrogen - - - - x Total PO4-P - - - - x

9.3.4 Fish health monitoring

In most of the situations, cultured fish are healthy even in the continuous presence of pathogens. However, when environmental stresses occur and the balance shifts infavour of the disease, the characteristic pathogens flourish. Under such circumstances if the fish fail to adjust adequately or if corrective measures are not taken timely,outbreak of diseases may occur. By resolving environmental problems and applying effective therapeutics, the original balance between the host and the pathogen may berestored. Thus a disease outbreak may often be a symptom of environmental imbalance and it gives a distress signal so that the adverse environmental conditions mayimmediately be corrected to prevent fish losses. The approach to health care in composite fish culture in undrainable ponds is essentially one of management ofecosystem and fish husbandry.

9.3.4.1 Host-pathogen-environment linkage

Susceptible fish, the virulent pathogen and the aquatic environment in which they encounter each other are the three contributing factors in fish disease outbreaks(Snieszko, 1974). The fish itself possess a varied and complex defense system, the immune system, the potency of which determines the susceptibility or resistance to theparticular pathogen under a particular circumstance. Several environmental components effectively influence the normal immune mechansim of the fish when their valueexceeds the normal tolerance limits. A virulent pathogen, when present in the surrounding, is usually capable of causing an infectious disease to fish under stress. Thecausative agents of the disease and their fish hosts carry on their struggle in the aquatic environment and the environmental parameters which influence this encountermay shift the balance from one side to the other and often determine whether the host will overcome the infection or the pathogen will flourish (Fig. 40).

Some of the infectious and parasitic agents can survive only in live fish, and in such cases the disease transmission is from fish to fish. Such disease-producing agents are

true pathogens. Others are extremely adaptable organisms which can survive outside the fish and cause infections whenever fish are weakened or otherwise predisposedto disease due to environmental stress. Most of the fish disease agents belong to this category.

9.3.4.2 Health monitoring programme

Health protection of cultured fish is considered to be one of the most important aspects of modern aquaculture systems including the composite fish culture which requiresa programme basically to check the health status of the fish quite frequently and employment of fish health management measures. This enables timely detection of anydisease outbreak and taking up proper treatment measures at the initial stage. Otherwise, in advanced stages of the disease, control and treatment measures do notprovide economical and effective.

A fish health monitoring programme should consist of the following components:

i. Daily observation of fish in each pond.

ii. Sampling and examination of fish at regular intervals for health check and diagnosis of the disease if any.

iii. Monitoring of pond quality and sanitation.

iv. Sampling and examination of fish at the onset of distress, disease outbreak or mortality.

Figure 40. Effects of Environmental Changes on Fish-Pathogen Relationship

The sampling for health check of fry and fingerlings should be done at weekly and fortnightly intervals respectively, while in composite fish culture ponds it should be atleast once a month. A thorough health check of fry/fingerlings is required 1 or 2 weeks before netting out for stocking in grow-out ponds or before transfer to another pond.Such an examination will provide sufficient info rmation for planning.

Diseased fish may exhibit either or both physical and behavioural signs, the most common of those are listed below:

Behavioural signs:

slowing down or a complete stoppage of feeding;

loss of equilibrium, swimming erratically or in spirals;

surfacing for gulping air and scraping against the floor and sides of the pond.

Clinical symptoms:

excess mucous secretion;

change in normal colouration;

erosion of scales, part of fins, skin, etc.;

decolouration or paling of gills;

abdominal swelling;

bulging of eyes;

presence of cysts, spots or patches over the body and gills, etc.;

appearance of lesions, haemorrhagic spots and greyish or brownish areas over the body.

Laboratory examinations:

Thorough visual examination for external signs of the disease should be followed by detialed but quick laboratory examination by pathomorphologica, pathoanatomical andmicroscopical studies of squash and smear preparation from different organs/tissues. Diagnostic procedures in brief are presented below (Table 39).

In situations where a disease problem is suspected, only those specimens exhibiting symptoms of distress or disease should be selected. Live moribund speciments arepreferred, but if necessary, freshly dead specimens may also be collected for laboratory examination.

Table 39Methods for diagnosis of commonly occurring diseases of Asiatic carps in undrainable ponds

Disease agent Method ofexamination Positive indications

A. Parasites1. Protozoa Ichthyophthirius Microscopy Pin-head size white spots on the skin, fins and gills. Presence of ciliated trophozoites with relatively large horseshoe shaped nucleus. Trichodina Microscopy Presence of saucer-shaped actively moving ciliate parasites on body surface and gills. Myxozoans Microscopy Presence of cysts, spores on gills, body surface and/or in the squash preparations of kidney. spleen, air-bladder, etc.2. Crustaceans

Arqulus Visual examinations/microscopy

Haemorrhagic spots, lesions over the body and presence of parasites attached to fish body by means of suckers and hooks.

3. Flukes

Gyrodactylus/Dactyloqyrus

Microscopy Presence of parasites in gills and skin.

Diplostomum Visual examination/microscopy

Small pigmented black nodules over the body surface

B. Fungi1. Saproleqnia Microscopy /visual

examinationBody lesions associated with small white tufts of hyphae on fins and skin. Infected fish eggs fail to hatch and show presence of fungusmycelium protruding from the egg surface.

2. Branchiomyces Microscopy Decolouration of gills, erosion of lamellae and presence of fungal hyphae in blood vessels.3. Achlya Microscopy Cottony outgrowths of fungal mycelium over the infected area.C. Bacteria1. Aeromonas hydro-

philaCulture/microscopy Dropsy condition and haemorrhages over the body.

2. Pseudomonasfluodrescens

Culture/microscopy Clinical condition is usually indistinguishable from that of aeromonas. Haemorrhages over the body.

3. Flexibacter columnaris Culture/microscopy Appearance of external lesions on the body, head region and gill. Lesions initially begin as whitish or brownish patches with reddish zonearound the periphery.

D. Virus1. Rhabdovirus of

common carpCell culture/serumneutralization test

Common carp is prone to this disease showing dropsy condition.

2. Rhabdovirus of grasscarp

Cell culture/serumneutralization test

Only grass carp is prone to this disease exhibiting similar dropsy symptoms.

Smear preparation of selected tissues and organs may be made on the spot by smearing the material on a slide. Slides can then be dired, stained and examinedimmediately. Bacteriological media can be inoculated with materials from various organs, especially kidney, heart, etc., employing aseptic techniques. On-site diseasediagnosis permits the immediate application of chemotherapy or remedial measures to control or eradicate the disease. However, accurate diagnosis of disease is ofutmost importance if proper treatment is to be applied and this is possible only through experience and training. At times, may disease conditions occur which cannot beproperly diagnosed without specialized laboratory facilities and in such conditions samples should be sent to such laboratories under proper preservation, packing andshipment (Dey, et al., 1982). As far as possible the specimen for examination to reference laboratories should be always sent live but when circumstances prohibit livedelivery, specimens may be forwarded packed in ice. Specimens for parasitology examinations may be preserved in 5–10% formalin solution. In case of larger specimensincision may be made to facilitate effective penetration of the fixative. The volume of fixative should be at least five times the volume of materials to be preserved.

9.3.4.3 Health management measures

Understanding and managing the undrainable pond environment is the key to successful fish health management and profitable fish culture, and to ensure this theknowledge of the role of various environmental components in the occurrence of disease outbreak is essential. The main thrust of such measures is directed toward:

minimizing the stress on cultured fish;

prevention of the introduction of serious disease agents;

confinement of disease outbreaks to affected areas;

minimizing losses from disease outbreaks.

The following important measures are the key components of successful fish health managements (Figure 41).

Surveillance and maintenance of water quality: Abrupt and wider fluctuations in some of the environmental parameters such as dissolved oxygen content, pH,turbidity, temperature, additions of some chemicals, detergents, pesticides and naturlaly produced toxic substances such as hydrogen sulfide, ammonia, dinoflagellatetoxins, etc., often cause stress in fish and predispose them to infectious diseases. Anything that alters the environment of the fish is a potential stressor and efforts shouldbe made to identify and avoid them. Undrainable ponds offer great protection against spreading of disease outbreaks by confining the outbreaks only to the affected ponds.However, the recent trends of intensification in aquaculture involve high stocking rates, increased feeding and fertilization programmes resulting in nutrient accumulationleading to appearance of algal blooms that lead to dissolved oxygen and other water quality problems. In older ponds, cases of excessive accumulation of organic matterhave been observed, resulting in the appearance of bacterial bloom and related oxygen depletion (Radheyshyam et al.,). For health and optimum growth, the dissolvedoxygen level should not drop below 5 mg/1. Carbon dioxide concentration up to 20–30 mg/l may be tolerated by fish provided oxygen is near saturation. At lower levels ofdissolved oxygen, toxicity of carbon dioxide increases. When pH values remain above 9.5 or below 6.0 for extended periods, fish will be under stress and may not growwell. Liming agents may be used for low pH corrections. Ammonia concentration above 1.0 mg/1 indicates organic pollution. Hydrogen sulfide toxicity increases withdecreasing pH and it is harmful even at 1.0 mg/l concentration level. Making the pond environment more congenial and hygienic, eliminates the risk of stress and providessafety to fish. Proper and timely management of soil and water qualities by manipulating feeding, fertilization, liming, addition of clean water, bottom raking, aeration ofwater by recirculation or splahsing, etc., reduces most of the environmental problems and provides congenial conditions for the health growth of fish. An interval of about15 days between the pond poisoning and the stocking eliminates most of the pathogens from the environment.

Figure 41. A Model for Integrated Fish Health Management System

It is always advisable to stock the pond only with healthy and genetically vigorous fry and fingerlings so that they may have better growth rate and resistance towardsdiseases. Prior to stocking, samples of the stocking material should be examined to check their health status. This avoids any risk of introducing infected stock in thepond. However, the stocking materials should also be prophylactically treated before releasing into the pond (detailed under Chemoprophylaxis).

Overstocking may lead to biological crowding resulting in waste build up, decreased availability of natural food, depletion of dissolved oxygen, deterioration of waterquality, etc., and hence it is advisable to follow the recommended stocking density for nursery, rearing and stocking ponds.

Minimizing handling stress: The rougher the handling, the greater is the stress and the risk of disease (Kumar et al., 1986). Care should be taken not to break theprotective mucous coating of the skin. During summer months netting should always be done early in the morning and it is better to have minimum possible handlingduring hauling. High temperature during hot water causes increased metabolic activity and induces more stress upon them.

Measures in pond management:

Poisoning of pond - Wild fish population is one of the most potential sources of disease-producing organisms. Use of chlorinated lime (bleaching powder) is the mostsuitable material for this purpose, since it kills all the wild fish species, molluscs, tadpoles, frogs, crabs, etc., and also disinfects the pond water and soil. It is applied at therate of 40–50 ppm (Tripathy et al., 1978). Mahua oilcake is also a widely used piscicide, but it fails to disinfect the pond. In nursery and rearing ponds it is desirable tohave second poisoning with malathion at the rate of 0.25 ppm 4 or 5 days prior to stocking. It eliminates the larger copepods which do appear in large numbers afterorganic fertilization. These copepods prey upon young fish larvae and also serve as vectors or carriers of many infectious pathogenic organisms. Some of the commoncrustacean fish parasites also get killed. Malathion application has significantly increased the survival level in nursery ponds (Kumar et al., 1986).

Disinfection of appliances - All required appliances such as fry carriers, hapas, utensils, buckets, nets and gears, etc., require thorough cleaning and disinfection beforebeing put to use. Some of the pathogenic organisms are found adhering to them and may cause disease if they are allowed to come in contact with the host fish species.Disinfection can be done by washing or immersing in a concentrated solution of disinfectant. Some of the most effective and easily available disinfectants for such use arechlorine, sodium hydroxide, sodium chloride potassium permanganate, etc. Chlorine is probably the most widely used disinfectant in fishery management and is easilyavailable as a solution of sodium hypochlorite and powder of calcium hypochlorite (bleaching powder). Solution of 1–2% chlorine is active against bacteria, viruses andfungi but is extremely toxic to fish and hence their residues must be thoroughly rinsed from the disinfected items before being brought into contact with fish. Sun drying ofnets, hapas, etc., is also a practical method of disinfection.

Proper feeding - In addition to the natural fish food which is made available by fertilization, an adequate amount of good quality supplementary feed is essential formaintaining healthy growth of fish. Any deficiency in quantity and quality of feed may cause various diseases by increasing susceptibility to many infections.

Prevention of entry of unwanted fish: Most undrainable ponds lack proper embankments. Most of these ponds have channels in the embankments connectingthem with outside waters during the rainy season. Most of the ponds lack even proper embankments. These channels are the vulnerable sites through which some of thewild unwanted fish species or other animals get entry to the pond. Fixing fine meshed screen into these channels may eliminate the risk of entry of unwanted fish speciesinto the pond. Pond embankments may also be raised to prevent risk of inundation and entry of undesirable animals and fish species. Some fish eating birds, molluscs,etc., serve as intermediate hosts for many parasites that infect fish. Tadpoles and frogs may also act as carriers of certain parasites and bacteria which ultimately mayinfect carp species and hence such animals should not be allowed in the pond.

Separation of young and brood fish: Brood fish may serve as carriers of disease causing organisms without exhibiting any clinical symptoms. They sometimesbecome survivors of previous epizootics due to built up immunity but retain some of the pathogens. To avoid such risk, the best course is to separate the young ones fromthe adults.

Removal of dead fish from the pond: Dead and apparently sick fish should be removed. A daily log of losses must be kept. Such records will provide valuableinsight into the problems and may lead to their solution.

Holding the fish in a hand net and dipping it into a concentrated solution of the drug for one minute or less is used as prophylactic treatment in case of mild diseases. Ashort bath is useful when facilities for a rapid flow of water are available. Water flow is stopped and relatively high concentration of the drug is added. Exposure timeshould not be longer than one hour. A long bath is a very effective method for prophylactic treatment of pond fish for external parasites. The oral route is used inprophylactic treatment to prevent certain infections. It is generally conceded that feeding medicated feed to fish is a prophylactic rather than a curative measure.

Prophylactic use of streptomycin and penicillin at the rate of 25 mg of streptomycin sulphate and 20 000 I.U. of penicillin has been found to be very effective in preventingoutbreak of columnaris disease in rohu in a field-oriented experiment (Kumar et al., 1986). Feeding antibiotics with feed has successfully prevented the occurrece of CE(Carp Erythrodermatics) in European carp culture. Prophylactic treatment of pond with locally available organophosphorous insecticide (malathion) at the rate of 0.25 ppmof active ingredient successfully prevents occurrence of trematode and copepod infections.

Occasional application of potassium permanganate at the rate of 2 or 3 ppm is recommended for increasing dissolved oxygen concentration and hauling prophylaxis. Diptreatment in 500–1 000 ppm solution of potassium permanganate for a few seconds before releasing adult fishin ponds is also a very effective and practical prophylacticmeasure. Short bath for a few minutes in 2 or 3% common salt solution is also a safe and inexpensive prophylactic measure against a wide range of parasitic an microbialpathogens.

9.3.4.5 Immunoprophylaxis

Immunization is becoming one of the most important ways of preventing communicable diseases in animals, including fish. Several commercial vaccines are now availableand being used in many developed countries. Vaccines for some of the bacterial diseases of carps which do occur in undrainable pond culture systems are also available.These vaccines are against Aeromonas hydrophila and Flexibacter columnaris. Viral vaccine against Spring Viremia of Carp (SVC) is also being used on a commercialscale very successfully.



More details

10. MANAGEMENT OF COMMON HAZARDSSuccessful management of any farming system should anticipate several incidental hazards and keepready remedial measures to deal with the situation. Based on the available data the commonly occurringserious hazards are discussed and remedial measures suggested.

10.1 Deficiency of dissolved oxygen

The most common and serious hazard in the composite fish culture ponds is the depletion of dissolvedoxygen level in the water. Gulping for air, especially during the early morning hours, is the most commonbehavioural symptom. The growth rate is seriously affected and very often it may result in a mass fish kill.Depending on the situation and availability of resources all such steps should be taken promptly whichmay help raise the DO level of the pond. The following steps are recommended:

Add freshwater in the pond by pumping it from nearby sources. To avoid entry of undesirable fish,use a screen around the mouth of the intake pipe.

Agitate the pond water by splashing, beating with bamboo poles, repumping with the help of apump or using a mechanical churner/aerator.

Apply potassium permanganate at the rate of 2–3 ppm.

Lime at the rate of 200 kg/ha and rake up the bottom.

Cut all the trees/branches shading the pond.

Stop feeding and fertilization till normality is restored.

10.2 Appearance of algal blooms

Algal blooms of Microcystis sp., Euqlena sp., etc., frequently occur causing serious problems again interms of dissolved oxygen. It creates situations where supersaturation of oxygen occurs during day timeand serious DO depletion takes place during the night, sometimes leading to a mass fish kill. Thefollowing remedial measures are recommended:

Apply chemical algicide Diuron simazine (Tafazine) at the rate of 3–5 ppm. However, mass killingand decay of algae may also cause DO depletion.

In small ponds cover part of the pond with duck weeds or other floating weed like Pistia to reducethe amount of sunlight entering the pond. This will result in the death of algal cells. Gradually coverthe whole pond, part by part.

Add fresh water if possible from nearby sources, taking care to prevent entry of unwanted fish.

10.3 Common carp problem

Because of early maturity and natural breeding, the rate and ratio of stocking of different carp species incomposite fish culture ponds are liable to get greatly altered during the grow-out period. This problem canbe overcome by placing at one corner of the pond some floating weeds such as Eichhornia during the

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breeding season. The common carp will deposit eggs on the roots of the floating plants. The followingmorning these plants are replaced by fresh plants and eggs are transferred to hatching hapas. Byadopting this technique the common carp population is efficiently controlled and sufficient quantity ofcommon carp seed is also produced (Fig. 42).

Figure 42. Eichhornia with attached common carp eggs

10.4 Problem of no rain and plenty of rain

During drought the water level drops down to critical levels in some ponds, while during seasons of heavyrains the incidence of flooding is not uncommon.

Keep constant vigil on water level. Before it drops below the 1.25 m mark, water should be addedfrom nearby sources. Keep alternative source of water ready for such occasions. A shallow tubewell could be of some help to fight against drought.

Harvest the fish before such a situation is encountered.

Repair and strengthen the dykes before the onset of rains. Entry point and spillway should beproperly guarded by strong fine meshed steel netting.

Harvest the fish before the flood season if cost of protection becomes too high.

