Nutrition and Feeding for Sustainable Aquaculture Development in the Third Millennium

8/11/2019 Nutrition and Feeding for Sustainable Aquaculture Development in the Third Millennium

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Nutrition and Feeding for SustainableAquaculture Development in the

Third Millennium

M.R. Hasan1

Department of Aquaculture, Bangladesh Agricultural University,

Mymensingh 2202, Bangladesh

san, M.R. 2001. Nutrition and feeding for sustainable aquaculture development in the thirdllennium. In R.P. Subasinghe, P. Bueno, M.J. Phillips, C. Hough, S.E. McGladdery & J.R. Arthur, eds.uaculture in the Third Millennium. Technical Proceedings of the Conference on Aquaculture in theird Millennium, Bangkok, Thailand, 20-25 February 2000. pp. 193-219. NACA, Bangkok and FAO,me.

BSTRACT: Over the last decade, the world has witnessed spectacular growth in the aquaculturedustries of many developing countries. It is unequivocally agreed that global aquaculture productionll continue to increase, and much of this will occur in the developing countries of Asia and Africa,rough the expansion of semi-intensive, small-scale pond aquaculture. Nutrition and feeding play antral and essential role in the sustained development of aquaculture and, therefore, fertilizers anded resources continue to dominate aquaculture needs. This paper reviews a number of specific issuesthe fields of aquatic animal nutrition and feeding which are critical for sustainable aquaculture

oduction in both industrialized and developing countries, e.g.: nutrient requirements of fish and theirpply under practical farming conditions, availability and supply of feed resources and their implicationdevelopment of aquafeeds, forecasting of demand and supply of marine resources, and maintenanceenvironmental quality and sustainability of aquaculture systems. While discussing the nutrient

quirement of fish under farming conditions, the possibility of accessing existing databases on nutrientquirements is examined, along with their application for establishing general nutritional principles.rticular emphasis is placed on understanding the contribution of naturally available food in semi-tensive aquaculture and its role on the development of on-farm feed management strategy. Othersues such as nutritional effects on immunocompetence and disease resistance of fish, understanding

broodstock and larval nutrition, role of nutrition on fish quality, and development of regionaltritional databases for aquaculture development are also discussed. Recommendations forprovement of nutrition and feeding protocols in support of sustainable aquaculture development ine third millennium are also made.

EY WORDS:Aquaculture, Feeding, Aquafeeds, Nutrition.

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ntroduction

ver the last decade, spectacular growth hasken place in aquaculture. Most production inveloping countries is realized from pond-sed or open-water extensive, improvedtensive and semi-intensive practices usinglyculture farming technologies. In contrast,

e bulk of high-value freshwater and marinernivorous finfish in developed countries isoduced by intensive farming systems usinggh-cost nutrient inputs in the form ofutritionally-complete formulated diets.

is unequivocally agreed that global

Nutrient requirements and supplyunder practical farming conditions

Growth, health and reproduction of fish andother aquatic animals are primarily dependentupon an adequate supply of nutrient, both interms of quantity and quality, irrespective ofthe culture system in which they are grown.

Supply of inputs (feeds, fertilizers etc.) has tobe ensured so that the nutrients and energyrequirements of the species under cultivationare met and the production goals of the systemare achieved.

Complete data on nutrient requirements are


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uaculture production will continue tocrease, and much of the increased productiondeveloping countries of Asia and Africa is

ely to be achieved through the expansion ofmi-intensive, small-scale pond aquaculture.

utrition and feeding will play an essential rolethe sustained development of this

uaculture. Therefore, it is imperative thatrtilizers and feed resources continue to beoduced and refined. Sustained development

aquaculture, however, must take intocount and ensure that the needs ofmpeting users are met, and thatvironmental integrity is protected. Therefore,stainable aquaculture management shoulddress allocation of inputs based on localcumstances, and balance maximizingofitability with social and environmentalsts.

is paper will review a number of specific

sues in the fields of aquatic animal nutritiond feeding that are critical for sustainableuaculture production in both industrializedd developing countries. Some of the major

sues are:

availability and cost of feed resourcesand development of aquafeeds;increasing competition for resources withother users (e.g. agriculture andlivestock industries);forecasting of local and global marketsupply and demand; andmaintenance of environmental qualityand sustainability of aquaculturesystems.