10.5 Problem of predation

By far the most important and damaging predators of fish in ponds are otters, snakes, frogs, birds, etc.Otters can be prevented by putting a fence around the pond. Snakes, frogs and birds cause problemsmostly in nursery and rearing ponds. Ponds in the vicinity of the fish farmer's home are less likely to beaffected by these predators than the ponds that are isolated and seldom visited. Frogs normally lay eggsin shallow pits along the sides of seasonal nursery and rearing ponds during the first monsoon shower.All such spots should be identified and the eggs should be destroyed. Bird-scaring devices, including firecrackers should also be used if the problem becomes severe.

10.6 Poaching

Poaching is perhaps the biggest problem in freshwater aquaculture. High value and ready market forcarps make them more prone to poaching. The widely used gears for poaching are cast nets, gill netsand small drag nets. The following measures have been found to be most effective against such forms ofpoaching:

Place branches of trees and bamboo twigs in the grow-out pond along the sides. Nursery andrearing ponds are usually not prone to poaching.

Stretch and fix barbed wire in criss-cross manner in the pond, especially along the sides.

In large ponds, occasionally row a boat with hooks or barbed wire hanging from its keel to detectgill nets.

Fencing the farm with barbed wire and employing the services of watchmen are efficient means ofpreventing poaching.

Trained dogs used for night watch minimizes the risk considerably.

10.7 Leakages in embankment

Sometimes leakages do occur in embankments and if not checked immediately they could causeextensive damage to the pond embankment. If the leaking water is clear and flow velocity is sluggish itmay be seepage water and hence there may not be any immediate danger. In case the water flow is fastand muddy, immediate steps must be taken to locate the hole on both sides of the embankment. Muddywater shows soil erosion and washing away of soil particles. To locate the hole, heavy turf sod should bethrown on the water surface which gets attracted towards the hole and the sod may come out of the pondthrough the hole. Whirling action of water may be noticed just above the leak if it is big.

Leakages can be checked by pushing sawdust, bran, etc., into the upstream site. These are carried bywater into the leak where it swells and stops the leak. In case of major breaches which may occur andcause severe damage to the embankment, sufficient material and labour resources must be mobilised.The outside of the banks should be protected first to prevent further erosion. A semicircular bundh maybe constructed on the inside with brushwood, bamboo nettings and sand bags to facilitate repairing thebreached portions with earth and sand bags.

10.8 Outbreak of diseases

10.8.1 General considerations

The fish farming system in general is unique in that the cultured animal is cold-blooded or poikilothermicand lives in water, where the respiratory oxygen level is limited and may become lethal at times. Also,metabolic waste products, left-out feed materials and organic load of the pond bottom regularly come intocontact with certain vital organs and tissues. In an undrainable pond system no addition of water oraeration is normally done and the accumulated wastes are not usually removed unless provision is madeto desilt the pond after a couple of years. All such factors can cause deterioration of fish health andmagnify the risk of outbreaks of diseases.

There are two strategies for the management of this hazard, viz. prevention of disease throughprophylactic measures and treatment and control of disease outbreaks using fish therapeutics. There is acommon saying that an ounce of prevention is worth a pound of cure. This saying has great value in fishhealth management. Preventive measures have always big advantage over curative practices. If youprevent the disease outbreak you have virtually no loss, but if you want to cure the outbreak you willalways have some losses before you treat and cure them. Moreover, the drug may not provide remediesunder all circumstances. Also, the drug may not help the host survive the infection until the environmentis improved (Kumar et al., 1982). Details about the disease prevention measures and prophylactictreatments have already been discussed under Chapter on “ Fish health monitoring”. Ideally, theaquaculturists should strive to decrease the stress causing factors, eliminate and prevent the entry ofpathogenic organisms, etc., by strictly adhering to the fish health monitoring programme.

10.8.2 Common diseases

All the Asiatic carp species cultured under composite fish culture undrainable ponds are prone to manycommunicable and non-communicable diseases, the most significant among them are described hereunder four groups:

10.8.2.1 Microbial diseases

About one-third of the economically important fish in the world perish every year through disease andabout 60% of these losses are due to microbial pathogens. Virus, bacteria and fungal pathogens comeunder this category.

Viral diseases - As far as carp species are concerned, mainly two viral diseases are of importance.

Spring viremia of carp (SVC): Spring viremia of carp is an acute systemic viral infection caused byRhabdovirus carpio (RVC). The disease was known as “ Infectious dropsy of carps ” till the isolation of thevirus by Fijan et al., (1971), from common carp (Cyprinus carpio). Fijan (1972) subsequently separatedthe dropsical syndrome into spring viremia of carp (SVC), a condition caused by Rhabdovirus carpio andCarp Erythrodermatitis (CE), a condition caused by bacterial agent. RVC is pathogenic to all ages ofcommon carp and perhaps to other cyprinids (Ahne, 1981). The main clinical signs are gathering of fishat water outflows, dark colouration, lower respiratory rate, haemorrhages especially over the skin andgills, loss of balance, exophthalmia, inflamed vent, etc. Internally they show haemorrhages in the viscera,airbladder, etc. Frequently there is secondary invasion of the tissues by aeromonads and pseudomonadsfrom the intestine resulting in the bacterial septicaemia. Peritonitis with serious haemorrhage is normallypresent in acute cases. The virus is shed through faeces and possibly urine. Blood sucking parasitesPiscicola qeoimetra and Arqulus foliaceus have been found to be vectors.

There is no method of eliminating the virus from the infected fish and under no circumstances shouldsuch fish be used for breeding purposes.

Rhabdovirus diseases of grass carp: A new serotype of rhabdovirus similar to spring viremia ofcarp virus (SVCV) and Rhabdovirus carpio (RVC) has been isolated from grass carp (Ahne, 1975) whichcauses large-scale mortality exhibiting more or less similar symptoms like SVC disease such as ventralhaemorrhagic inflammation, bleeding in the scale bases, necrotic fins, inflammation of the alimentarycanal, serious liquid deposition in the abdominal cavity, swollen spleen, pale liver, opacity of the innerwall of the swimbladder with haemorrhages, etc.

Control methods for viral diseases are restricted as there is no chemotherapeutic measures available atpresent. Application of antibiotics helps only in prevention of secondary infections. All the measures aredirected towards avoidance of the pathogen and propagation of pathogen-free brood stocks. Avoidancerequires that sources of virus be detected and the agents identified. In some countries virus-free broodstock are maintained and propagated. In most of the European countries where SVC poses a bigproblem large-scale vaccination of the stock is undertaken which has lowered the losses to a greaterextent. There is also strong evidence that SVC is strainspecific and hence the major outbreak isconcentrated in Europe. There are some other disease conditions of common carp suspected to be ofviral origin which are yet to be investigated in detail.

Bacterial diseases: Among infectious diseases the role of bacteria has been strongly emphasized asthey present many practical problems in nursery, rearing and stocking ponds. They have becomeincreasingly apparent during the last few years and are of serious concern to fish farmers. The actual roleof these micro-organisms vary from that of primary pathogen to an opportunist secondary invader. Someof these bacterial diseases, if remained unchecked, have the potential of wiping out entire populations.Although a number of pathogenic bacteria have been isolated from diseased fishes cultured inundrainable ponds (Kumar, Sinha and Farkas (MS), the following are worth mentioning.

Columnaris disease: The causative agent of columnaris disease is a Gram negative bacteriumFlexibacter columnaris that moves by a creeping or flexing action. Columnaris disease is commonlyoccurring throughout the world and affects virtually all species of freshwater fishes. The disease beginsas an external infection with lesions appearing on the body surface and gills. The type of lesion varies

with the fish species, and as the disease progresses, lesions spread and may cover most of the body. Inrohu (Labeo rohita) the necrotic lesions begin at the outer margin of the fins and spread towards the body(Kumar et al., 1986).

Whitish ulcerations and haemorrhages may also be observed. Bacteria apparently gain entrance to thedermal tissues as a result of injury, multiply in the connective tissue and reach the musculature wherethey form red ulcerations. Erosion of the gill lamellae may also be observed. Diagnosis of columnarisdisease in fish is usually based on the presence of the bacterium in typical external lesions on the body.

Outbreaks of columnaris appear to be related to unfavourable environmental conditions such as lowoxygen levels and accumulations of metabolic byproducts (Meyer, 1968). The stress of crowding(Wedmeyer, 1974), handling (Kumar et al., 1986) or holding them at above normal temperatures as wellas the stress of external injury, facilitate the transmission and outbreak of the disease.

Environmental improvements, especially increased oxygenation, control of organic addition, etc., are themost valuable supportive therapy. Practical control of outbreaks of columnaris is possible with a numberof drugs, including copper sulphate (0.5–1.0 ppm) and potassium permanganate (2–3 ppm) in pondtreatment.

Various other treatments are also employed including dip treatment for 1–2 minutes in 1:2 000 coppersulphate colution. If the fish are able to feed, incorporation of oxytetracycline in the feed at the rate of 8g/100 kg of fish/day for 10 days is also effective.

It should be noted that fish may harbour cutaneous lesions, systemic infections or both. As long as thedisease is confined to ;external lesions, control can be successfully achieved, but once the infection hasbecome systemic the disease is usually fatal.

Bacterial haemorrhagic septicaemia is used to designate septicaemic diseases caused byAeromonas hydrophila and Pseudomonas fluorescens in carp and other species.

Aeromonas hydrophila (organisms previously described as A. punctata and A. liquefaciens) is a gram-negative bacillus, ubiquitous in nature occurring in water column and top sediment of most freshwaterponds. It affects most of the cold-blooded aquatic vertebrates including Asiatic carp species and causesacute and fatal septicaemias, which may be accompanied by external abscesses, ulcers, exophthalmiaand abdominal distensions (Figure 43). Aeromonad infection is usually associated with concomitantenvironmental stress, especially high temperature and/or overcrowding.

Infectious dropsy condition among cultured major carps in India is the most common example. Thecausative agent is a species of Aeromonas and by inoculating a pure culture of the isolate the diseasehas been experimentally produced in fingerlings of catla (Catla catla), rohu (Labeo rohita) and mrigal(Cirrhinus mrigala) (Gopalkrishnan, 1961). Recently, several cases of dropsy condition in catla caused bymixed infection of Aeromonas hydrophila and myxosporidian species has been described (Kumar, Mishraand Dey, 1983). Toor, Sehgal and Sehder (1983) have also observed haemorrhagic septicaemia incommon carp and rohu caused by heavy infection of Aeromonas sp. and the fungus, Saproleqnia sp.

In some cases the disease, caused by aeromonads in catla was restricted to the eye. However, in acutecases the brain and optic nerves were found to be affected (Gopalkrishnan, 1961). The disease wasfound to be seasonal in nature with maximum intensity during the month of October, November andDecember. Similar septicaemiasis have also been reported in silver carp (Hypophthalmichthys molitrix)caused by Pseudomonas fluorescens and Aeromonas hydrophila (Kumar and Dey, 1985).

Pond treatment with potassium permanganate (2–3 ppm) followed by addition of oxytetracycline withfeeds at the rate of 70–80 mg/kg fish/day for 10 days are the most effective and practical measures.Although most treatments are generally ineffective, certain water additives during the transport orhandling of fish are helpful. Acriflavin was found very effective for such purposes when used at the rate of3–10 ppm.

Carp erythrodermatitis: This disease (CE) is probably the most widespread disease of carp inEuropean ponds. Skin inflammation is followed by exophthalmia, oedema of all organs and finallyanaemia. The causative agent is the Aeromonas salmonicida complex. For the control and treatment of

CE, chemotherapeutics are applied as bath, intraperitoneal injection or with food. Oxytetracycline at therate of 7.0–8.0 g/100 kg of fish/day for 8–10 days, oxytetracycline or chloramphenicol or furazolidone inbaths (80–200 g/m3) or oxytetracycline or chloramphenicol as intraperitoneal injections at the rate of 10–30 mg/kg have been found to be very effective (Fijan, 1976).

Figure 43A. Aeromonad septicaemia in rohu (Labeo rohita)

Figure 43B. Aeromonad septicaemia in catla (Catla catla)

Bacterial gill disease: Recently gill hyperplasia syndrome has been detected most frequently incommon carp fry and fingerlings causing retarded growth and poor survival. Myxobacterial complex havebeen found in the affected gills causing hyperplasia (Fig. 44). The disease is found to be widespread andinfectious in nature. Common carp is observed to be more susceptible than other Asiatic carp species.Short baths for 5–10 minutes in 3% common salt solution has been found to be more effective thantreatment with antibiotics. Two subsequent treatments after an interval of one week completely cures thedisease (Kumar et al..,1986).

Fungal diseases: Fungal fish diseases also sometimes cause extensive losses. Species of the generaSaproleqnia sp., Branchiomyces sp. and Achlya sp. are usually implicated in fungal infections, but theyare considered to be secondary invaders following physical or physiological injury brought about by roughhandling or attack by primary pathogens. The ubiquitous fungus, Saprolegnia sp. can affect a wide rangeof fish species including most of the carp species, especially the brood stock, during the postspawningperiod. Initially it appears as white mats over the skin which gradually spread and invade the deepertissues causing mortality. All the stages including the eggs are attacked. Branchiomyces sp. is anotherfilamentous fungus which obstruct the blood vessels in the gill filaments causing discolouration and finallydropping off altogether leaving the cartilaginous support exposed. Malachite green (zinc free grade),formalin, potassium permanganate, copper sulphate, salt, etc., are the common therapeutics for effectiveuse. Malachite green at the rate of 0.1 ppm for pond treatment, 1% solution as a swab and 65 ppmconcentration as short bath/dip for 30 seconds are used. Copper sulphate may be used for pondtreatment at the rate of 0.5 to 1.0 ppm depending on total alkalinity.

10.8.2.2 Parasitic diseases

Parasitic diseases are usually encountered more frequently than microbial diseases. The presence ofhigh level of organic matters in undrainable ponds, encourages multiplication of parasite organisms andresulting in extensive parasitic infection.

Protozoan diseases are among the most significant of all parasitic diseases in carps. The followingare the most important protoizoans parasitizing carp species in undrainable pond culture system.

Ichthyophthirius multifilis: “Ich” or white spot disease is probably one of the most detrimental diseasescaused by this parasite which affects all the species of Indian major carps and Chinese carps as well.The most common symptom is the presence of pinhead size white spots on the skin, fins and gills (Fig.45). It causes simple hyperplasia of the epidermal cells around the site of infection forming blisters. “Ich”is a ciliate protozoan parasite characterized by its relatively larger and horseshoe shaped nucleus inadults and large trophozoites. Incidence of large-scale mortality due to this infection is common innursery and rearing ponds.

Figure 44A. Gill Section of Major Carp showing Normal Structure (H & E Stained)

Figure 44B. Gill Section of Major Carp showing Lamellar Hyperplasia due to Bacterial Gill Disease (H & EStained)

Figure 45. Ich Disease Ichthyophthirius multifilis)

Trichodina sp.: Trichodina is another small saucer-shaped protozoan parasite that harbours gills andbody surface of the host fish. Excess mucous secretion is a common symptom of this disease. Epizooticsare usually encountered in nursery and rearing ponds associated with poor water quality and highstocking density.

Ichthyobodo sp.: A small flagellate external protozoan parasite of skin and gills causes considerabledamage in fry and small fingerlings. It is an oval or kidney-shaped organism which produces severeirritation with excessive mucous secretion causing patches over the body.

Treatments for this group of parasites are varied and many are successful. Pond treatments with 15–25ppm formalin have yielded excellent results. However, if a pond has dense plankton population, suddendeath and decay due to formalin application may cause oxygen depletion. Mixed treatment of malachitegreen and formalin is most effective against “Ich” disease. Pond treatment with 0.1 ppm malachite greenand 25 ppm formalin gives a better result against Trichodina sp., Costia sp. and Ichthyophthirius sp. For“Ich” disease three applications of the therapeutic mixture on alternate days are essential (Leuteux andMeyer, 1972). Some other chemicals such as copper sulphate, sodium chloride, methylene blue, etc., canalso be used.

Myxosporidian and microsporidian species: Myxosporidian and microsporidian parasiticinfections are very frequent in major carp species. Reports of large-scale mortalities of fry and fingerlingsof carp species are common due to such infections. Several species of Myxosporidia have been found toinfect all the carp species and form cysts on the body surface, fins, gills and internal organs such as thekidney and spleen (Fig. 46). However, when large numbers of oocysts are present on the gills, breathingof the fish is adversely affected (Dey, Kumar and Mishra, 1986). Renal infections lead to the damage ofmost of the renal tubules in the form of vacuolar degeneration of the tubular epithelial cells (Mishra et al.,1982). Microsporidian infections are most common in catla among Indian major carps. The parasiteharbours the intracellular spaces of the epithelial cells of the renal tubules (Dey and Kumar, 1985). Themost common symptoms of the disease are weakness, emaciation, scale protrusion, loss of scales,abnormal pigmentation and presence of parasites in renal tubular epithelial cells.

There is no known effective treatment against myxosporodiosis and microsporodiosis. Spores released

from the infected and dead fishes remain viable for quite a long period in the pond bottom before theyinfect new hosts. Infected fish should immediately be removed and, if possible, the pond shouldimmediately be dried and disinfected. In undrainable ponds where drying is not at all possible, the pondshould be disinfected with chlorinated lime.

Worm diseases are caused by trematodes, cestodes and leeches. Many of these parasites do notapparently cause much harm to carp species in undrainable ponds. However, some have been known tobe of serious concern. Among monogenetic trematodes, Gyrodactylus sp. and Dactyloqyrus sp. are mostimportant as sometimes they cause extensive damage. Gyrodactylus infects skin and gills, whereasDactyloqyrus effects only the gills. Carp fry and early fingerlings up to 3–4 g are more prone to thisinfection, sometimes resulting in heavy mortality. Excessive mucous secretions, decolouration of bodyand dropping of scales are the diagnostic features.

Treatment with 25 ppm formalin in ponds or 250 ppm formalin for 1 h bath usually controls themonogenetic trematode infections. Other compounds which may be used include potassiumpermanganate at the rate of 5 ppm or potassium dichromate at the rate of 20 ppm. Bath in 3% sodiumchloride solution till the fish start showing distress is also an effective control measure.

Black spot disease is a frequently occurring disease in nursery and rearing ponds causing extensivedamages at times. The disease is caused by posthodiplostomum and appearance of black pigmentedarea on the skin around the cysts of metacercariae is the common symptom (Fig. 47). Molluscs act as theintermediate hosts and hence eradicating molluscan population and clearance of weed are the two stepsfor controlling the disease. Pond treatment with bleaching powder, copper sulphate or malathion at usualdoses kills the free living stages of the parasite/mollusc population.

Several genera of cestodes have been found to infect major carp species, apparently causing little harm.Brothiocephalus sp. for example is becoming an important menace in nursery and rearing ponds in manyEuropean countries. Another important member of this group of fish parasites is Liqula intestinalis. Itcauses abdominal distension and in advanced cases it may cause rupture of the abdominal wall.

Crustacean diseases: Two crustacean parasites are most widespread and commonly foundparasitizing major carp species sometimes causing large-scale damage in nursery, rearing and stockingponds. These are Lernaea sp. or anchor worm and Arqulus sp. or fish louse.

Lernaea sp.: It has a slender, wormlike body with the head embedded in the flesh of the fish whichcauses unsightly lesions (Fig. 48). The embedded head bears branching processes that resemble ananchor and hence the name anchor worm. Early infections may cause the fish to swim about erratically;in the later stages it causes haemorrhagic and ulcerated areas at the point of penetration. Main injuriesare caused by loss of blood and openings in the skin which allow entry of secondary pathogens. Lernaeamay be found at the bases of fins or scattered about the body surface.

Figure 46. Myxogoan cysts on gill

Figure 47. Black Spot Disease in Fry/Fingerlings of Indian Major Carp

Figure 48. Common Crustacean Parasites

Arqulus sp. infection is widespread and frequently appears in undrainable ponds. Sometimes it causesserious problems resulting in high mortality. They are large copepods and consequently they areconspicuous objects on the fish that they inhabit. Fish with advanced infestations are characterized byerratic swimming, restlessness, haemorrhagic areas and lesions over the body with attached parasites.The parasite is easily recognised by flat, leaf-like carapace with emerging appendages (Fig. 48). Althougha number of therapeutics have been recommended for the control of Lernaea sp. and Arqulus sp.infections, including potassium permanganate and sodium chloride, they have been found to be of partialsuccess in field conditions. Malathion is an easily available organophosphate having relatively low toxicityto humans and has been found to be very effective in controlling copepod parasitic infections when

applied at the rate of 0.25 ppm. Two subsequent treatments at the interval of one week completelyeradicate the parasite.

10.8.2.3 Environmental and nutritional diseases

Diseases known to be occurring due to nutritional deficiencies and environmental disorders are of littleimportance. Proper monitoring and management of pond ecosystem and provision of adequate quality ofsupplementary feed will avoid occurrence of such diseases which sometimes appear in ill-managedponds. Liver lipoid disease (LLD) in catla and gas bubble disease in early fry of rohu are worthmentioning.

10.8.3 Therapy of fish diseases

10.8.3.1 General considerations

Four key factors are of utmost importance whenever a chemical application is contemplated (Meyer andWarren, 1975). They are the water, the fish, the causative agent and the chemical. Complete informationabout each of these factors must be in hand before any therapy is planned. Knowledge concerning thefish includes the species affected and unaffected, the number and size of the fish and their specificrequirements. Information about the causative agent is based upon correct diagnosis and the vulnerablestages in its life cycle. Data about the pond water temperature, pH, alkalinity, dissolved oxygen, totalwater volume, etc., are also required for the selection of the most suitable drug. When all of the foregoingdata are in hand, one may then begin to consider which drug or chemical should be used. Selection ofthe therapeutic compound must be based on the following considerations:

effectiveness against the causative agent;

adverse effects, if any, on the host;

possibility of penetrating the site of infection;

effectiveness under the existing water chemistry;

local availability;

cost considerations;

convenience of application.

It is reemphasized that the success of therapy depends very much on the correct diagnosis of theproblem. Moreover, it should also be considered that disease outbreak is the indication of more basicenvironmental problems and hence such problems should also be identified and corrective measurestaken.

10.8.3.2 Methods of therapeutic application

Therapy can be applied in two ways:

external treatments;

treatment via diet;

External treatments: There are two methods of application of external treatments.

Immersion in chemical solution: The most common method of administering therapeutic agents to fish isimmersion in water soluble compounds (Fig. 49). Depending on the available facilities, severity andnature of the disease and local conditions, three types of immersion treatments are suitable forundrainable pond culture situations. These are baths in lower concentration of chemicals ranging fromshort to prolonged periods and dips where the fish are dipped into a chemical solution of highconcentration for a very short period ranging from a few seconds to 5 minutes. Indefinite bath is suitablefor pond treatment where the chemical is applied at a low concentration for an indefinite period and the

chemical is allowed to gradually dissipate or detoxify naturally.

Figure 49. Treatment of Fish by Immersion in Tnerapetic Solution

Swabs: Swabbing is application of drugs in high concentration when dealing with individual fish withlocalized external infections. For better convenience it is desirable to immobilize the big-sized fish prior toswab application.

Treatment via diet: This method is usually applied for treating the systemic bacterial diseases or gutparasites by incorporation of the drug into the feed. Loss of appetite is one of the first signs of a diseaseand hence in such cases the use of drugs in proper doses through supplementary feeding becomesdifficult. Leeching of drug is another problem. If some of the water soluble drugs are properly mixed withvegetable oil prior to its final mixing with the feed, such losses may be minimised. Generally, feedingmedicated feed is considered to be a prophylactic rather than a therapeutic measure.



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11. HARVESTINGGrowth rate of the fish, market demand, desired market size, availability of seed and pond condition, arethe major considerations for deciding on the time of harvesting. Harvesting the fish stock should bestarted before the “Law of diminishing returns” starts operating, i.e. the rate of growth of the fish for theinvested inputs such as feed and fertilizers start declining. This happens mainly because the growth rateof fish is not linear. Further, the biogenic capacity of the pond, i.e. capacity of water for providing food andoxygen for the fish, cannot be increased after a certain stage according to the need of the increasing fishbiomass.

11.1 Harvesting in nursery ponds

In nursery ponds the fry usually grow to a size of 25–35 mm in about a fortnight with more than 70–80%survival, when they become ready for harvesting. Harvesting should be done by seining the pond waterusing a close meshed (1.45 mm) drag net. Several netting operations should be done to ensure neartotal harvesting of the stock. No harvesting should be done on a bright sunny day or in cloudy weather asthere might be heavy mortality of tender fry due to high temperature related increased metabolism andthe depletion in available dissolved oxygen. The most suitable time for harvesting is the early hours of themorning. Feeding should be stopped a day before harvesting to minimise the conditioning time requiredfor transporting fry over long distances.

11.2 Harvesting in rearing ponds

Harvesting of fingerlings should be done after three months of rearing when they attain the desired sizeof 100–150 mm. However, in some cases fingerlings are to be kept for a prolonged period for marketingduring the period of scarcity of seed to fetch better price. Harvesting should be done by seining the pondusing a drag net of about 8.0 mm mesh. However, complete harvesting of all the species, especially thebottom feeders is usually difficult and hence several netting should be done to ensure near totalharvesting. A modified form of net which is described below is very effective in catching all the species ofcarps even in rearing ponds. Feeding should be stopped a day prior to harvesting.

11.3 Harvesting in qrow-out ponds

11.3.1 Complete harvesting

Usually the carp species attain marketable size within one year and hence the shorter rearing period ofless than a year is not recommended unless there is an exceptional threat of flood or outbreak of disease,or for financial reasons. In some exceptional situations when the pond is of a seasonal nature retainingwater hardly for 6–7 months, and also in cases where the pond is prone to serious flooding, the rearingperiod should be synchronised accordingly. Post-flood stocking and pre-flood harvesting should be donein flood prone ponds while in seasonal ponds harvesting should be done before the water level fallsbelow the critical level. Usually these cultivated fish species do not grow well in winter months. Hence inagroclimatic zones having severe winter months the stocking and harvesting phases should be adjustedso as to have complete harvesting before the onset of winter. In regions where seeds of desiredcultivated species are available only during post-monsoon period, i.e. October/November, the stockingshould normally be done during this period and the crop should be harvested by next October.

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11.3.2 Partial harvesting

It has been experienced that even under the best management, Indian major carps on an average attainhardly 1 kg in size in a year, while Chinese carps reach over 2 kg or so. This kind of differential growthcomplicates the final harvesting programme and hence in such areas partial harvesting of marketablesize fish should be carried out. However, while harvesting, interrelationship of the species cultured shouldalso be seriously considered. Bottom feeders like common carp and mrigal partly subsist on the faecalmatter of grass carp and hence an unplanned removal of grass carp may affect the growth of thesespecies. On the other hand, removal of only bottom feeders may create some ecological problems.

Further, the market price of fish is directly related to its size. This factor should also be considered beforedeciding on the harvesting programme.

Possibility of partial harvesting very much depends on the availability of fingerlings of desired carpspecies. In such cases the fish already reached the marketable size should be harvested and the stockshould be replenished. Usually fish over 500 g should be harvested every 3–4 months with simultaneousstocking with fingerlings. Such partial harvesting programme should be synchronised with peak marketdemands depending on seasons, festivals, etc.

11.4 Application of proper gear

Harvesting of fish in undrainable ponds should be done by seining the entire pond using desired size ofdrag net. However, in larger water bodies and especially for partial harvesting, cast nets and gill nets toocan be effectively employed. It has been observed that by three subsequent operations of simple net ofdragging type, about 90% of the surface and column fishes are caught, whereas the catch of bottomdwellers fall in the range of 20–40% of their entire population. A new gear has been designed by Rout,Lakshmanan and Kanaujia (1979) which can be operated in rearing and stocking ponds with increasedefficiency and significant reduction of manpower.

The net is prepared by joining net pieces of 15 × 5 m with 8 mm mesh for fingerlings and 25 mm barmesh for large sized fish. The free bottom part of the net is provided with a nylon twine (3.0 mm) withsinkers and passed through the bottom series of meshes. The free end of the net is then turned over tothe main net and attached at equal intervals to a second line of nylon twine which functions as a falsefoot rope. This results in the formation of pockets of 20 × 30 cm. Metal sinkers are tied to the first footrope in each pocket to keep the mouths of the pockets open and also help the net sink in the bottom silt.The net is provided with a strong head rope with polythene floats (Fig. 50).

11.5 Precautions

Weed infestation if any should be removed before harvesting.

All the anti-poaching devices kept in the pond should be removed before netting.

Feeding should be stopped 2–3 days before harvesting.

Harvesting should be done during cool, clear weather and time should be adjusted according to themarket hours.

Proper care and prophylactic measures should be taken before releasing back the potentialbreeders.

Harvested fish should always be kept under proper shade after washing.



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12. TRANSPORT AND MARKETINGImmediate disposal of farm products in perfect condition adds to the overall farm income and reputation.Fry, fingerlings and table size fish are the main products of undrainable ponds which require differentways and means of disposal. Table-size fish after harvesting need immediate transportation so that itmay reach the destination in fresh condition whereas fry and fingerlings are to be transported in livecondition.

12.1 Transport of fresh fish

Fish perish more quickly than chicken, beef, pork, etc., and the spoilage is mainly due to combined effectof autolytic and bacterial decomposition which is rapid in tropical climate. The following proceduresshould be adopted to keep the fish in good condition.

Figure 50. Modified Net with Measurement Detail

The moment the fish is harvested, they should be kept under shade and washed properly withclean water to remove the bacteria adhered to the surface of the body and the gills.

Gills and gut should be completely removed if there is no objection from consumers. Generally,colour of the gill is an indication of freshness.

Cleaned fish should be given a one minute dip in 0.2% sodium nitrate solution.

Cover the fish with layers of a mixture of ice and salt.

Cover with wet bags or clothes and transport it at once.

12.2 Transport of live fish

For safe delivery of live fry, fingerlings and brood fish to destinations, two systems are presently in use:the open system for short distance and the closed system for short and long distance transport.

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12.2.1 Conditioning and preparation for transport

This involves starving the fish prior to harvesting and keeping them in overcrowded condition foremptying their gut and to make them accustomed to the conditions of transport. Artificial feeding thereforeshould be stopped 1–2 days before harvesting. Although a number of containers and enclosures can beused for conditioning, the most common is the hapa made out of cotton or nylon mosquito netting materialfixed in the pond or in a still water section of a stream or river, but always in shaded areas. After netting,the fry and fingerlings are transferred to the conditioning hapa (Fig. 51) and kept for about 6 h withcontinuous and vigorous splashing of water from all sides of the hapa. Conditioning time depends on thedistance to be covered and the anticipated time of confinement during transport. During this period theypass their remaining excreta and the gut becomes almost empty. The optimum temperature forconditioning carps is around 26–29°C. In the case of brood fish the application of supplementary feedshould be stopped 2 days before the proposed date for transportation. Handling during netting andtransport should not be allowed. Conditioning of brood fish in hapas is not required. Risk of outbreak ofdiseases becomes high due to the stress created during transport and hence the use of antibiotics isrecommended.

12.2.2. Open system of transport

This is the traditional system of transport where fish seed materials are transported in open containers.These containers were earlier in the form of earthen hundies which have now been replaced byaluminium vessels of about 25–40 1 capacity (Fig. 52). Water is filled up to two-thirds of the total capacityof the vessel to transport about 1 000–5 000 early fry (12–15 mm) depending on the anticipated period oftransport. Such vessels are normally carried manually or by train. When they are carried manually, arhythmic jerky movement is created which keeps the water well aerated. Dead ones are periodicallyremoved with the help of a piece of cloth and the water is changed partially but frequently during longdistance transport. Earthen hundies help to keep the water cool, but due to high risk of breakage they arenow going out of use. Bigger galvanised steel containers of about 50 to 200 1 capacity sometimesmounted on a thermal insulated base of wood or other materials are also in use for transport of fry andfingerlings for short distances. In the case of fingerlings or advanced fry transport, the mouth of thecontainer is always kept covered with cotton or nylon mosquito netting material. The ever increasingdemand for carp seed has created a great impact upon village level seed production activities in recenttimes. Farmers are now taking up induced breeding of carps and the seed are now being reared in theirbackyard or ponds. This method of open system of live seed transport for short distances is of significantrelevance for localised marketing scattered throughout the region, in spite of its many limitations.

Figure 51. Conditioning Hapa

Figure 52. Aluminium Containers (Hundies) for Transporting Fish Seed

Plastic pools and canvas bags with varying degrees of capacity are also used for transport offry/fingerlings and brood fish under open transport system. These are mounted over bicycle, motor van,tractor trailer, etc., and used for short distance transport.

Relatively bigger truck mounted open tanks are also in use with or without facilities for mechanicalaeration and/or water circulation. Such tanks are used in organised fish seed marketing sector. Tanksvary in size but usually 3–4 tanks are accommodated on a truck. Fry, fingerlings and brood fish areusually transported up to distances covered within 3–4 hours with ease. Tanks are covered with wet clothand some persons are employed for continuous but gentle splashing of water. Improvements have beenmade and now plastic cushioned lining is provided to the tank for avoiding physical injuries. Some sort ofaeration or water circulation is provided by a pump during transportation. Such a system offers safetransport of live fish upto a distance of about 500 km with mortality as low as 5%.

12.2.3 Closed system of transport

For transporting live fish and fish seed over exceedingly long distances and from one country to another,closed system of transport is most suitable. In this system of transport live fish/seed materials are packedin closed containers with oxygen under pressure with airtight seals. Polythelene or vinyl chloride or otherplastic bags of various capacities ranging from 15–35 1 are in use. These bags can be purchased readymade from the market or, if needed in larger quantity, can be made from cylindrical rolls. Widely used sizeis 47 cm × 46 cm which can be accommodated in 18 1 capacity biscuit tins after being filled with water upto one-third of its capacity. The water for such use should be clean and preferably from a tube well.Number of seed materials to be packed per bag vary according to their size and expected duration oftransport (Table 40).

Table 40Packing density of fry/fingerlings of Indian major carps

for 12 h journey in 16–18 1 capacity plastic bags(Mammen, 1962)

Seed size (cm) No. of seed (Range) No. of seed (Average)1 1 000 – 10 000 5 500

2 500 – 5 000 2 2003 200 – 1 000 6004 200 – 500 3305 75 – 300 2256 50 – 200 807 25 – 100 708 25 – 50 40

After putting the required number of fish seed in the plastic bag containing water, oxygen is pumped intothe water until it is saturated. The bag is then partially blown up with oxygen and tied with a leak proofknot.

These plastic bags are individually packed in cardboard, metal or wooden boxes to prevent any damageto the bags during transport. Biscuit or oil cannisters of 18 1 capacity are widely used for such purpose. Itmust always be kept in mind that the live fish packets should not be exposed to temperature over 30°C.Best results are obtained when it is kept between 20–28°C.

A simplified method suited to rural condition has been developed for fish seed transport in a closedsystem where instead of oxygen, a cycle pump is used to pump atmospheric air into the plastic bagscontaining fry in 6 1 of water. It has been observed that 500 mrigal fry (26–35 mm) can be safely keptalive for a period of 24 h with 1% mortality. At 300 fry/6 1 of water the fry survived for a period of 96 hwithout any mortality (Selvaraj, Mohanty and Ghosh, 1981).

Brood fish are also transported in some larger closed containers mounted on wheels and pulled by jeepor a tractor. The modified splashless live fish carrier (Mammen, 1962) is useful for transporting brood fishas well as fingerlings. This is a tanker having a capacity of 1 150 1 with lining of synthetic padding,autoclave type airtight lid and a built-in aeration system which works by the engine of the transportingvehicle using belt transmission. An oxygen cylinder is also kept on the carrier as a standby for emergencyuse.

A total weight of 250 kg of live fish can be transported in such a tank. About 90 000 carp fingerlings withfish to water ratio of 1 kg to 4.5 1 of water have been successfully transported to distant places.

A bio-gas-plant type of live fish carrier has also been designed by Patro (1968) which consists of anouter lower circular chamber of about 1.2 m diameter opening at the top to which is fitted the upperinverted one of slightly smaller dimension. The top of the inner chamber is closed and, provided with avalve and air vent. The outer lower chamber serves as a storage tank which is filled with water along withthe fish to be transported while the inner chamber serves as an oxygen reservoir under pressure. It cantransport 100 kg of fish at a time safely up to 5 h, thereafter refilling of oxygen becomes essential (Fig.53).

Figure 53. Live Fish Carrier

12.2.4 Drugs and chemical aids

Production of toxic gases such as ammonia and excess amount of carbon dioxide as metabolic wasteproducts are the main causes of stress condition and mortality of fish in undrainable ponds. Drugs andchemicals are used to reduce the metabolic rate, thus cutting down the production rate of ammonia andcarbon dioxide. Such situations reduce the stress effects. Under stress conditions fish become moreprone to attack by pathogenic bacteria. Use of antibiotics and some other fish therapeutics help inreducing such risks. Some of the easily available fish anaesthetics such as Novocaine at the rate of 50mg/ kg of fish, barbital sodium at the rate of 50 mg/kg of fish, tertiary amyl alcohol at the rate of 2 mg/4.51 can be used for anaesthetizing the fish to be transported. Ms 222 is also a common tranquilizer whichcan be used for anaesthetizing brood fish in a 1:10 000 to 1:30 000 solution for 15 to 20 minutes.Carbonic acid has been found to be useful in fish seed transport. A concentration of 500 ppm of carbonicacid in the transport medium itself was found to be optimum for rohu fry under oxygen packed transport(Mishra, Kumar and Mishra, 1983).