uaculture development is also confrontedth the choice between using establishedlture of herbivorous/omnivorous speciesder extensive or semi-intensive systems orveloping more intensive systems to meetcreasing production demands. Similarly,sues and conflicts, such as the demand forod verses availability of marine resources,oductivity verses environmental quality, andoice of species verses biodiversity, warranttical examination.

only available for a limited number of species.Although dietary protein and lipid requirementsand carbohydrate utilization are relatively wellinvestigated for several fish and shrimpspecies, data on the requirements ofmicronutrients such as amino acids, fatty acidsand minerals are only available for the mostcommonly cultivated carnivorous and selectedomnivorous fish species. Available data onnutrient requirements for various fish species

are presented: protein (Tables 1 and 2), aminoacids (Table 3), essential fatty acids (Table 7),minerals (Table 8) and vitamins (Table 10).

Table 1 shows the protein and energy levelsresulting in maximum growth for a few speciesof juvenile fish. The data show that the proteinrequirements for different fish species rangefrom 28 to 56 percent of dry diets. Apparently,marine and freshwater carnivorous speciesrequire 40-55 percent dietary protein, while

most freshwater omnivorous and herbivorousspecies require 30-40 percent of their dry dietto be made up of protein. Like finfish, mostcrustaceans studied to date have rather highprotein requirements, ranging from 30 to 60percent of the dry diet (Table 2).

Lipids are primarily included in formulated dietto maximize their protein sparing. There isconvincing evidence that the degree ofunsaturation does not appreciably affectdigestibility or utilization of fats and oils asenergy sources for coldwater or warmwaterfish (Steffens, 1989). Carnivores like trouthave natural diets rich in triglycerides and canadapt to high fat diets (upper limits have yet tobe defined). Dietary lipid levels as high as 35percent has been reported in some salmonidfeeds (New, 1996). The maximum levels forother freshwater fish appear to be lower. Ingeneral, 10-20 percent of lipid in mostfreshwater fish diets gives optimal growth rates

without producing an excessively fatty carcass(Cowey and Sargent, 1979).

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rbohydrates are the leastpensive form of dietary energyd are frequently used for proteinaring in formulated diets. Fish

d shrimp vary in their ability togest carbohydrate effectivelyew, 1987). The utilization ofetary carbohydrate has also beenund to vary with the complexity

chemical structure of therbohydrate source used. Channel


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tfish (Ictalurus punctatus) andruma shrimp (Penaeus japonicus)pear to utilize complexrbohydrates more readily thanmple sugars (NRC, 1983; New,87) The ability of carnivorous fishecies to hydrolyse or digestmplex carbohydrate is limited duethe weak amylolytic activity in

eir digestive tract, thus for

ecies such as trout, starchgestion decreases as theoportion of dietary starch iscreased. For salmonids,rbohydrate digestibility alsominishes with increasingolecular weight (Steffens, 1989).

general, warmwater omnivorousherbivorous fish species such as

mmon carp, channel catfish and

l have been found to be moreerant of high dietaryrbohydrate levels. Furuichi andne (1980) compared thelization of carbohydrates bymmon carp, red seabream, andllowtail. Growth retardation andw feed efficiency were noticed inmmon carp fed diets containinger 40 percent dextrin, redabream fed over 30 percent

xtrin, and yellowtail fed over 20rcent dextrin. Studies of commonrp (Takeuchi et al., 1979) andannel catfish (Garling and Wilson,77) have shown thatrbohydrate levels up to about 25rcent of the diet are utilized asfectively as lipids as an energyurce.

studies on finfish to date have

own that they need the samesential amino acids as most otherimals (Table 3). Thequirements for individual aminoids are fairly consistent betweenecies, although variability isparent both between species andtween studies on the sameecies. A large part of theriability may be explained byfferences in the methods used by

rious workers. Luquet (1989)inted out the rather closereement between amino acidquirements for coldwater fishainbow trout) and those ofarmwater fish (channel catfish)hen expressed in absolute terms

Luquet (1989) further suggested that extensive research onthe determination of quantitative amino acid requirementsdoes not seem to be a priority, as indirect approachesprovide a rather accurate estimate of requirements. Table 4summarizes the range of essential amino acid requirementsthat have been determined for a variety of species of finfish.