Important operational steps:

stop feeding 1–2 days prior to transport;

condition under shade up to 6 h before packing;

use tube well or chlorine free tap water or clear pond or river water;

select only healthy and vigorous fry/fingerlings;

plastic bags should be checked before and after oxygen packing to check any possible leak;

carriers of fish/seed containers should be covered to avoid strong sunlight;

when resting during the journey carriers should be parked under shade;

if atmospheric temperature is high, occasionally sprinkle cool water over the metalic containers tobring down the temperature;

before releasing, the bags or hundies should be floated in the water where the seed are to bereleased at least for 10–15 minutes to equalise the temperature;

slowly mix the pond water and gradually release the fish;

if anaesthetic is used, prior trials should be made as the doses vary with the water quality and thespecies of fish.

12.3 Marketing

Most of the major cities and fish sale depots are far away from the rural fish production centres. In suchsituations marketing involves offering the products in proper form, time and place desired by theconsumers. In fact, product marketing of any production system is the core activity upon which the futureof the industry depends considerably. In case of fish production system, marketing assumes relativelygreater importance because of the highly perishable nature of the product. In addition to fish, fish seedmaterials - spawn, fry and fingerlings - are also important products of pond fish culture, but theseproducts are used by the industry itself.

12.3.1 Market potential

There are areas that have a higher per caput production and also there is a regional variation inconsumption pattern. Proper marketing strategy is needed to stabilize such imbalances in the largerinterest of the producers and consumers. In some of the eastern states of India, especially in WestBengal and in countries like Bangladesh, freshwater carps are in maximum demand where 70–80% ofthe population are fish eaters. In some southern states, especially in Andhra Pradesh where freshwateraquaculture is emerging as an industry, the local preference for carp species is relatively less and hencethe surplus is marketed to West Bengal. Calcutta markets in West Bengal receive about 30 000 t of fishper annum from other states of India. The existing price of freshwater carp in West Bengal is around US$3.0/kg compared to an average price level of US$ 1.5–2.0 in other states indicating the demand andsupply gap.

The fish seed production/demand picture is just the reverse. West Bengal is a surplus state whichproduces maximum quantity of fish seed through controlled breeding and supplies to other states inIndia.

12.3.2 Marketing of table size fish

Marketing functions or services include many aspects such as collecting small quantities from manyproducers, grading, packing, transporting to distant city based wholesale markets, and distributing toretailers.

The term “ middlemen ” is often used to describe a wide variety cf collectors, agents and distributorsserving as links between the producer and the consumer. Considerable portion of the fish is sold in fresh

condition. In the absence of easy accessibility to the market, fish is sold to the middleman at the farmgate invariably at a much lower price than what it would have fetched in the retail market. Also, fishfarmers who are generally poor, ignorant of market dealings, and financially indebted to money lendersare compelled to sell their produce to the middlemen in fulfillment of the conditions of loan taken for fishculture operation. Generally speaking, the fish traders and middlemen exploit the poor fish farmers.

Out of many market channels, the shortest and best possible channel in the interest of both producer andconsumer is the direct one. But this channel is operative only during special occasions when theconsumers need the fish in bulk for some social and festive celebration. There may be several functionallinks (about 4) between producers and consumers through each market channel and at every link theycharge about 5–20% for their services. Usually the consumers pay about 70–80% more than theproducer's price.

In addition to the seasonal variations in the market price, fish prices increase due to increased demandduring the time of religious and social celebrations. The volume of fish sale is normally at its peak duringMarch/April, mainly due to increased harvesting prior to pre-stocking pond preparation for the next crop.Price variations are also linked with the species and size of fish (Table 41). Prices are also related tostate of freshness of the product. Fresh fish fetches a better price and are in greater demand than icedfish. The current market price of carp species in Orissa markets are given in Table 41 which gives moreor less the general picture of prices in fish markets of Eastern India.

12.3.3 Marketing of fish seed

Until recently, the state fisheries institutions were the major channels for the collection/production anddistribution of fish seed. Due to increased adoption of composite fish culture technique throughout India,severe shortages of fish seed supply have been felt, and to satisfy this growing demand the Governmenttook immediate steps to increase the production of fish seed. Many state and private hatcheries wereestablished during this period and extension services were put into action to promote induced breeding atfarm level. As a result, many small and big seed producers emerged and consequently fish seedmarketing became operational. Within a few years this trade has grown to a considerable size. There aretwo general patterns - the more or less organized one through fish seed syndicates and cooperatives andthe other which is highly localised in operation. Collection of seed from scattered seed production centresand ensuring redistribution of the collection to fish farmers in remote villages is the responsibility of theorganized sector, while a localised marketing system distributes fish seed to nearby villages through localagents. The price of fish seed varies according to size and species. Approximate cost of fish seed of carpspecies in Orissa State is presented in Table 42.

Table 41Current market price of fish in Orissa

Species Retail market price (Approximate) (US $)*

Below 0.5 kg 0.5 - 1.0 kg 1.0 - 2.0 kg Above 2.0 kgCatla 1.5 1.9 2.2 2.5Rohu 1.6 2.0 2.2 2.5Mrigal 1.6 2.0 2.2 2.5Silver carp 1.1 1.5 1.6 1.8Grass carp 1.5 1.9 2.2 2.5Common carp 1.3 1.6 1.7 1.9

* 1 US $ = 15.00 Indian Rupees

Table 42Current price of fish seed (US $)*

Fish seed Catla Rohu Mrigalcarp

Silvercarp Grass carp Common

carpSpawn** 20.8 20.8 28.8 NA NA 20.8

Fry*** (25–30 mm) 16.6 8.3–12.5 8.3–12.5 30.0–30.5 50.00 8.3–12.5

Fingerlings*** (80–120mm)

60.0–70.0

40.0–42.0 40.0–42.0 55.0–65.0 80.0– 40.0-

85.0 40.0–42.0 42.0

* 1US $ = 15.0 Indian Rupees;** Price/100 000;*** Price/1 000; NA = Information not available.



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13. ECONOMICS OF CULTURE OPERATIONSCost of production is more important than the rate of production and it is the cost benefit ratio whichdecides the viability of any production technology. Therefore, it is necessary that undrainable pondculture operations are subjected to economic analysis which would indicate the factors influencing farmprofitability and the way in which these factors of production are to be regulated to maximise net return.Economic analysis of all the three types of undrainable pond culture - raising of fry from spawn, raising offingerlings from fry and raising of table size fish from fingerlings - are considered below.

13.1 Raising of fry

The economics of fry rearing mainly depends on the size to which they are grown (25 mm to 35 mm),costs of inputs, nursery size, species reared and the demands for seed. Sinha and Ranadhir (1980)worked out the detailed economics of fry rearing on the basis of 1979 market price. However, the presentanalysis is based on the 1986 market price. A more generalised case of fry rearing operation in a 0.04 hapond in the region of Orissa has been taken here as an example (Table 43). Although the prevailing costof catla, grass carp and silver carp fry are more than double than that of rohu, mrigal and common carp,the present economic consideration is based on the latter group of carp species. Again the rate ofstocking is also considered at a lower level of 3 million spawn/ha. Normally the crop is ready within 15days, but disposing of fry itself takes about a week.

The net profit is approximately 4 100 US $/ha from each crop of about 3 weeks. Normally 3–4 such cropsare raised from the same water area during the rearing season of the year. The fry of certain other carpspecies such as grass carp, silver carp and catla are in high demand and fetch 2 or 3 times higher price.

13.2 Raising of fingerlings

Fingerlings (100–150 mm) production involves rearing of fry for about 3 months in rearing ponds. Again,the economics of fingerling rearing naturally depends upon the size to which it is grown, its market priceand the cost of material and labour inputs. There is great variation in the market price of the product itselfwhich mainly depends on the size and species of the marketed fingerlings. Large (above 100 mm) andhealthy fingerlings fetch almost double the price of smaller ones. Likewise, fingerlings of grass carp, silvercarp and catla are sold at about double the price of fingerlings of the same size of species like rohu,mrigal and common carp. The economics of fingerling raising in an average rural, undrainable pond of0.08 ha in Orissa State is presented here (Table 44).

Table 43Production cost, output and net income from

0.04 ha nursery ponds (rohu, mrigal and common carp)No. Item Quantity Cost (US $)A. INPUT 1. Weed clearance 1.66 2. Eradication of predatory and weed fishes, using mahua oil cake 100 kg 10.00 3. Organic manure 400 kg 3.33 4. Lime 12 kg 1.50 5. Selective poisoning of larger copepods using malathion 400 ml 2.00

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6. Soap and oil treatment (720 g of soap and 2.25 1 of oil) 6.70 7. Stocking material 0.12 million (spawn) at the rate of 3 million/ha 50.00 8. Supplementary feed 20 kg 2.70 9. Netting charges for nursery preparation and harvesting 8.33 10. Labour for watch and ward, feeding, fertilization, etc., 20 man-days 20.00 11. Pond rental 8.33 12. Maintenance and miscellaneous 10.00 13. Interest on working capital at the rate of 18% (for six months) 11.20 Total input cost 135.75B. RETURN 1. Fry (at an average survival level of 60%); (at the rate of 4.166 US $/1000 fry) 72 000 fry 300.00C.NET PROFIT (B-A) 164.25

The net profit from this 0.08 ha pond corresponds to an income of US $ 2 746.37/crop/ha in about 3months. During the rearing season of the year it may be possible to raise two crops of fingerlings from thesame water body. If the ponds are relatively small and suitable for rearing of spawn to fry stage, initially3–4 crops of fry are raised and finally the ponds are usually utilized for fingerling production.

In relatively bigger ponds, after rearing 2 crops of fingerlings, they are utilized for culturing fish for aboutsix months to an average weight of about 500 g.

Table 44Production cost, output and net income from 0.08 ha rearing pond (rohu, mrigal and common carp)

No. Item Quantity Cost (US$)

1 Weed clearance - 3.32

2 Eradication of predatory and weed fish using mahuaoil cake 200 kg 20.00

3 Organic manure(raw cow dung) 400 kg 3.334 Lime 24 kg 3.005 Inorganic fertilizer: Urea 16 kg 3.35 Triple super phosphate 6.4 kg 1.006 Fry at the rate of 0.25 million/ha 20 000 83.327 Supplementary feed 225 kg 30.378 Netting charges for periodical netting and harvesting 13.33

9 Labour charges for watch and ward, feeding,fertilization, etc. 90 man-days 90.00

10 Pond rental 16.6611 Maintenance and miscellaneous 20.00

12 Interest on working capital at the rate of 18% (for sixmonths) 25.89

Total input cost 313.57B. RETURN

1 Fingerlings (at an average survival level of 80%) 16 000 (at the rate of 33.33 US $/1000fingerlings 533.28

C. NET PROFIT (B-A) 219.71

13.3 Raising of table-size fish

The technology of composite fish culture in undrainable ponds has been successfully demonstrated indifferent agroclimatic regions of the Indian sub-continent at different use of input levels. Based on datacollected from these sources detailed economic evaluations have been made (Sinha, 1978; Sinha andRamachandram 1985; Ranadhir, 1984). The cost analysis presented here is also based on actual casestudies. However, the costs are updated (1986 price) and expressed in U.S. dollars to have better

comparability among three different levels of productions using different levels of inputs. Fish productionrates ranging from over 2 700 kg/ha/yr to over 10 000 kg/ha/yr, have been achieved depending onintensity of input use. Three case studies have been selected to represent high (about 8 000–10 000kg/ha/yr), medium or intermediate (4 000–6 000 kg/ha/yr) and low level (less than 4 000 kg/ha/yr) ofproduction packages. All these three cases have been taken from Jaunpur Centre of the All IndiaCoordinated Research Project on Composite Fish Culture. Table 45 gives the details of material inputsused in actual quantities, while Table 46 gives a summary of costs/benefits of fish culture in undrainableponds. The major difference in terms of input cost is mainly due to feed component, which is maximum inhigh production level while in the low production level it has not been used at all. This shows that thetechnology of fish culture in undrainable ponds offers flexibility to suit fish farmers of varied socio-economic background.

Feed costs constitute 50–60% of the total cost of production of medium and high input technology ofcomposite fish culture. Many small-scale fish farmers do not use much fertilizers, and use very little or nosupplementary feed (Ranadhir, 1986).

Table 45Per hectare inputs/outputs in case studies of three different levels of fish production

No. Input Production levelsHigh Intermediate Low

1 Mahua oil cake 1 071 kg - 1 200 kg2 Organic manure (cowdung) 9 057 kg 10 068 kg 7 500 kg3 Lime 1 786 kg 750 kg 300 kg4 Fertilizer: Ammonium sulphate - 540 kg 396 kg Muriate of potash 46 kg 45 kg 50 kg Urea - - 30 kg5 Feed: Mustard oil cake 8 079 kg 6 072 kg - Rice bran 5 800 kg 2 712 kg -6 Stocking material 5 000 nos. 5 000 nos. 5 000 nos7 Weeds 180 t 75 t 100–150 t Output: Gross production of fish: 6 980 kg 4 794 kg 2 746 kg

Table 46Per hectare costs and benefits of table size fish production

at high, intermediate and low production levels

No. ItemCosts (U.S. $)*

High levelof

production

Intermediatelevel of

production

Low levelof

productionA. INPUTS1 Pond rental (estimated) 208.25 208.25 208.252 Wages (470 man-days, estimated) 470.00 470.00 470.003 Maintenance and repairs (estimated) 250.00 250.00 250.004 Mahua oil cake (for eradicating predatory and weed fishes) 107.10 - 120.005 Organic manure (cowdung) 75.47 83.90 62.506 Lime 223.25 93.75 37.507 Fertilizers: Urea - - 6.28 Ammonium sulphate - 51.75 37.95 Single super phosphat 50.32 27.50 22.00 Muriate of potash 3.83 3.75 4.16

8. Feed: Mustard oil cake 1 683.12 1 265.00 Rice bran 362.50 169.50 -9. Fingerlings 166.65 166.65 166.6510. Weeds 41.66 83.33 83.33 Sub-total: 3 642.15 2 873.38 1 468.62

11 Miscellaneous costs at the rate of 5% of recurrent costs(Items1–10) 182.10 143.66 73.43

12 Interest on working capital at the rate of 18% for 6 months 344.18 271.53 138.78 Total cost 4 168.43 3 288.57 1 680.83B. RETURN 1. Cost of fish at the rate of US$ 1.50/kg 10 470.00 7 191.00 4 119.00C. NET INCOME (B-A) 6 301.57 3 902.43 2 438.17

* US $ = 15.00 Indian rupees



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14. AQUACULTURE EXTENSIONAquaculture contributes significantly to the rural economy of most of the Asian and other developingcountries by providing part- and full-time occupation to the farmers, fishermen and landless agriculturallabourers. India, and other developing countries of the South Asian region are endowed with ample waterresources in the shape of freshwater ponds and tanks for fish culture, but these are not under effectiveand optimum utilization in spite of highly developed available technologies. Research results have shownexcellent production potential as well as economic viability of such technologies, but until thesetechnologies are successfully transferred to the beneficiaries, the desired objective cannot be achieved.Like agriculture, aquaculture is also an agroclimatic-based technology which, when developed in oneagroclimatic region, may need modifications and refinement for adoption to another region. Agricultureextension thus involves not only the extension of aquaculture technology, but also certain levels ofadoptive research in a particular field environment before it is launched for large-scale extension. It is atwo-way education process in which both scientists and farmers contribute, receive and interact with theinvolvement of extension workers as a link between the two and a catalyst as well (model). In otherwords, it is a non-formal adult education programme for educating and training the rural mass to acquiresuitable fish farming skills and capabilities with a view to boosting fish production efficiency and thesocio-economic condition.

14.1 Objective

Aquaculture extension is basically an educational process by means of which scientific and technologicalknowledge of aquaculture is carried to the farmers to upgrade their existing operation and farmmanagement skills. The philosophy behind this process is to change the altitude, enhance the skill andknowledge of the fish farmers to upgrade their aquaculture practice. It also aims at binging maximumpossible unutilized and under-utilized water areas under modern fish culture operation so as to raise thestandard of living of the fish farmers through improving productivity and profitability. Apart from achievingits own target its overall objective is also to signifiantly contribute towards rural development by improvingrural economy, creating additional gainful employment opportunities, fighting malnutrition and preventingrural exodus.

14.2 Launching aquaculture tension programme

Any aquaculture extension programme is designed based upon broad national consideration to achievenational goals and targets viz-a-viz local considerations to achieve short-term objectives such asapplication of composite fish culture in undrainable ponds to improve the aquaculture production level. Alocal aquaculture extension programme is relatively more definite in terms of scope and target. Like anyother aquaculture extension programme, there should be three sequential steps for the dissemination offish culture technology in undrainable ponds. They are as follows:

Programme planning

Programme implementation

Programme evaluation

14.2.1 Programme planning

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While planning the dissemination of fish culture technology one should always bear in mind that theprogramme should be a self-regenerating production endeavour and once it is stimulated should continueon its own with a changed attitude and active participation of the recipient. This involves situation-specificstrategies. The main components of programme planning are pre-adoption survey of the area, situationanalysis, setting programme goals and finally designing strategies in a sequential manner.

Village Survey

Fish culture is basically a rural farming system and hence village survey is the most common method foridentification of the difficulties faced by the farmers and to find out the scope and suitability of a specifictechnology needing to be transferred (Radheysham and Kumar, 1982). The main objective is to get anoverall picture of the village and the villagers, their attitude, values, together with their socio-economicconditions and also to locate and assess the available freshwater resources. It also helps to identify thelocal institutions, village leaders, progressive farmers, school teachers, village level workers in order todesign the most feasible extension strategy and also to establish a permanent rapport to strengthen theextension services. At micro level it provides information about the socio-economic conditions ofindividual fish farmers, the pattern of fish farming, and the technological gap.

The village selected for the survey should be such that it may represent the locality. Regular contact withimportant and progressive farmers of the village should be maintained. They should be informed aboutthe objectives of the survey proposed to be undertaken. Interviews with these persons will provide anoverall picture of available natural and human resources and possible areas for development. Finallydetailed relevant information may be collected from individual pond owners/fish farmers and fishermenthrough personal interviews/questionnaires.