Dietary lipids provide essential fatty acids (polyunsaturatedfatty acids, PUFAs) that fish, like all animals, cannotsynthesise but require for the maintenance of cellularfunction. Plant oils are generally rich sources of linoleic

series fatty acid (n-6) and with the exception of linseed,conopher seed and hempseed oils, contain little or nolinolenic series fatty acid (n-3) (New, 1987; Tacon, 1990;Table 5). Linolenic series fatty acids are found in terrestrialanimal fats only in trace amounts and are common only inmarine oils, highly unsaturated fatty acids HUFAs (20:5n-3,22:5n-3, 22:6n-3) are virtually restricted to this source(Steffens, 1989; Tacon, 1990; Table 6).

Dietary essential fatty acid (EFA) requirements of the mostcommonly cultivated fish species are presented in Table 7.


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d not as the percentage of theotein content.

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is apparent from this table that marine fishe. red seabream, sea bass, yellowtail, turbot,aice) have exclusive requirement for HUFAs0:5n-3 and 22:6n-3), while freshwater oradromous species require a higheroportion of C18 fatty acids within the n-3ries.

general, coldwater freshwater (i.e.lmonids, ayu) fish have an exclusive

All fish studied to date appear to require EFA(n-3 or n-6) at about one to two percent of thediet by dry weight. At present, there is no firmquantitative information on the dietary EFArequirement of marine shrimp or freshwaterprawns. The information available at present ismore suggestive than conclusive, however, aswith fish, it is believed that n-3 series fattyacids have a higher EFA activity than n-6 seriesfatty acids in shrimp and prawn (NRC, 1983;


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quirement of n-3 series PUFA (18:3n-3,:5n-3, 22:6n-3) in their diet, while

armwater freshwater fish require both n-3ries and n-6 series PUFA (i.e.carps, eel) ore n-3 or n-6 series (tilapia).

Tacon, 1990).

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etermination of dietary mineralquirement of aquatic animals hasen complicated by the fact that theyve the ability to absorb minerals

om the surrounding water in additionthe food ingested. The dietary

quirement of a fish and shrimpecies for a particular element thuspends to a large extent upon the

ncentration of the element in theater body (Steffens, 1989; Hepher,90). At present, there is little

formation concerning thentribution of waterborne elements toe total mineral balance of fish orrimp. Further, aquatic animalssorption of minerals is largelyfluenced by variations in response tolt regulation or osmotic pressure. Asresult, freshwater fish have greatermands for adequate mineralpplies than marine fish and shrimp.

nerals available in feed ingredientse not always sufficient to meet thehs requirements. Some of thenerals may be leached during theocessing of the food (Hepher, 1990).oreover, many of the feedgredients may be rich in particularnerals and deficient in others, or

ly partially available to the animalnsumers. Dietary mineralquirements of five fish species areesented in Table 8. However, theformation on mineral requirement ist complete and sometimes highlyriable. Cho and Schell (1980,apted from Hepher, 1990)mmarized the requirement of 16nerals (Table 9) for fish. Apparentlye summary was prepared fromailable data for different fish speciesd should thus be considered asggestive. Since much of the mineralquirement is supplied by the food,rtial mineral supplementation maysufficient to meet dietary needs.

(De Silva and Anderson, 1995). As a result, the dataobtained from studies of salmonids, common carp orchannel catfish (Table 10) are usually applied to otherspecies while formulating the complete diet for intensiveculture. While natural food is usually rich in vitamins, thismay not be the case with supplementary feed. Vitamindeficiency mainly appears, therefore, in intensive culturesystems, where supplementary feed is the major, if notthe only, source of feed (Hepher, 1990) or where

formulated complete feed is the only source of feed.

Given the large variety of species under culture, it is notpractical to undertake extensive studies on nutrientrequirements and utilization of each species. If wecritically examine the existing database on the nutrientrequirements of different fish species, a tolerablegeneralization of nutritional requirement for differentspecies groups can be made. The available literatureindicates that the some of the nutrient requirements ofmajor cultivable fish species can be generalized into four

broad groups:

marine carnivores (e.g. yellowtail, red seabream,sea bass, salmon, trout, grouper);freshwater carnivores (e.g. snakehead, eel, goby);freshwater omnivores (e.g. tilapia, catfish, commoncarp, Indian major carps, shrimp); andfreshwater herbivores (e.g. grass carp, silver carp).