Resource Inventory

Availability of water resources

Various types of water resources are available for fish culture but usually all of them are not fullyutilized. Large, medium and smaller types of water bodies are generally available in villages whichmay be suitable for fish culture. Many small water bodies are found fully shaded by large marginaltrees and thereby lying unproductive. Some unconventional types of water areas with potentialityfor intensive aquaculture are also available. Canal/road and village side small and large ditches,pits emerging due to construction of mud houses etc., are some of the unnoticed and untrappedpotential aquaculture resources suitable for seed production and short-term fish rearing (kumar,mohanly and bhanot). Low-lying and swampy areas which are formed naturally due to humanactivities are also potential sites for undrainable ponds for fish culture.

Availability of human resources

It is a well-known fact that the majority of the people in developing countries live in villages andmost of the rural population depend upon agriculture, aquaculture, livestock farming and otherallied activities for their livelihood. Human resources are the vital inputs in rural aquaculturedevelopment. Rural areas have vast potential of unutilized or underutilized human resources forboth men and women, which can be effectively utilized in operating aquaculture (Kumar et al.,1988).

Identification of possible constraints

A village survey also offers an excellent opportunity to identify various constraints in thebackground of which an appropriate strategy can be suitably designed.

Financial

Farmers usually do not have surplus funds big enough to be diverted towards reclamation and renovationof existing watersheds as well as construction of new ponds. Initial expenditure for fish culture over fishtoxicant, fish seed and supplementary feed is itself a considerably big amount to be exclusively borne byfarmers themselves without any credit support. As such, possible sources for mobilizing credit facilitiesmay be identified.

Improper water area distribution pattern

Like land distribution pattern, major water areas are usually found in the possession of medium and bigfarmers who bother least about fish culture and concentrate themselves mostly on agriculture, while smalland marginal farmers have minimum water holdings at their disposal with adequate manpower potentialto be utilized. In some areas most of the water bodies are vested to village institutions, localadministrative bodies, etc.

Lack of technical knowhow

Several seasonal and perennial ponds without any proper embankments are found lying fallow in aderelict condition due to ignorance and lack of technical knowhow. In some cases farmers fail to follow-up the prescribed package of practices strictly and land themselves in a state of financial turmoil and loseconfidence in the viability of newly developed fish farming technologies.

Lack of stocking materials and other material inputs

Fish farmers usually face the biggest problem of unavailability of quality fish seed for stocking their pond.Paucity of quality fish seed in the locality force the farmers to stock their ponds without any considerationto proper stocking size, density, species, ratio, etc. At times, they procure riverine fish seed which isusually mixed with the seeds of predatory and weed fishes. Other material such as fish toxicants areusually localised in its availability. All such problems are also vital for deciding area specific extensionstrategies.

Marketing problem

It is a general practice that the fish is sold to middlemen at the pond site who invariably pay lower prices.Due to the perishable nature of the commodity and fear of exploitation by the fish wholesellers, farmersprefer to sell the crop at their pond/farm sites even at relatively lower rates. Information related tomarketing practices will add to the scope of the extension programme so that farmers may be educated inmarketing management to avoid such exploitation.

Lack of transport and efficient communication system

In remote villages of India and many developing countries where fish culture technology needs to beextended, proper transport and communication facilities are lacking.

Social and administrative problems

Ponds remaining unutilized and lying in derelict conditions are common sights in rural areas in spite of acertain level of fish culture know how available with the farmers. In most cases such conditions exist dueto family rivalry and non-cooperation among the members of the owners especially when the water areasare under multi-ownership. Poaching and deliberate poisoning of the ponds to destroy the crop are alsoserious social problems. In some areas fish culture is supposed to be of a low-caste profession, thusmany efficient upper-caste prople remain reluctant to come forward for this venture. Local administrationsuch as Panchayats and Block Level Development Departments are also not always suitable gearedenough to ensure rural aquaculture development.

Setting programme goals and planning

In the light of resource inventory and possible limitations suitable target groups may be identified,programme goals may be set up and accordingly suitable extension strategy may be planned. Withoutsuch an early insight and planning, the programme may not have firm and realistic footing. Although thefish farmers are the usual target of any fish culture extension programme, all the fish farmers may not besuitable to be involved for immediate participation. Target groups may be selected on a number of criteriaincluding farming practice, production level, income, education, cultural background, nature, reputation inthe society, initiative, liable to change their attitude, etc. Selection of suitable communication channels isalso very important. Data collected during the pre-adoption survey provide the necessary information forsuch selection. After these selections, programme goals may be set up. Goals indicate the directiontowards which the programme is oriented. It also provides reference level for evaluating the programme

achievements (NACA lecture series No. 3). Examples of goals in such extension programme may be onthe following lines:

improving the socio-economic uplift of fish farmers and raising the standard of living;

bringing 100% of the available undrainable ponds for composite fish culture.

14.2.2 Programme implementation

“Plan the work and work the plan” is an appropriate term for any extension programme. Once the plan islaid, all possible efforts should be diverted to ensure that responsibilities are carried out, schedules arefollowed arid activities accomplished as per the plan (Kumar, Mohanty and Muduli) . Although thestrategies and planning of the aquaculture extension programme are situation specific, some generalsteps may be cited as follows;

Through heavy flow of information using mass media, publications, individual and mass contacts,etc., awareness and interest should be created among fish farmers.

One or two demonstration centres may be set up and the technology of composite fish culture andseed production in undrainable ponds may be demonstrated to maximum possible farmers to letthem realize the case of operation, production potential and profitability.

A set of suitable farmers should be selected initially and be motivated and guided enough so thatthey strictly follow the different package of practices as per the schedule.

Proper steps may also be taken to make available the critical material inputs at the pond/farm sitesand if the programme permits, subsidy should be given as a token of initial attraction.

If the availability of quality fish seed is found to be a limiting factor, fish seed may be distributed freeof cost or at concessional rate to the farmers at the initial stage. Proper attention may also be paidfor extending fish breeding and seed rearing programmes.

Facilities for proper monitoring of water quality and fish health may be extended through theparticipation of nearby laboratories.

Periodical netting for growth check/health inspection should be strictly followed and supervised.

Self-explanatory/pictorial instruction booklets dealing with basic steps of composite fish culture,control breeding of common carp, techniques of pituitary gland collection, induced breeding ofmajor carps, hatchery operation for carps, nursery and rearing pond managements, techniques offish seed transport, etc., may be prepared, explained and distributed among farmers.

Ad hoc training courses should be organized at the demonstration sites on different aspects of fishculture and fish seed production for participating and other interested farmers. Exhibitionprogramme/Fish Farmer's Day should be organized time to time at different places in which livespecimens of all the six carp species, other culturable air-breathing fishes, harmful predatoryspecies, weeds, fish feeds, fish toxicants, etc., should be shown and the objective and goal of theprogramme may be exhibited through models, charts, posters, etc. Sufficient time should also beprovided to discuss the farmer's problems under field conditions. Proper advice can be renderedimmediately and/or the problems should be forwarded to research institutions.

Daily talks on radio/tv may be organized to describe and discuss the technologies being extended.

At times a team of a few farmers may be selected on the basis of their leadership quality andperformance, and sent to visit important aquaculture centres, farms, research institutions, etc.

Individual contacts through home visits is a very effective extension method. The extension workermust be very clear in this objective during the visit and must do sufficient preparation with regard tosubject matter information he is going to deliver to the fish farmer and family members.

Evening is the most suitable time for organizing an assembly of farmers. Necessary details about

practices to be followed the next day may be explained to them during such assemblies. Teachingaids may be used to make the communication effective.

14.2.3. Programme evaluation

Programme evaluation is the process to determine the extent of success of the executed extensionprogramme in the light of present objectives. It is an important management function in order to ensureeffective implementation of the programme. It also helps in the identification of the deficiencies andweakness of the programme so that proper corrective measures may be taken to make it more useful inits future course. Programme evaluation can be conducted once a year or at a specific period of theprogramme and finally at the concluding phase of the programme. The process of evaluation alsodepends upon the nature of the programme. A short term and less extensive localized extensionprogramme may be evaluated by the extension workers themselves through the analysis of progressreports, field records, questionnaires, etc. However, broad-based and elaborate extension programmescan be evaluated by specialists in association with the extension workers to determine the effectivenessand impact of the extension programme.

It is convenient to fractionate the whole programme into smaller components for effective and easyevaluation. Fractionation may be done as follows:

Resources (financial, personnel an material) made available.

Objective of the programme in clear terms.

Phases of the programme (evaluation should also be done phase-wise).

Data collection from records and tabulation.

Selection of ways, means and methods for the collection of data/information from participating, non-participating fish farmers, village youths, prominent persons of the locality, etc.

Sample selection

Collection of data/information from target and non-target groups

Tabulation of data

Data analysis and interpretation of results

To measure the degree of success, certain values have to be associated with the information. Increasedfish production level, profit through increased fish yields, knowledge of modern management techniques,fish breeding, fish seed rearing, increased number of ponds/water areas in the area, etc. are some ofsuch measurable values for programme evaluation.

14.3 Important considerations

Extension services can be made most effective by making the people understand, accept andadopt the new technology, as it is very much clear from statistical data that people remember 10%of what they hear, 40–50% of what they see and hear and 90% of what they see, hear and do.

Maximum potential for development of undrainable pond fish culture lies in developing countrieswhere the prevailing literacy level is lowest.

The personality profile of extension workers is of prime importance for the extension of any rural-based aquaculture technology. He must mould himself enough so that he may become technical byprofession, social by temperament and preserve human values and missionary zeal of serving therural poor. He should be simple, easily approachable and adaptable enough so that he can liveamong fish farmers. At the same time he must not have any inferiority complex while meeting withspecialists and higher bureaucrats.

The target groups of aquaculture extension programmes are usually socio-economically backwardrural masses having a low level of literacy and technical knowhow, and are reluctant to bring aboutquick changes in their attitude.

Many extension departments and voluntary organizations are also of the opinion that the gains ofsocio-economic and technological development progrmames do net reach the rural poor and thatthe roots of this failure lies in the lack of organization of the poor themselves. Field workersexperience very often instances of diversion of financial grants meant for production programmesfor the small and marginal farmers into consumption subsidies. Similarly, there are numerousinstances where free educational facilities are granted for children of rural poor, but they hardlyavail the opportunity as they are treated as helping hands for supplementing family income. Most ofthe resources allocated for various welfare activities of the rural poor, however, are diverted intoactivities totally unrelated to mass welfare. The fact is that the poor are not only poor but aredisorganized and hence they have very little influence in the process of decision-making andimplementation of the programme. Under such conditions the concept of community fish farmingmay also be considered as an effective and ideal method for organizing at least a section of therural poor/fish farmers/fishermen in cooperative and productive communication (Tripathy,et al.,1982).

Support services and credit facilities are the two important factors which play major roles in theaquaculture development programme. Lack of appropriate support services and proper creditfacilities are the major drawbacks.

Effective institutional support to provide the necessary technical services needed by the extensionprogramme, such as site selection, pond designing, fish health check, pond environmentmonitoring, etc., are vital for programme implementation.



More details

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APPENDIX IMethods of Water Quality Analysis

1. Transparency

Fix a bright new pin at the “0” point of a meter scale and dip slowly into the pond water till the pin just disappearsfrom sight. The reading of scale at water surface gives the transparency value.

2. pH

pH values can be measured directly by a pH meter by dipping the electrode into the pond water or by colorimetricestimation as described below. Initially do the preparatory test with universal indicator to get the approximate valueof the pH. Place 10 ml of the water sample in the glass tube provided with the colour comparater and add 0.2 ml ofuniversal indicator. Shake gently and match the colour against standard colour disc for that indicator. Afterascertaining the approximate pH value use suitable indicators to determine the exact pH. Bromothymol blue for pHrange of 6.0–7.6, phenol red for 6.8–8.4 and thymol blue for 8.0–9.6 should be used as indicators. After addingthe required indictor stirr the sample and match the colour against appropriate standard colour disc and read thevalues.

3. Alkalinity

Reagents and equipments required:

i. 0.02(N)H2SO4 - Dilute 30.0 ml of conc.H2S04 (S. gravity 1.84) with distilled water to make 1 l to get approximately1(N) stock solutions. Take 20 ml of this solution and further dilute it to make 1 l to get 0.02(N) solution. Check itagainst 0.02(N) Na2CO3 using methyl orange indicator.

ii. Phenolphthalein indicator - 0.5% solution in 50% alcohol

iii. Standard 0.02(N) Na2CO3 - Dissolve 5.3 g anhydrous and dessicated Na2CO3 in 1 l distilled water to make 0.l(N)Na2CO3 stock solution. Dilute 50 ml of this solution to make 250 ml to give 0.02(N) Na2CO3.

iv. Methyl orange indicator - 0.05% aquous solution,

v. Glasswares

Procedure:

a. Phenolphthalein alkalinity (P)

Take 50 ml of the sample in white porcelain basin and add 2 drops of phenolphthalein indicator. If the sampleremains colourless (P) alkalinity is zero, but if it turns pink, titrate with 0.02 (N)H2SO4 through a burette to acolourless end point and calculate the value as per the following equation.

b. Methyl orange alkalinity (M):

Proceed as above using methyl orange as indicator, the end point is indicated by a colour change from yellow to

faint orange.

c. Dissolved Oxygen (DO) (Winkler's method):

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i. Alkaline iodide: Dissolve 700 g of pure potassium hydroxide (KOH) and 150 g of potassium iodide (KI) or 135 g ofsodium iodide (NaI) in 800 ml of distilled water. Cool it and make it to 1.0 1 by adding more distilled water.

ii. Manganous sulphate - Add 480 g of managanous sulphate (MnSO4.4H20 or 400 g of MnSO4.2H20) in 250 ml ofdistilled water, mix well and add more water to make the solution upto 1 l mark.

iii. Concentrated H2SO4 - (Sp. gravity 1.84)

iv. 0.025(N) Sodium thiosulphate - Dissolve 24.82 g of crystalline sodium thiosulphate (Na2S2O3.5H2O)in 700 ml ofdistilled water and add 4 g of borax (Na2B4O7.10H2O). Add more distilled water to make 1 l; after borax isdissolved.

v. 0.025(N) Potassium dichromate solution - Take 1.226 g of potassium dichromate (K2Cr2O7) and dissolve in 1 ldistilled water.

vi. Starch solution - Take 1 g of starch powder in 5 ml of cool distilled water, mix well and add 100 cc of boileddistilled water. Add 3 g of boric acid as preservative.

vii. Glasswares: Take 10.0 ml of 0.025 (N) K2Cr2O7 in a conical flask and add 1 ml of alkaline iodide, 2 ml ofConc.H2SO4 and titrate with 0.025(N) Na2S2O3 solution using starch as indicator.

Procedure:

Water samples for DO should be collected in 100 ml DO sample bottles without agitating, bubbling or mixing with airfrom the top column or bottom layer of the pond water as required. Immediately after collection, carefully remove thestopper and add 1 ml each of reagent (i) and (ii) by 1 ml pipette. Replace the stopper and thoroughly mix the contents.A whitish to deep brownish precipitate will be formed which will settle at the bottom. Whitish colour indicates poor DOlevel while more deeper the colour of the precipitate higher the DO level. Brown to red brown colour indicates medium tohigh DO concentration. Add 2.0 ml of conc. H2SO4 to dissolve the precipitate. Take 50 ml of this solution and titrate with0.025 (N) Na2S2O3 using starch as indicator to the colourless end point.

Calculation:

Dissolve oxygen (ppm) = ml of 0.025 (N) Na2S2O3 used X 4.

Dissolved free carbon dioxide:

Reagents and equipments required:

i. N÷44 Sodium carbonate (Na2CO3) - Dissolve 5.3 g Na2CO3 in 1 000 ml of distilled water. Dilute 100 cc of thissolution (N/10) to 440 ml with distilled water to get N/44 Na2CO3.

ii. Phenolphthalein indicator.

Procedure:

Take 50 ml of the sample in a conical flask and add 2 drops of phenolphthalein reagent. If the water turns pink there isno free carbon dioxide, if not, add N÷44 Na2CO3 drop by drop from a 10 ml graduated pipette with simultaneous gentlestirring with a glass rod till the colour turns pink.

Calculation:

Free carbon dioxide (ppm)

= ml of N÷44 Na2CO3 required × 20

Nitrogen (Ammonia and Nitrate nitrogen)

Reagents required:

i. Nessler's solution: dissolve 545.5 g of A.R. grade mercuric iodide and 35.0 g of potassium iodide (KI) in limitedvolume of ammonia free distilled water and finally add this mixture slowly to a cold solution of 112.0 g potassiumhydroxide (KOH) dissolved in 500 ml of ammonia free distilled water. Dilute to 1 l and allow to stand for few daysand finally the supernatant liquid is decanted off into dark coloured bottle and kept for use.

ii. Devarda's alloy

iii. Magnesium oxide (MgO)

iv. Ammonia free distilled water

v. Kjeldahl flask and other laboratory glasswares

Procedure:

Take 100 ml of filtered water sample in Kjeldahl flask and fit the flask with distillation unit. Add about 1 g MgO andstart distillation. Continue distillation till all the NH4-N distilled off. Collect 25 ml of the distillate. This contains NH4-N.

Add 1 g of Devarda's alloy to the remaining sample of the flask and start distillation again. Collect 25 ml of thedistillate in a separate receiver flask. This fraction of distillation contains NO3-N.

Place both the distillates in two separate Nessler tubes and add 0.5 ml Nesseler's reagent in each. Mix the solutionand match the developed colour against standard colour discs for ammonia and nitrate after 10–15 minutes with aNessleniser (BDH Nessleniser).

Calculation:

Amount of Ammonia/Nitrate Nitrogen (ppm)

= Number of matching division of the standard disc × 10 × 0.001 (Standard of each disc division).

vi. Dissolved Inorganic Phosphorus

Reagents required:

i. 2.5% sulphomolybdic acid - Dissolve 25 g pure ammonium molybdate in 1 200 ml distilled water by warming at60°C. Dilute 275 ml of concentrated sulphuric acid to 750 ml with distilled water separately. After cooling slowlymix ammonium molybdate solution to the diluted H2SO4 with constant stirring. Make the volume up to 1 l byadding more distilled water and store in dark bottles.

ii. 2.5% Stanous chloride - Dissolve 2.5 g of stannous chloride (SnCl2.2H2O) in about 5 ml of concentrated HCl withlittle warming. Dilute to 50 ml with freshly boiled distilled water and finally make the volume up to 100 ml by adding1.2(N) HC1. Preserve the reagent in dark bottle by overlaying a thin layer of pure liquid paraffin.