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though the pathologies related toamin deficiency in fish are well

vestigated, quantitative dietaryamin requirements of fish anduatic animals are probably the leastudied area in fish nutrition. Theamin requirements of the majorityspecies of fish in culture have noten determined

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e nutrient requirements shared amongfferent species generally include protein,id, amino acid and water-soluble vitamins.rther, carbohydrate utilization by closelyated species or species groups falls within arrow range. Similarly, the differences in thequirements of most of the micronutrients,ch as amino acids, vitamins, minerals andtty acids show marginal variation betweenltured species (De Silva and Anderson,95).

Therefore, general nutritional principles can beapplied, and reliable data from closely relatedspecies can be utilized as and whenappropriate. The use of such nutritionalstrategies will strengthen sustainability of theproduction system as a whole.

A large proportion of aquaculture in manydeveloping countries is carried out in rural

areas, where farmers adopt extendedextensive or semi-intensive farming practices.

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though information concerning the nutritionalquirement of many of these cultivated fishecies is well established, most has been

nerated from laboratory-based controllededing trials and, hence, is useful mainly fore formulation/production of nutritionallymplete feeds for intensive culture systems.ch data may be less applicable to farmingnditions where nutrition is from natural foodpplies or supplemental artificial feeds.tural productivity of the water bodynerally plays an important role in theseoduction processes.

Nutrition and feeding of finfish and crustaceansin semi-intensive pond-farming systems arecomplex and poorly understood. Little or no

information exists on the dietary requirementsunder farming conditions for many of thespecies cultured. To a large extent, this is dueto the difficulties of quantifying the contributionof naturally available food organisms to theoverall nutritional budget of pond-raised finfishor crustaceans (Tacon, 1993). In order tomaximize cultivation production, there is anongoing need to develop basic understandingof nutrient dynamics, specifically the role offertilization and natural productivity.

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ch under-standing will allow us tosure that cost-effective diets areveloped that take into accounttritional requirement differences

tween species, natural productivity ofe water bodies and the location-specificailability of inputs.

ere is evidence that even minorodifications of different inputs into semi-tensive systems can bring about majoranges in terms of growth, reproductiverformance and overall productivity ofe system (De Silva and Davy, 1992;erina et al., 1993; Bjerkan, 1996; Tacon

d De Silva, 1997; Miaje et al., 1999).nce feed and fertilizers represent about-80 percent of the total cost ofuaculture production, understandinged management strategies and theirplementation is of major importance.

Method of feed presentation, feeding rates andfrequency are three areas where much improvement


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though there are many examples of howproved feeding strategies can beccessfully implemented using simpledigenous techniques (Tacon and Deva, 1997), further studies and researche necessary.

can be made. In many semi-intensive systems,supplementary feeding is based on fish biomass.Environmental factors and natural foods, which areknown to influence food consumption and fishgrowth, are seldom considered. In addition, noprecise schedule(s) or table(s) for most cultured fishare available.

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eding rates or ration size need to betermined by pond ecology (which variesnsiderably with season), in addition to fishomass. Maximum benefits from supplemental

In most semi-intensive systems, particularlysmall-scale rural operations, supplementalfeeds are dispensed in powdered form (DeSilva, 1993). There is increasing doubt about


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eding can only achieved if the diet is ingestedits entirety, and supplied to fish or shrimp atrate compatible with the quantity and qualitynatural food available in the pond. It has

ten been advocated that feeding regimesould reflect the feeding habit of the speciesder wild conditions (Tacon, 1993). Theajority of feeding tables recommended byed manufacturers for use within semi-tensive farming systems are hypothetical and

t irrespective of dietary composition, pondrtilization rate, natural food availability,ocking density and standing crop (Tacon,93). The benefits of increasing feeding

equency have also been well documentedlalon, 1991; Sumundra, 1992). Thesethors reported reduced leaching and feed

ss, improved growth and feed efficiency forrimp through increased feeding frequency.ble 11 presents a summary of experimentalta available on feeding frequencies at which

timal growth was observed in different finfishecies. The variability in the feedingequencies shown in the table is probablyore indicative of uncertainty of results, ratheran of the biological variability per se (Deva and Anderson, 1995). Nevertheless, it

mphasises the importance of feedingequency in aquaculture. The optimum feedingte and frequency of presentation must,erefore, be determined for individual feedsd farms by carefully monitoring feed

nsumption, growth and feed efficiency oververal growing seasons (Tacon, 1993).

the efficiency of this form of feeding, sincethere appears to be significant wastage andindividual fish face difficulties ingestingsufficient quantities of each of the constituentingredients to obtain a nutritionally balancedmeal. In cyprinid polyculture, farmers oftenuse feeding bags, which are suspended at anumber of locations, the perforated bottomtouching the water surface (Tacon and DeSilva, 1997) to increase the feeding efficiency.