Procedure:

Take 50 ml of filtered water sample in a Nessler tube and add 2 ml of sulpho-molybdic acid and 5 drops ofstannous chloride solution. Mix thoroughly and compare the developed blue colour after 3–4 minutes in aNessleniser using standard colour discs for phosphate.

Calculation:

Phosphate (P2O5) in ppm

= Disc reading for 50 ml × 2 × .01

iii. Dissolved Organic Matter

Reagents required:

i. Standard KMnO4 solution (1 ml = 0.1 mg O2) - Dissolve 0.4 g potassium permanganate (KMnO4;) in distilled waterand make up to 1 l. One ml of this solution = 0.1 mg O2- This solution should be standardised against ammoniumoxalate solution in acid medium so that 1 ml of KMnO4= 1 ml of ammonium oxalate.

ii. Standard Ammonium Oxalate solution - Dissolve 0.888 g ammonium oxalate in distilled water and make up to 1 l.(1 ml of this solution = 0.1 mg of O2).

iii. Dilute sulphuric acid (1:3) - Add 100 ml of concentrated sulphuric acid slowly into 300 ml of distilled water.

Procedure:

Place 50 ml of the filtered sample water in a 250 ml conical flask and acidify by adding 5 ml of dilute H2SO4. Add10 ml of standard KMnO4 solution and keep on water bath for half an hour. After removing from water bath add 10ml of ammonium-oxalate solution. The pink colour of permanganate will disappear. With the help of a 10 mlgraduated pipette add drop by drop standard KMnO4solution till the colour just reappears. At times the pink colourdisappears while heating on water bath itself, in such cases 20 ml or more KMnO4 solution is to be added.

Calculation:

Oxygen consumed (ppm) = No of ml potassium permanganate required × 0.1 × 20.

APPENDIX II

Methods of Soil Quality Analysis

Minimum five samples should be collected from a larger pond from soft layer. However, the number of samples dependupon the variability of the soil quality. Mix all the samples well to get uniform composite sample. Samples should be airdried in shade and ground to fine powder by wooden hammer and strained through 2 mm sieve.

1. Soil Texture

1.1 Gravimetric method Required reagents:

i. Hydrogent peroxide (6.0%)

ii. (N) Hydrochloric acid

iii. (N) NaOH solution

iv. Silver nitrate solution (5%)

v. Concentrated Ammonium hydroxide solution

Procedure :

Take 20 g soil in a 400 ml beaker, add 35 ml H2O2 while keeping the beaker on water bath. Add more H2O2when the reaction is over till no more frothing takes place. Cool and add 50 ml (N) MCl and 200 ml distilledwater. Allow the content to stand for an hour with occasional stirring. Filter the soil and wash free of acid withhot water, tested by AgNO3 solution. Transfer the soil to 1 l beaker, add 8 ml (N)NaOH solution and shakefor 20 minutes in a mechanical shaker. The contents now should be transferred to a 1 000 ml measuringcylinder, shake vigorously for 1 minute and allow to stand for 4 minutes. Suck 20 ml of the content with a 20ml pipette from 10 cm level. Dry it in a beaker till constant weight is attained which gives the weight of siltand clay. Repeat the operation after 6 hours to get the weight of clay alone. The percentage of sand isobtained by deducting percentage of clay + silt from 100, similarly percentage of clay is substracted fromthat of clay + silt to get the percentage of silt.

1.2 Hydrometer method

Reagent required:

i. Sodium oxalate (COONa)2 0.5(N} solution - Dissolve 33.5 g sodium oxalate in 1 l of distilled water.

Procedure:

Place 100 g of air-dried finely powdered soil in a 500 ml conical flask and add 15 ml of 0.5(N) sodium oxalate. Add200 ml of distilled water and shake for 20 minutes. Transfer the content to 1 l capacity measuring cylinder andmake it up to 1 l mark by adding enough water. Stir the suspension thoroughly, stop stirring and note the time. Dipthe hydrometer in the suspension after 5 minutes which will give direct reading of the percentage of clay + silt.Hydrometer reading after 5 hours of sedimentation and the temperature of the suspension gives the percentage ofclay directly.

Calculation:

Hydrometer gives the reading in g/1 which can be converted easily into percentage of suspended matter.Percentage of sand is determined by deducting the percentage of clay + silt from 100. Similarly percentage of siltis determined by substracting the hydrometer reading for clay from the silt + clay. Normally the hydrometer readingis adjusted for the temperature of 19.4°C. Make correction to the scale reading by adding 0.3 units for everydegree of temperature above 19.4°C or substracting 0.3 units for each degree below 19.4°C.

ii. pH

2.1 Colorimetric method

Reagents required:

i. Neutral Barium Sulphate (A.R. grade)

ii. Indicator solutions - see Section 2 of Appendix I. Place a layer of neutral barium sulphate 1 cm thick in a 50 ml drytest tube, add 10 g of air-dried powdered soil sample and add 25 ml of distilled water, shake well and keep it forsettling. Take 10 ml of clear aliquot and follow the same procedure as under Section 2 of Appendix I.

2.2 Potentiometric method

Take 10 g of air-dried finely powdered soil sample in a beaker and mix well with 25 ml of distilled water and keepfor about half an hour with occasional stirring. Dip the electrodes/electrode of pH meter into it and take the readingdirectly.

iii. Organic Carbon

Reagents required:

i. (N) Potassium dichromate solution. Add 49.04 g A.R. grade potassium dichromate (K2Cr2O7) in distilled water-tomake it 1 l.

ii. (N) Ferrous solution. Dissolve either 278.0 g of A.R. grade ferrous sulphate (FeSO4.7H2O) or 392.13 g of ferrousammonium sulphate (FeSO4. (NH4)2 SO4.6H2O) in distilled water, add 15 ml of conc. H2SO4 and make thevolume to 1 l. Standardise against (N)K2Cr2O7 so that 1 ml of FeSO4 solution = 1 ml (N)K2Cr2O7 solution.

iii. Diphenyl amine indicator - Dissolve 0.5 g of diphenylamine in 10 ml conc.H2SO4 and 20 ml distilled water.

iv. Phosphoric acid (85%)

v. Conc. sulphuric acid (sp.gr. 1.84).

Procedure:

Place 1 g of soil sample (0.5 g and 2.0 g for soils with expected high and low organic C levels respectively) in a500 ml flask. Add 10 ml of reagent (i) and mix thoroughly. Add 20 ml of reagent (v) and mix gently by rotation.Allow the mixture to stand for 30 min. Add water to make up to 200 ml and then add 10 ml of reagent number (iv).Titrate with (N) Fe(NH4)2SO4 or (N)FeSO4 solution using 1 ml diphenylamine as indicator. At the end point colourof the solution sharply changes to a brilliant green. Carry out a separate standardisation blank also using all thereagents except the soil sample.

Calculation:

Organic carbon (%) = (Titration value (ml) for blank-titration value(ml) with soil) × 0.3

vi. Total Nitrogen

Reagents required:

i. Concentrated sulphuric acid (A.R. grade sp.gr. 1.84)

ii. Salicylic acid (A.R. grade)

iii. Sodium thiosulphate (Na2S2O3.5H2O)

iv. 12(N) Sodium hydroxide - Dissolve 480 g of sodium hydroxide (NaOH) pellets in distilled water and make up to 1 l.

v. 0.1(N) NaOH - Dissolve 4 g of NaOH pellets in distilled water, make up to 1 l and standardise against0.1(N)H2SO4.

vi. 0.1(N) Sulphuric acid (H2SO4) - Dilute 100 ml of (N) H2SO4 (stock solution - preparation under Section 3 ofAppendix I) to 1 l and standardise against 0.1(N) Na2CO3 solution.

vii. 0.1(N) Sodium carbonate (Na2CO3) solution. Dissolve 5.3 g of Na2CO3 in 1 l of water to get 0.1(N) standardsolution.

viii. Copper sulphate

ix. Potassium sulphate

Procedure:

Take 10 g of air-dried soil in a Kjeldahl's flask. Add 30 ml of conc. H2SO4, 1.0 g of salicylic acid, and keep in coldfor 1/2 hour. Now add 5.0 g of sodium thiosulphate and again keep for 1/2 hour. Add 1.0 g of powdered copper

sulphate and 10.0 g of potassium sulphate and digest the mixture. Clear blue colour of the solution indicatescompletion of digestion. Cool and transfer with water to an ammonia distillation flask. Make it alkaline with excessof 12(N)NaOH using phenolphthalein as indicator and distill off the ammonia collecting it in 25 ml of 0.1(N)H2SO4in a conical flask with a few drops of methyl red indicator. Collect about 150 ml of the distillate. Titrate the excessof 0.1(N)H2SO4 with 0.1(N)NaOH till the solution turns colourless.

Calculation:

Total nitrogen (%)

1. Available Nitrogen

Reagents required:

i. .02(N) sulphuric acid - see Section 3 of Appendix I

ii. 0.02 N sodium hydroxide - Dilute 100 ml of 0.1(N) sodium hydroxide (NaOH) of standard stock solution to500 ml with distilled water (Section 4 of this Appendix)

iii. Methyl red indicator - Dissolve 0.1 g of methyl red powder in 25 ml ethyl alcohol and make up to 50 ml withdistilled water.

iv. 0.32% potassium permanganate (KMnO4) - Dissolve 3.2 g of KMnO4 in distilled water and make the volumeup to 1 l.

v. 2.5% sodium hydroxide - Dissolve 25 g of NaOH pellet in 1 l of distilled water.

Procedure:

Take 10 g of air-dried and powdered soil sample in a Kjeldahl's flask. Add 100 ml of 0.32% KMnO4 and 100ml of 2.5% NaOH solutions. Distill the mixture after adding 2 ml of liquid paraffin and 10–15 ml of glassbeads. Collect 75 ml of the distillate in the receiving flask containing 25 ml of 0.02 (N)H2SO4 with a fewdrops of methyl red indicator and titrate with 0.02 (N) NaOH to a colourless and point.

Calculation:

Available nitrogen (mg/100 g soil) = (25 - No. of ml of 0.02 (N)NaOH required) × 2.8

2. Available Phosphorus

Reagents required:

i. 2.5% Sulphomolybdic acid (see Section 7 of Appendix I)

ii. 2.5% Stannous chloride (SnCl2) (see Section 7 of Appendix I)

iii. 0.002 (N) H2S04 - Dilute 50 ml of 0.02(N) H2SO4 (Section 3 of Appendix I) with distilled water to make up to500 ml mark and adjust the pH to 3.0 with (NH4)2 SO4 or K2SO4 (approximately 3 g/l)

iv. Standard phosphate solution

Dissolve 0.2195 g of dried monobasic potassium dihydrogen orthophosphate in 400 ml of water. Add 25 mlof H2SO4 (water mixture 1:5) and make the volume up to 1 l with addition of distilled water. This will give astock solution of 50 ppm of P (Phosphorus). Dilute 20 ml of this solution to 500 ml to get 2 ppm solution ofP. This 2 ppm of P solution, when diluted to 50 ml volume for the development of phospho-mollybdic bluecolour, gives the following values under different concentrations.

Procedure:

Standard curve: Take 0.5 ml, 1.0 ml 2.5 ml, 5.0 ml and 10.0 ml of 2 ppm solution of P in 50 ml capacityvolumetric flasks. Add 2.0 ml of sulphomolybdic acid in each. Make the volume up to 50 ml mark by addingdistilled water and add 5 drops of SnCl2 while shaking gently. The colour develops at its full intensity in 3–4minutes and begins to fade after 10– 12 minutes. Find out the respective optical density readings by thehelp of a photoelectric colorimeter or a spectrophomometer and plot the readings against the correspondingconcentrations of P to prepare a standard curve.

Take 1 g of air-dried and powdered soil sample in a glass bottle with stopper, add 200 ml of 0.002 (N)

H2SO4 solution and shake for 30 minutes with a mechanical shaker. Filter the suspension immediately on aWhatman No. 42 filter paper. Take 25 ml of the clear filtrate and find out the concentration of P in thatsolution through the standard curve.

Calculation:

Available P mg/100 g soil = ppm P in solution × 20.

APPENDIX III

Methods of Analysis of Feed and Feed Ingredients

1. Moisture

Requirements:

Petridish Drying oven Balance

Procedure:

Place pre-weighed 4–5 g of the sample in a covered petridish and dry at 100–105°C in a drying oven till constantweight is achieved.

Calculation:

Moisture content (%)

2. Crude Protein

Requirements:

i. Concentrated Sulphuric acid (A.R. grade - nitrogen free)

ii. Potassium sulphate (A.R. grade)

iii. Mercuric oxide (A.R. grade)

iv. Paraffin wax

v. Sodium hydroxide solution (40%) - Dissolve 40 g of NaOH pellets in 100 ml of distilled water.

vi. Sodium sulphide solution (4%) - Dissolve 4 g of sodium sulphide in 100 ml distilled water.

vii. Pumic chips

viii. Boric acid/indicator solution - Add 5 ml of indicator solution (0.1% methyl red and 0.2% bromocresol green inalcohol) to 1 l of saturated boric acid solution.

ix. Hydrochloric acid (0.1 N) - Dissolve 1.16 ml of concentrated A.R. grade HCl with distilled water to make 1 l.

x. Kjeldahl digestion and distillation units

xi. Kjeldahl flasks (500 ml cap)

xii. Conical flasks - 250 ml

Procedure:

Take exactly 1.0 g of sample into the Kjeldahl flask and add 10 g digestion mixture which consists of potassiumsulphate and copper sulphate in 9:1 ratio and 20 ml of sulphuric acid. Heat the flask gently at an tilted position tillfrothing stops and then boil until the solution becomes clear. To control excessive frothing add a small amount ofparaffin wax. Cool and add 90 ml of distilled water, leave it for some time and add again 25 ml of sulphuric acidand mix. To prevent bumping put small piece of boiling chips and add 80 ml of sodium hydroxide (NaOH) solutionwhile tilting the flask so that two layers are formed. Connect rapidly to the condenser unit, heat and collect distilledammonia in 50 ml boric acid/indicator solution. Collect the distillate. On completion of distillation, remove thereceived and wash condenser tip and titrate against 0.1(N) HCl.

Calculation:

Nitrogen content of sample (%)

Crude protein (%) = Nitrogen content × 6.25

If you suspect mixing of urea in the sample, then wash the sample thoroughly with distilled water and dry at 60°Cbefore proceeding for protein estimation.

xiii. Crude Fat

Requirements:

Petroleum ether (B.P. 40–60°C) Extraction thimbles/flasks Soxhlet extraction apparatus

Procedure:

Take 2.3 g of dried sample either in an extraction thimble or in a silk bag. Place the thimbles or the bag inside thesoxhlet apparatus/soxhlet flask. Connect a dry pre-weighed solvent flask beneath the apparatus and add therequired quantity of solvent and connect to the condenser. Adjust the heating rate to give a condensation rate of2–3 drops/ second and continue extraction for 16 hours. By increasing the extraction rate the extraction time maybe reduced. On completion remove the thimble. Remove ether completely on a boiling bath and then dry the flaskat 105°C for 30 minutes. Cool the same in a desicator and weigh.

Calculation:

Weight of the crude fat = Final weight of the solvent flask = Initial weight of the solvent flask.

If the extraction is done by putting the material in pre-weighed silk bags and hanging in extraction flask then followthe following calculation.

Weight of the crude fat = Initial weight of the bag with material - Final weight of the bag with the remainingmaterial.

xiv. Carbohydrate

Requirements :

i. Standard glucose solution - 100 mg in 100 ml of distilled water.

ii. Benedict's reagent

iii. 6(N)Hcl - Dilute 69.6 ml of concentrated HCl (A.R. grade) with distilled water to make 1 l volume

iv. Sodium carbonate

Procedure:

Take 100 mg of powdered sample and dissolve in 25 ml of water, add 25 ml of 6(N)HCl and heat in a water bathfor 3 hours at 100°C. Cool and neutralise with sodium carbonate until frothing stops and centrifuge the solution at2 000 rpm for 10 minutes or filter. Take the supernatant or filtrate and make upto 100 ml by taking enough distilledwater.

Take 5 ml of Benedict's solution in a conical flask, add 1 g of sodium carbonate and put some glass beads andtitrate against standard glucose solution. The titration must be done only in heated condition. Now the samevolume of Benedict's reagent is titrated against the hydrolysed sample solution.

Calculation:

Volume of standard glucose solution required for 5 ml of Benedict's reagent = A.

Volume of hydrolysed solution required for 5 ml of Benedict's reagent = B.

1. Ash

Concentrated Nitric acid

Silica crucible

Muffle furnace

Procedure:

Take 2 g of sample in a clean, dry silica crucible and place in a muffle furnace at 600°C for 6 hours. Cool and add2 drops of concentrated nitric acid. Again put the sample in muffle furnace and heat till white ash is produced. Coolthe crucble in the desicator and take the weight.

Calculation:

Weight of the crucible - Ag

Weight of the crucible + sample - B g

Weight of the sample - B-A = Cg

Weight of the crucible + ash - Dg

Weight of ash - D-A = Eg

APPENDIX IV

Methods of Community Structure Analysis

1. Plankton Analysis

Information on the abundance and variations of natural fish food organisms is necessary for proper fishery management.Methods of plankton analysis include collection of plankton samples and analysis of the samples both quantitatively andqualitatively.

1.1 Collection of samples

In fish ponds plankton samples are generally collected using a truncated cone shaped net by filtering known volume ofwater (normally 50 or 100 1). The plankton sieving net is the common equipment used and is made of bolting silk clothNo. 25 (# 0.064 mm mesh size) for phytoplankton and No. 13 (# 0.112 mm mesh size) for zooplankton.

The plankton cloth is cut based on the following calculations.

Using 1+X as radius, lay off the arc C on a piece of paper. At Centre h, lay off angle a by means of a protractor anddraw lines he and hf. With x as radius, draw arc C of smaller circle. Leaving 1 cm all along the sides, the cloth may becut and stitched and fitted onto a brass frame having wooden handle.

For he and hf, mark points at 90 + 53.3 = 143.3° and 90 - 53.3 = 36.7°

Usually about 50–100 1 of water is filtered through the plankton net and the sample is preserved in 5% formaldehyde. Inthe laboratory, the preserved plankton samples are analysed for quantitative and qualitative aspects.

1.2 Quantitative analysis of total plankton:

Settling volume:

Transfer the sample to a graduated cylinder or centrifuge tube and allow sufficient time (at least 6–8 hours) for planktonto settle at the bottom and record its volume and express the volume as ml of plankton/1 or ml of plankton/m3.Centrifuge of the samples may also be resorted to, for quicker analysis.