Although there has been no scientificevaluation of the efficacy of this feedingmethod, most farmers believe the returns arehigher than with hand broadcasting.

Similar but somewhat modified feedingmethods are used by the farmers of AndhraPradesh in India. They keep the powdered feedmixture in perforated polyethylene bagssuspended by wooden poles at a number ofpoints around their ponds. Fish browse on the

feed through the perforations and within two tothree hours most of the feed in the bag isutilized. This method results in minimumwastage of feed and helps the farmers to applymedication effectively through feed (Veerina etal., 1993). In carp farming systems inBangladesh, supplemental feeds are dispensedin both wet dough balls and in powdered drymixture form. More recently, Miaje et al.(1999) demonstrated that both pelleted anddough forms of supplemental feed, comprised

of mustard oil cake, rice bran and wheat bran,appear to be more suitable than powdered feedfor Indian major carps and Java barb inpolyculture.

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veral other supplementary feedingchniques, ranging from manual feeding byacing floating feed items into a floating ored-surface bamboo frame to simple demandeders, are practised in different parts of theorld. However, in many cases, hard data arecking on the efficiency of these feedingchniques (Tacon and De Silva, 1997). Inmi-intensive aquaculture, there is a need forrther research in these directions.

veral other techniques have been reported toaximize use of supplementary feed in semi-tensive farming systems. De Silva (1985)vocated the adoption of a mixed feedinghedule with alternate high and low proteinets. Adoption of such mixed feeding

Thus although these studies have generated asignificant amount of information on pathologyin relation to nutrient imbalance and thepresence of toxic and antinutritional factors infeed ingredients, the possible effects of macro-and micronutrients on immunologicalparameters have mainly been overlooked.Nutrition and farm management strategies playcritical roles in fish health and diseaseoutbreaks within intensive farming systemsand, to lesser extent, in semi-intensive farmingsystems (Tacon, 1997a). However, it must beemphasized that nutrition and farmmanagement should not only satisfy thedietary nutrient requirements of the farmedspecies for maximum growth but also forincreased immunocompetence and disease


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chniques using feeds already availablepears more cost effective and feasible thanveloping new feeds (De Silva, 1993).rthermore, protein-rich diets (morepensive) diluted with carbohydrate-rich diets

ess expensive) (Hepher and Pruginin, 1981)well as use of a limited number of diets withproved nutritional value (Hepher, 1990;magaysay et al., 1990) may offer significantonomic advantage by reducing the overall

ed cost in intensive aquaculture practices.

utrition and health

large number of research studies have beenrried out to quantify the nutrientquirements of fish and shellfish (Alliot et al.,74; Jauncey, 1982; Daniel and Robinson,86; Akand et al., 1989, 1991a,b); De Silvaal., 1989; Borlongan and Parazo 1991; Ellis

d Reigh, 1991; Borlongan, 1992; Koshio et, 1993; Castell et al., 1994; Habib et al.,94; Hasan et al., 1994; Mourente et al.,95; Querijero et al., 1997; Hossain andruichi, 1999, 2000; Ngamsnae et al., 1999).other area of research that has received

gnificant attention in aquaculture nutrition ise use of plant and animal by-products ashmeal substitutes in fish feed (Atack et al.,79; Dabrowski and Kozak, 1979; Higgs et, 1979; Capper et al., 1982; Jackson et al.,

82; Tacon et al., 1984; Wee and Wang,87; Davies et al., 1989; Wee and Shu, 1989;wler, 1990; Gallagher, 1994; Kaushik et al.,95; Habib and Hasan, 1995; Stickney et al.,96; Brunson et al., 1997; Hasan et al.97a, b) Unfortunately, the major emphasis ofese studies was on optimizing growth, feedficiency and general health condition.

resistance. There is a growing need to takeimmunological parameters into account innutritional studies on aquatic animals. This isespecially important, since fish appear todepend more heavily on non specific defencemechanisms than mammals (Kaushik, 2000).