Wet weight:

The plankton sample is filtered through bolting silk cloth, excess water is blotted out and the residual material isweighed. The wet weight is expressed as mg/1 or g/m3 water.

Dry weight:

After taking the wet weight, dry the plankton samples in a hot-air oven at 60–80°C for about six hours and take theweight on a sensitive balance. Express the weight as mg/1 or g/m3.

Numerical count:

Dilute the filtered sample to a known volume, say 10 ml, and take for counting under microscope. Shake well the dilutedplankton sample and take one drop for counting on a glass slide and cover with a cover slip or take 1 ml of planktonsuspension in the Sedgewick- Rafter counting cell having a capacity of 1 ml with its area divided into 1 000 equalsquares. Count the number of plankters under microscope with 10x and 10x lenses. If 100 squares at random arecounted, and 100 1 water had been filtered, the number per litre will be given by X × 10 × 10÷100, where X is thenumber of plankters. While only the larger plankters are counted in the “survey count” method, all the plankters arecounted in the “total count” method.

1.3 Qualitative analysis of plankters:

The “differential count” method is usually followed which requires enumeration of some or all kinds of plankters,distinguishing them qualitatively into species or genera of phytoplankton and zooplankton. Shake well the dilutedplankton sample and take 1 ml of plankton suspension in Sedgewick-Rafter counting cell or one drop on a glass slideand cover with cover slip and count following the method described for numerical count. Instead of counting the totalnumber of plankton, count important groups of phytoplankton and zooplankton separately. Important groups ofphytoplankton usually encountered are green algae (chlorophyceae), diatoms (Bacillariophyceae), blue-green algae(Cydnophyceae), dinoflagellates (Dinophyceae) and chrysomonads (Chrysophyceae). Zooplankton in ponds mainlycomprise protozoans, rotifers, cladocerans, calanoid and cyclopoid copepods and their larval forms and occasionallynematodes and ostracods.

Based upon the total counts, percentage composition of the different forms as well as phytoplankton and zooplankton asa whole may be calculated with their seasonal variations.

2. Analysis of Benth Fauna

2.1 Sample collection:

Randomly fix sampling points covering various zones of the pond.

Collect sediment samples with the help of Ekman dredge for deeper ponds while glass tubes (both sides open; 7–10 cm dia and 30–40 cm long) for seasonal and shallow ponds. In case of sediment sample collection with tubes,the tube is gently placed on the sediment and then pushed further deep. The open end is then tightly closed with arubber stopper and the tube is lifted up with the contents. The contents are emptied onto an enamel tray.

Transfer each sample into a separate tray.

Dilute the sample with pond water, stir the sediment gently and pass it through seive. BSS 40 (mesh size 0.4 mmfor macrozoobenthos) or BSS 60 (mesh size 0.3 mm for meizoobenthos). Repeat the process till the samples arecompletely washed.

Transfer the sieved material to wide mouth bottles with little water in each and fix with 10% formaldehyde or 70%ethanol.

2.2 Quantitative analysis:

Numerical method:

Transfer the preserved samples into petridishes.

Segregate the organism into taxonomic groups with the help of pipette/forceps and magnifying glass orstereoscopic microscope.

Count them as total or under various taxonomic groupings and calculate the abundance of the organisms per unitarea as per the following equation.

n = Number of macroorganism per sampled area

a = Area of Ekman dredge or area of tube sampler

h = Number of hauls constituting a sample

Volumetric Method:

Blot dry the sample organisms with the help of filter paper and segregate them into taxonomic groupings.

Transfer them to tubes calibrated at 1 ml intervals and add water from a burette drop by drop till the organisme isfully submerged in the water. Substract the amount of water added from the burette, from the test tube readingwhich will give the volume of benthic organism.

Compute the volume of benthic macro-organism per m2 as a whole or individual groupwise with the help of thefollowing formula.

v = volume of macro-organisms/ sample

a = area of the Ekman's dredge/ area of the glass tube sampler

h = number of hauls constituting a sample.

Gravimetric Method:

Blot dry the samples group-wise on filter paper

Weigh them in a sensitive balance (wet weight)

Dry the above samples in an oven at 60–80°C to get dry weight (Exclude the shell weight of the molluscs)

The wet weight and dry weight of the benthos are expressed in g/m2.

APPENDIX V

Fish Health Examination RecordsCase No.: Date:

Locality:

Salient features of the water body:

Length 1 mm: Weight(g):

Condition: Fresh Refrigerated Frozen Fixed

Spoiled

External examination:

Look: Emaciated Healthy

Colouration: Normal Deeply pigmented

Other if any …

Check for cysts, spots, lesions, haemorrhages

parasite and abnormality if any

Body:

Fins:

Scales:

Operculum:

Eyes:

Mouth cavity:

Gills:

Microscopic examination:

Check for cysts, parasite, bacteria

Spores, lesions, inflamation

abnormality, etc.

Mucous/Scales

Fins

Gills

Liver

Kidney

Spleen

Intestine

Muscles

Eye

APPENDIX VI

Common Diseases, Their Symptoms and Treatment Measures DISEASE CAUSATIVE

AGENTCOMMON SYMPTOMS TREATMENT MEASURES

1 2 3 4A. Bacterial

diseases:

1. Columnarisdisease

Flexibactercolumnaris

Discoloured patches on the body,sloughing off of scales, erosion of gilllamellae, etc.

Copper sulphate 1 minute dip in 500 ppm solution0.25–2 ppm in pond treat ment depending uponhardness of water. Hard water requires more.

Potassium permanganate 1 minute dip in 500 ppmsolution; 3–5 ppm in pond treatment dependingupon organic content. Organic rich water requiresmore.

Penicillin + Streptomycin Injection for brood stock at30–40 mg of streptomycin and 20 000 i.u. ofpenicillin/ kg body weight prevents stress mediatedoutbreaks.

Terramycin (oxytetracycline) orally with feed at 7.5g/100 kg/ day for 10–12 days.

2. Bacteremia(Haemorrhagicsepticaemia)

Aeromonashydrophila,Pseudomonas

Shallow ulcerations, haemorrages and insevere cases the abdomen is swollen andthe scales protrude. Internally the body

Overcrowding, warmer conditions and oxygendepletion are some of the contributing conditions tobe avoided. Terramycin (oxytetracycline) with feed

fluorescens andpossibly others

cavity is filled with opaque fluid, paling ofliver and sometimes heamorrhages overswim bladder.

at 7.5 g/100 kg body weight/day for 10–12 days.Furaxolidone at 5–7.5 g/100 kg body weight/day for2–3 weeks. Pond treatment at 3–5 ppm ofpotassium permanganate is also a practicalapproach.

B. Fungal diseases 1. Saprolegniosis Saprolegnia spp. Ulceration or exfoliation of the skin, fin

erosion, exposure of muscles and jawbones and in some cases tufts of minutewhite hair like outgrowths may occur inthe affected regions.

Dip in treatment of 3% common salt solution or in500 ppm copper sulphate solution or in 500–1 000ppm of potassium permanganate solution till the firstsign of any distress. Swabbing with 10 000 ppm ofpotassium dichromate is also recommended.

2. Branchiomycosis Branchiomycesspp

Characterized by necrosis in the gill due tointravascular growth of this fungus.Histologically hyperplasia, fusing of gilllamellae and areas of acute necrosis areseen.

Improvement in water quality, avoidance of overfeeding, manuring, decreasing organic level in thepond, addition of freshwater together with treatmentmeasures suggested above are quite effective.Draining and liming the pond or treatment withbleaching powder is essential before initiating thenext culture operation.

C. Parasitic diseases:1. Protozoan diseases1.1 Ichthyophthiriasis

(white spotdisease)

Ichthyophthiriussp.

Presence of pin point size numerous whitespots on the body, fins, gills, etc. Theparasite can be observed in skin smear byits round ciliated body and horseshoeshaped nucleus. The disease is commonin nursery and rearring pond causing largescale mortality.

Mixture of malachite green and formalin at severalconcentrations are very effective. 0.05 ppm ofmalachite green and 25–50 ppm of formalin can beused as prolonged bath. Spraying the entire pondarea with malachite green at 0.15 ppm is veryeffective provided that 3 such applications are madeat 3 days intervals. Application of quick lime (CaO)at higher rate in the pond is also very effective.Several other antiprotozoan drugs are also in useagainst this disease.

1.2 Trichodinosis Trichodina sp. Discolouration of the body, presence ofthick mucous coat on the affected surface,frayed fins and gills are some of thecommon characteristics. Smear from gillsand skin readily exhibits parasites withradial ciliary band and central denticles.

Bathing in 1–2% solution of sodium chloride, 150–250 ppm of formalin, 0.25 ppm of malachite greenare very effective measures. Affected ponds shouldbe disinfected before next stocking.

1.3 Myxosporodiosis Myxosporidiansp.

Presence of white cysts of varyingdiameters on the body, fins, gills,opercula, etc. In some cases, emaciation,dark colouration together with presence ofcysts and spores in kidney tissues withoutshowing external cysts.

Infected fish should be immediately removed fromthe pond. Before inititing the next culture operationthe pond should be dried if possible and/orthoroughly disinfected with bleaching powder at 50ppm. Provision of settling tank before the waterintake in the pond also reduces the risk of infection.

2. Metazoan disease2.1 Monogenetic

trematodeinfection

Gyrodactylus sp.and Dactylogyrussp.

Heavily infected fish show increasedproduction of mucous, frayed fins, skinulcers and damaged gills. Microscopicobservation of the skin lesion/smear andtemporary mount of a portion of gill showthe presence of the parasites.

Bath in 100–250 ppm of formalin ranging from 1 to3 hours, is very effective. Dip in 2–5% salt solutiontill the first sign of distress is equally beneficial. Bathor pond treatment with some soft organophosphorusinsecticide is also equally effective.

2.2 Black spotdisease

Diplostomum sp. Development of small black or brownspots on several parts of the body andfins. Specific locations are cutis and underlying muscles. Microscopic examinationand dissection helps in locating rolled upand slowly moving worms embedded inthe connective tissue.

Fish exhibiting black spots may be given an hourbath in 10 ppm picric acid solution. Removal ofaquatic snails and preventing the entry of birds aresome of the preventive measures. Infection does notspread from fish to fish and hence it is not worthtreating uninfected stock.

2.3 Argulosis Argulus sp. Development of haemorrhagic patchesover the body and presence of theparasite in large number in and aroundthe lesion.

Benzene hexachloride application in pond at 0.02ppm a second subsequent treatment after a week.Affected fish should also be given dip in 500–1 000ppm potassium permanganate solution which helpsin avoiding secondary infection as well as acceleratethe healing process. Malathion at 0.25 ppm in pondalso effectively controls the infection. Malathion alsorequired a second treatment after a week interval.

2.4 Leraeasis Lernaea sp. Anaemia, severe ulcerations and presenceof attached cylindrical parasite of 1 to 2cm length hanging outside. Sometimescause mass mortality in carp nursery andrearing ponds.

Baths in concentrated solution of salt and potassiumpermanganate is reported to be effective. However,the author has found very little improvement bypotassium permanganate treatment. Juveniles areembeded in the skin and hence remain unaffected.Chlorophos a Diptrex or Neguvan when applied inthe pond at 0.25 ppm kills all the parasite. Bromex

completely cures the infection when applied at 0.15ppm.

2.5 Leech infection Piscicola sp. Relatively they are not dangerous. Theyaffect the fish by their attachment andfeeding. Area of attachment normallyexhibit excessive mucous production,hyperaemia and petechial haemorrages.Inflamation and epithelial hyperplasiaextending through the dermis may beobserved. Open wounds are often infectedby bacteria and fungi. Attacked fish showattached parasite, irritation andrestlesness. They may attempt to rubagainst objects.

Removal of aquatic vegetation and maintenance ofpond hygene is the most important preventivemeasure. Hard objects such stones, logs, etc.should also be removed. Disinfection of pond withunslaked lime at 2 500–3 000 kg/ha should be doneprior to next rearing operation. Short bath in 3–5%salt solution is also very effective treatment. Dip in 1000 ppm acetic acid or 10 000 ppm in potassiumpermanganate solution are also quite effectivemeasures. Organophosphorus insecticides asdescribed in earlier cases can also be used.

APPENDIX VII

Book Keeping

Book keeping is the core of fish farm management which records all aspects of fish farm operations and enable the fishfarmer/farm manager or the extension officer to understand the economics of the pond/farm operation, provideinformation for planning developmental projects and better services for fish farmers, and also to provide necessaryground to get funding support from financial institutions.

The book-keeping system has the following two major aspects of recording:

A. Account keeping

B. Operational activities

A simplified form of this system is described which can be used by fish farmers/fish farm managers and extensionworkers.

A. Account Keeping

Maintain 2 thick bound registers one as Cash Book (CB) and the other as Ledger Book (LB). Number the pages in CashBook keeping the same page number for both right and left facing pages. Keep left pages for receipts and right pagesfor payments. Calculate closing balance (CB) for the day which will become opening balance (OB) for the following day.Number all pages of the Ledger Book (LB) and keep at least one page for each item as shown by giving examples of 8pages. Number of pages for each item depends on the extent of recurring expenditures or receipts under that head.Accordingly, enough page space should be kept under that head so that it may cover a period of 1 year. Enter thedetails of receipts and payments on daily basis in both of these registers. To analyse the performance of individualsector or a particular pond of the farm, pond-wise or sectorwise separate entries should be made in the ledger book andin such cases separate pages should also be provided for each pond. For example, for fish sale, there should beseparate pages for each pond. Accordingly, entries should be made under fish sale of pond No. 1 or Fish sale of pondNo. 2, etc. This will give a complete record of everything you spend and any money you receive.

1. Cash Book (CB)

Receipts always on left page of the Cash Book

Receipts Page 1/L

Date Particulars of receiptsLedgerBook

Page No.Amount(US$)

7.1.1987 Capital Acct. Received loan money from the State Bank of India, Bhubaneswar 1 2 500.00 2 500.008.1.1987 Opening balance (OB) 1 000.00 Sale proceeds (fish)

Received towards sale of 100 kg of unwanted fish at US$ 1.50/kg after bleaching powderapplication 2 150.00

Sale proceeds fingerlings Received towards sale of 50 000 fingerlings of catla at US$ 200/1 000 3 10 000.00 11 150.009.1.1987 Opening balance 2 106.00

Payments always on right page of the Cash Book

Payments Page 1/R

Date Particulars of expenditure Ledger Bookpage No. Amount (US$)

7.1.1987 Pond Construction Construction of one nursery pond 4 1 000.00 Maintenance of Pond Repair of dyke of stocking pond No.7 5 500.00 Total: 1 500.00 Closing balance 1 000.00 2 500.008.1.1987 Labour Charge 2 labourers for pond poisoning at US$ 20.00 per labourer/day 6 40.00 Piscicide 100 kg of bleaching powder at US$ 4.00/kg 7 400.00 Total: 440.00 Closing balance 2 106.00 2 506.00

2. Ledger Book (LB)

Capital Page 1

Date ParticularsCB

pageNo.

DebitAmount(US$)

CreditAmount(US$)

7.1.87 Loan money from State Bank of India, Bhubaneswar Branch 1 2 500.00

Fish Sale Page 2

Date ParticularsCB

pageNo.

DebitAmount(US$)

CreditAmount(US$)

8.1.87 100 kg of unwanted fish sold at US$ 1.50/kg 1 150.00

Ledger Book (LB)

Fry Sale Page 3

Date Particulars CB pageNo.

Debit Amount(US$)

Credit Amount(US$)

8.1.87 Sale of 50 000 catla fingerlings at 200/1 000US$ 1 10 000.00

Pond construction Page 4


Debit Amount(US$)

Credit Amount(US$)

7.1.87 Construction of one nursery pond 1 1 000.00

Ledger Book (LB)

Maintenance of pond Page 5


Debit Amount(US$)

Credit Amount(US$)

7.1.87 Repair of pond dyke of stocking pond No. 7 1 500.00

Maintenance of pond Page 6


Debit Amount(US$)

Credit Amount(US$)

8.1.87 2 labourers for application of bleaching powder for pond poisoningat US$ 20.00 per labourer 1 40.00

Ledger Book (LB)

Piscicide Page 7Date Particulars CB page No. Debit Amount (US$) Credit Amount (US$)

8.1.87 100 kg of bleaching powder e US$ 4.00/kg 1 400.00

Fish Feed Page 8Date Particulars CB page No. Debit Amount (US$) Credit Amount (US$)Item Present Expected Annual Monthly

3. Annual Balance Sheet

An Annual Balance Sheet form should be prepared after a year of farm/pond operation which will show how much isearned and what the fish farm is worth. It makes a summary of everything that has been recorded in cash book (CB)and ledger book (LB). Make total of every item in the LB and put it in the Annual Balance Sheet. If required MonthlyBalance Sheet can also be prepared taking monthly total of every item, from the LB.

4. Depreciation Cost

Depreciation cost is the amount of value an expensive item loses every year and this amount one must keep aside toreplace the item when it is worn out. To work out depreciation cost for any item, for example a pump set, one shouldconsider the following two aspects:

i. What would be its expected life? Say 10 years

ii. What is the present value?

For each such item put these two figures in respective column in the following form and calculate annual or monthlydepreciation cost.

Item (Asset) Present cost Expected life Annual depreciation Monthly depreciationPump set $ 1 000 10 years $ 100 $ 8.33Net $ 500 6 years $ 83.3 $ 6.94

1.3 Annual Balance Sheet

YEAR …

Month Cost of Production Sales Income NetIncome*

Pond/farmconstruction

Maintainanceof pond/farm

Labourcharges Piscicide Fish

seedFishfeed

Sparesetc.

TotalFish

Fishseed Total

January February March April May June July August September October November December

* Net Income = Sales Income - Cost of Production

5. Loan Accounting

A separate loan record sheet should also be maintained if the farmer has taken any loan for fish farming. For example, ifthe farmer has taken a loan of $ 500 from the Government for pond construction and that has to be repaid in 10 yearswith an annual interest rate of 10%, with the assistance of the Extension Officer, the fish farmer should keep a record ofhis loan repayment. The interest paid on the loan should be regarded as a production cost and should be taken intoconsideration in calculating the net income of the fish farming operation. A simple loan record sheet is given below:

Loan 1 Loan 2State Bank of India Bank of India,

Source: Muzaffarpur Source: MuzaffarpurDate … Date…Amount… Amount…Period of repayment… Period of repayment…Annual rate of interest… Annual rate of interest…

Repayment Detail Repayment Detail

Date InterestPayment

LoanRepayment

LoanOutstanding Date Interest

PaymentLoan

RepaymentLoan

Outstanding

Total:

B. Operational Activities

Aspects pertaining to the description of the ponds/farm, plan of work, operational activities such as prestocking, stockingand poststocking operations, monthly sampling details, harvesting, induced breeding, fish seed rearing, etc. should alsobe recorded. Formats, with examples, for recording such activities are presented hereunder.

1. Pond Description

POND NO. DESCRIPTION 1 2 3Age(years 5 4 1/2Nature of earlier operations if any Composite fish culture Culture of 3 Indian major carps Rearing of fish seedAverage annual Production rate 5 500 kg/ha 3 400 kg/ha

Pond area (m2) 2 000 3 000 200

Water depth (m) 2.5 1.5 0.7Sediment depth (cm) 15 10 8Water source Irrigation canal Rain Rain

2. Farming plan:

POND NO. FARMING PLAN 1 2Type of farming Composite fish culture Fish seed rearingSpecies Catla, rohu, mrigal, silver carp, grass carp, common carp Silver carp, grass carp,Stocking density 6 000/ha 6 million/haManuring Cowdung Poultry manureFeeding Fish feed Micro-encapsulated feedPeriod of rearing 12 months 3 weeks

3. Pre-stocking operations:

POND NO.OPERATIONS 1 2

1. Pond clearing Weed clearing using manual method Weed clearing using weedicides

2. Eradication of unwanted fish Poisoning-250 kg of bleaching powder applied in the pondat 50 ppm

Poisoning-1 125 kg of mahua oil cake at250 ppm

3. Liming 60 kg of lime at 200 kg/ha4. Organic manuring

4. Stocking details:

POND NO. STOCKINGDETAILS 1 2

1. Date of stocking 15.11.86 10.10.86

2. Species stocked Catla (C), rohu (R), Mrigal (M), Silver carp (S) , Grass carp (G),Common carp (CC) R, C, R, M

3. Stocking density 6 000/ha 5 000/ha4. Number stocked 1 200 1 5005. Species ratio C 2; R 3; M 1.5; S 1.5; G 0.5; CC 1.5 C 4; R 3; M 3

6. Seed treatment Short bath in potassium permanganate solution Short bath in 2% saltsolution

7. Average weight (g) C-50; R-60; M-50; S-40; G-50; CC-30 C-50; R-60; M-50

5. Post-stocking operations:

POND NO.

MONTH OPERATIONS November December OctoberOrganic manuringLimingInorganic fertilizerFeedingMedication

6. Monthly sampling details (growth):

DATE SPECIES 1.12.86 A/B 2.1.87 A/BCatla 50/10 70/20Rohu 40/8 60/20Mrigal 30/8 48/18Silver carp 35/15 55/20Grass carp 42/16 60/18Common carp 48/18 65/17

7. Standing crop of fish (estimation)

POND NO. 1 MONTH: DECEMBER 1986

Species Av. Wt. attained (g) No. stocked Mortality Total weight (kg)Catla 150 240 10 34.5Rohu 140 360 - 50.4Mrigal 130 180 - 23.4Silver carp 185 180 - 33.3Grass carp 190 60 - 11.4Common carp 90 180 10 15.3 Total 1 200 20 168.3

8. Harvesting details (Table size fish production):

POND NO. POND SIZE: DATE:

SPECIES DETAILS Catla Rohu Mrigal Silver carp Grass carp Common carp TotalNo. stockedNo. harvestedSurvival (%)Averageweight (g)Totalweight (kg)SpeciesContribution %

Gross Production (Kg) = Total weight of harvest (Kg)

Net Production (Kg) = Gross production (Kg) - Initial stocking weight (Kg)

9. Harvesting details (Fish seed rearing):

POND NO. Period of rearing (days) Species No. harvested Survival % Av. Wt. (g) Remarks

10. Induced breeding:

DATE Species Weight(g)

InducingagentDose

(mg/kg)

Setsattempted

(No.)Spawning

success (%)Estimated No.

of spawn Remarks

Male Female

APPENDIX VIII

Essential Items for a Farm (Self Sufficient 5 ha Unit)

A. Table size fish farming sector:

1. Nylon seive net pieces with head rope, foot rope, sinkers and floats. 40 mm meshed (10 m × 6 m) - 10 pieces 20 mm meshed (10 m × 6 m) - 10 pieces (Mesh size should be measured knot to knot diagonally)2. Hand net (Scoop net) of 25 mm mesh Nylon material with aluminium/cane framing open at both ends - 5 closed at distal end - 53. Spring balances of the following capacities: 1 kg — 2 Dial type 5 kg — 2 Dial type 20 kg — 24. Plastic buckets with lids of the following capacities: 2 l – 6 5 l – 6 12 l – 6 25 l – 25. Plastic or enamel trays - 66. Plastic tub/galvanized iron sheet tub/ fibreglass circular tank- 57. Spade - 58. Bottom raker - 29. Sickle - 610. Pick-axe - 211. Grass cutting knives - 612. Crowbar - 413. Hammer - 214. Rope of various sizes - 1 roll each15. Torches (3 celled) - 416. 5 HP diesel pump set with generator set attachment option - 117. Generator set to be driven by 5 HP diesel engine - 118. Small boat - 119. Mini tractor with trailer - 120. Bamboo hanger for drying

the net - 121. Cane baskets - 1022. Anti-poaching devices: - Unfinished bamboo - 100 - Bamboo poles - 200 - Barbed wire - 5 rolls23. Nylon twine (assorted size) - 1 kg24. Conditioning hapa (cotton) - 1025. Towels - 426. Bamboo baskets (50 kg capacity) - 1027. 200 kg capacity balance with tripod stand and set of weights - 128. Spare gunny bags - 2029. Umbrella - 430. Rain coat - 631. Gum boot - 6 pairs32. Fish measuring board - 233. Feeding tray (galvanized iron sheet) (50 cm × 100 cm × 15 cm) - 2034. Mini tractor operated compressor - 1

B. Fish Seed Production Sector:

In addition to the items listed under A, the following items are also needed.

1. Nylon seive net pieces complete with head rope, foot rope, sinkers and floats 1.5 mm meshed (10 m × 5 m ) - 2 3 mm – 4 mm meshed (10 m × 5 m) - 52. Hand net (scoop net) with opening at both ends and having a thick twine at the distal end for tying. 25 mm meshed nylon netting - 12 3 mm – 4 mm meshed nylon/cotton netting - 53. Canvas strechers with provision of net cover for brood fish transport in the farm - 24. Nylon breeding hapa - 105. Nylon hatching hapa: Outer - 100 Inner - 506. Bamboo poles - 1507. Jute or cotton twine - 2 kg8. Cheesecloth for holding brood fish - 5 m9. Plastic buckets graduated 1 l - 10 5 l - 10 12 l - 1010. Plastic/enamel mug graduated - 611. Enamel tray - 1012. Enamel basins 3–5 1 capacity - 1013. Feathers - 5014. Folding work table - 115. Folding chairs - 416. Set of dissection instruments - 217. Centrifuge machine (hand operated) - 118. Centrifuge tubes graduated - 2019. Petridishes (assortment) - 2020. Dropper with long nozzle - 2021. Tissue homogenizer - 522. Beaker - 50 ml capacity - 10 100 ml capacity - 10 250 ml capacity - 1023. Clean homoeopathic tube with stopper - 20024. Hypodermic syringes - 2 cc capacity - 5 5 cc capacity - 525. Hypodermic needles No. 20 - 12

No. 21 - 12 No. 22 - 1226. Pituitary gland - 1 000 nos. (10 000 mg)27. Absolute alcohol - 450 ml × 228. Distilled water (sterile) - 200 ampoules29. Spawn measuring cup 10, 25, 50 ml capacity - 1 each30. Strainer cup for measuring fry 100 ml, 500 ml - 2 each31. Oxygen cylinder with regulator pressure gauge and dry oxygen gas - 232. Plastic bags/cylindrical rolls thickness 0.3 - 0.5 mm circumference 100–150 mm - 10 rolls/5 000 nos.33. Thermometer (0–50°C) - 234. Brushes for cleaning metal, plastic, glass appliances (assorted sizes) - 2035. Stereoscopic microscope with stage lightning - 136. High power hand lense - 137. Cotton twine for tying the oxygen packed bags - 5 kg38. Butcher's knife - 239. Acetone - 450 ml × 240. Desicator with silica gel - 241. Porcelain pestle and mortar (5–10 cm dia) - 242. Widemouth bottle with glass stoppers - 1043. Cotton wool - 2 kg44. Rubber cushion (60 cm × 40 cm × 5 mm) - 245. Cathetors (2.5 mm dia) - 2

C. Piscicides, feeds, manures and fertilizers

Bleaching powder/mahua oil cake

Rice polish

Groundnut/mustard oil/soyabean cake

Mineral mixture

Fish meal

Raw cow dung/poultry manure/pig dung

Urea

Ammonium sulphate

Super phosphate

Muriate of potash

Lime

To avoid storage loss of nutrients and spoilage, it is desirable to buy the items on regular basis. The selection of itemsalso depends upon the local availability and relative market prices. However, the store should have sufficient amount ofready stock of these items so that they may last for 3–4 weeks.

C. Medicine Chest

Sodium choride (common salt) - 5 kgCopper sulphate - 5 kgPotassium permanganate - 500 g × 10Organophosphate insecticide (Malathion/Somithion) - 1 l × 5Benzenehexachloride (BHC) wettable powder - 500 g × 10 packsFormaldehyde (formalin) - 10 l × 1Acetic acid (glacial) - 500 ml × 10Quick lime - 50 kg × 5 packsBleaching powder (sodium hupochlorite) - 25 kg × 10 bagsOxytetracycline - 100 g × 10Penicillin - 10 vialsStreptomycin - 10 vials

Malachite green (zinc free salt) - 10 g × 5



More details

FAO FISHERIES TECHNICAL PAPER 325

Fish culture in undrainable pondsA manual for extension

TABLE OF CONTENTS

byDilip Kumar

Central Institute of Fisheries EducationIndian Council of Agricultural Research

Versova, Bombay, India

The designations employed and the presentation ofmaterial in this publication do not imply the expression ofany opinion whatsoever on the part of the Food andAgriculture Organization of the United Nationsconcerning the legal status of any country, territory, cityor area or of its authorities, or concerning the delimitationof its frontiers or boundaries.

M-44ISBN 92-5-103139-8

All rights reserved. No part of this publication may be reproduced, storedin a retrieval system, or transmitted in any form or by any means,electronic, mechanical, photocopying or otherwise, without the priorpermission of the copyright owner. Applications for such permission, witha statement of the purpose and extent of the reproduction, should beaddressed to the Director, Publications Division, Food and AgricultureOrganization of the United Nations, Viale delle Terme di Caracalla,00100 Rome, Italy.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome,© FAO

PREPARATION OF THIS DOCUMENTThis document has been prepared within the framework of the Regular Programme activities of the InlandWater Resources and Aquaculture Service of the Fishery Resources and Environment Division. Theprimary objective of this document is to assist extension workers and other field personnel engaged infish culture in undrainable ponds to increase production through the application of improved culture

http://www.fao.org/




technology.

The original manuscript was prepared by Mr. Dilip Kumar of the Central Institute of Fisheries Education,Bombay, India, based on the Indian experience of fish culture in undrainable ponds, and it was edited byMr. P.C. Choudhury. It is hoped that this manual will be useful to extension workers and fish farmers inareas where fish ponds are not drainable.

Kumar, D.

Fish culture in undrainable ponds. A manual for extension.

FAO Fisheries Technical Paper No. 325. Rome, FAO, 1992. 239 p.

ABSTRACT

This manual deals with the methods of freshwater fish culture in undrainableponds as practised in India. The manual is primarily meant for extension workersand aquaculture training institutions. It outlines the basic principles of fish cultureand the characteristics of undrainable ponds. The systems of composite carpculture and composite carp culture-livestock farming have been described.Methods of improvement of existing ponds and construction of new ponds havebeen included. The suitable species for culture, procurement of their seed,stocking ratios of various species under composite culture, etc., have beendiscussed. Pond management, both pre-stocking and post-stocking, including fishhealth management and management of common hazards have been dealt with. Italso contains information on marketing and economics of fish culture inundrainable ponds.

Distribution:

FAO Fisheries DepartmentInland Waters - GeneralFAO Regional Fisheries OfficersAuthor

ACKNOWLEDGEMENTSSincere gratitude is expressed to the Fisheries Department of the Food and Agriculture Organization ofthe United Nations for suggesting and sponsoring the preparation of this manual and to the IndianCouncil of Agricultural Research (ICAR), Ministry of Agriculture, Government of India, for kindly permittingme to take up this job. The author is indebted to Drs. R.M. Acharya, P.V. Dehadrai, and M.Y. Kamal,ICAR Headquarters, New Delhi, who were instrumental in obtaining this permission. Sincere support,encouragement, valuable guidance and never-ending help is extended to Drs. V.R.P.Sinha, S.D. Tripathi,and A.G. Jhingran. The author extends his heartfelt thanks to Dr.N.G.S. Rao, Mr. M. Ranadhir, Mr. H.A.Khan, Mr. B.B. Satpathy and Dr. B.N. Singh for critically going through the relevant chapters of themanuscript. Finally, he is glad to acknowledge the tremendous help provided by his colleagues Mr.Kuldeep Kumar, Dr.S.K.Sarkar, Mr. C.D. Sahoo, Dr. S.N. Mohanty, Dr. N. Sarangi, Mr. M.S.Tantia, Mr.R.K.Dey, Mr. A.K. Sahoo, Mr.S. Ayyappan, Mr. C.S. Purushothaman, Dr. K. Jankiram, Mr. D.Narayanswamy, Mr. B.K. Mishra, Mr. Radheyshyam, Sri P. Jena, Sri R.C. Behera and at the end he alsowishes to express his sincere thanks to his parents, wife and family members who gave their totalsupport.

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for theopinions, ideas, data or products presented at these locations, or guarantee the validity of the informationprovided. The sole purpose of links to non-FAO sites is to indicate further information available on related

topics.

TABLE OF CONTENTS

1. INTRODUCTION1.1 Fish as food

1.2 High multiplication capacity and minimal water requirement1.3 Low energy requirement for protein production1.4 Warm water favours fish growth1.5 Aquaculture production potential1.6 Employment potential2. PRINCIPLES OF FRESHWATER FISH CULTURE2.1 Pond ecosystem2.2 Oxygen budget2.3 Desirable fish species for culture2.4 Living space2.5 Supplementary feeding2.6 Pond fertility2.7 Diseases and their control3. CHARACTERISTICS OF UNDRAINABLE AND DRAINABLE PONDS3.1 Undrainable ponds 3.1.1 General morphometry 3.1.2 Physico-chemical environment 3.1.3 Community structure and function3.2 Drainable ponds4. PRESENT PRACTICES OF FISH CULTURE IN PONDS4.1 Carp culture4.2 Integrated carp farming 4.2.1 Integrated fish-pig farming 4.2.2 Integrated fish-duck farming 4.2.3 Integrated fish-poultry farming4.3 Air-breathing fish culture4.4 Sewage-fed fish culture5. RENOVATION OF EXISTING PONDS5.1 When to take up the renovation work5.2 Deweeding5.3 Dewatering and drying5.4 Contouring5.5 Desilting5.6 Reclamation of derelict water bodies5.7 Maintenance of dykes6. CONSTRUCTION OF NEW PONDS AND FARMS6.1 Site selection 6.1.1 Topography 6.1.2 Source of water and its quality 6.1.3 Soil type6.2 Designing 6.2.1 Water area ratio among pond types 6.2.2 Dyke6.3 Construction 6.3.1 Time of construction 6.3.2 Preparation of site 6.3.3 Marking the outlines

6.3.4 Pre-excavation work 6.3.5 Pond excavation and construction of dykes 6.3.6 Water inlet structure6.4 Maintenance7. FISH SPECIES SUITABLE FOR CULTURE IN PONDS7.1 Criteria for selection of suitable fish species7.2 Fish species suitable for culture in undrainable ponds 7.2.1 Catla 7.2.2 Rohu 7.2.3 Mrigal 7.2.4 Silver carp 7.2.5 Grass carp 7.2.6 Common carp8. PROCUREMENT OF INPUTS8.1 Procurement of seed 8.1.1 Collection of spawn from riverine sources 8.1.2 Bundh breeding 8.1.3 Induced spawning by hypophysation 8.1.4 Production of common carp seed8.2 Feed 8.2.1 Natural food 8.2.2 Supplementary feed8.3 Fertilizers 8.3.1 Organic manures 8.3.2 Inorganic fertilizers9. POND MANAGEMENT9.1 Pre-stocking management 9.1.1 Eradication and control of aquatic weeds and algae 9.1.2 Eradication of unwanted fish 9.1.3 Eradication of predatory insects 9.1.4 Fertilization of ponds9.2 Stocking 9.2.1 Stocking of nursery ponds 9.2.2 Stocking of rearing ponds 9.2.3 Stocking of growout/stocking ponds 9.2.4 Method of stocking9.3 Post-stocking management 9.3.1 Feeding 9.3.2 Periodic fertilization 9.3.3 Pond environmental monitoring 9.3.4 Fish health monitoring10. MANAGEMENT OF COMMON HAZARDS10.1 Deficiency of dissolved oxygen10.2 Appearance of algal blooms10.3 Common carp problem10.4 Problem of no rain and plenty of rain10.5 Problem of predation

10.6 Poaching10.7 Leakages in embankment10.8 Outbreak of diseases 10.8.1 General considerations 10.8.2 Common diseases 10.8.3 Therapy of fish diseases11. HARVESTING11.1 Harvesting in nursery ponds11.2 Harvesting in rearing ponds11.3 Harvesting in growout ponds 11.3.1 Complete harvesting 11.3.2 Partial harvesting11.4 Application of proper gear11.5 Precautions12. TRANSPORT AND MARKETING12.1 Transport of fresh fish12.2 Transport of live fish 12.2.1 Conditioning and preparation for transport 12.2.2 Open system of transport 12.2.3 Closed system of transport 12.2.4 Drugs and chemical aids12.3 Marketing 12.3.1 Market potential 12.3.2 Marketing of table-size fish 12.3.3 Marketing of fish seed13. ECONOMICS OF CULTURE OPERATIONS13.1 Raising of fry13.2 Raising of fingerlings13.3 Raising of table-size fish14. AQUACULTURE EXTENSION14.1 Objective14.2 Launching aquaculture extension programme 14.2.1 Programme planning 14.2.2 Programme implementation 14.2.3 Programme evaluation14.3 Important considerations15. REFERENCESAPPENDICES

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FAO Fish Culture in Undrainable Ponds