The effects of vitamins C and E are welldocumented, but several other nutrients andfeed additives, including other vitamins(vitamin A), trace elements (Zn, Cu, Se, Mn,Fl), essential fatty acids and carotenoids havealso been reported to play important roles inthe immune response of fish (Devresse et al.,1997). While the application of vitamins,essential fatty acids and other micronutrientshas shown conclusive evidence of a role insustaining the immune function of fish inlaboratory trials and in intensive commercialaquaculture operations, their influence on thedefence mechanisms of fish reared under semi-

intensive culture conditions (where ecologicalfactors also influence diet) remains to bedetermined. It is perceived that natural foodproduction in semi-intensive culture conditionsshould supply enough of these nutrients tomeet the fish immune response requirements(Dickson, 1987; Castell et al., 1988; Castilleand Lawrence, 1989; Hepher, 1990; Trino etal., 1992; Tacon, 1993).

In recent years, probiotics (non pathogenic,opportunistic bacteria of the genera Bacillus,Lactobacillus, Streptococcus) and naturalimmunostimulants (yeast, glucans) haveshown promise for increasing diseaseresistance in fish and shellfish. As a result,there has been a growing interest in the use ofimmunostimulants as prophylactic agents tominimize the risk of disease outbreaks. Thelarge number of commercial immunostimulantson the market clearly reflects this interest;however, the results obtained to date have not

always been consistent and these products arestill less effective than vaccines (Devresse etal., 1997).

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ere is, therefore, a clear need to improve the

ability of immunostimulants, micronutrientsd oral vaccines, especially under subtropicald tropical culture conditions, as well astritional information related to effective use

vaccines and/or chemotherapy, beforeopting new immunostimulation techniques

Recent work on salmonids showed that product

quality can be tailored by modifying the dietarycomposition, and a more nutritious fillet can beproduced (Kaushik, 2000). However, moreresearch has to be done on this field, givingadequate consideration not only to nutrientbioavailability but also to postharvest quality


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all pers. comm). Further, improving healthrough proper nutrition would not only reducee need for chemotherapeutants, but also helpoid major disease outbreaks.

xic and antinutritional factors (blockingfective nutrient assimilation) present in plantgredients, nutritional imbalances ofrmulated feed, adventitious toxic factors andxic compounds formed during feed storaged processing etc., can all severely affect thealth status of cultured species and lead tocreased susceptibility to disease. Althoughformation on these aspects is documented,d appropriate precautions during feedrmulation and processing can minimize thek (Devresse et al., 1997; Lall pers. comm),ere is a need for further research to developtter strategies to minimize such toxicityfects.

utrition and fish quality

sh is a highly nutritious food, containing highmounts of proteins with high biochemicallue for humans. In addition, it is a very goodurce of polyunsaturated fatty acids (PUFA)own to be beneficial in preventingrdiovascular diseases, breast and colonncer, psoriasis etc. (Kaushik, 2000). Highlysaturated fatty acids (HUFA) present in

arine fish oil are medically proven to beneficial against inflammatory disorders andchaemic heart disease by modifyingachidonic acid/prostaglandin pathwaysargent, 1992). Fish also containcronutrients such as iodine, selenium andt-soluble vitamins (A and D) that havesitive effects on human health. In manyveloping countries of the world, small fishe eaten whole and thus contribute calcium,osphorus and iron to the human diet.

mprovement of feed and nutrition inuaculture may give us the opportunity torther improve the nutritional quality andnefits of the fish consumed. Nutritionallue, colour and appearance, smell and taste,xture and storing capacity may all be affected

the quality of nutrition and feed providedring culture.

control.

Aquafeed and the environment

Given that feed is the biggest source ofnutrient loading in fish and shrimp aquacultureproduction, clear understanding of its impact isessential for sustainable development, eitherintensive or semi-intensive. This will help

reduce negative impacts and improvepredictability of environmental effects. Presentknowledge and understanding of theenvironmental impacts of aquafeed needsfurther refinement; however, it is generallyacknowledged that these impacts can bereduced by feeding fish with moreenvironmentally friendly diets, developingbetter feeding strategies and by a sound farmmanagement. Interrelationships among variousfactors and strategies in dealing with

environmental pollution and aquafeed areschematically shown by De Silva and Anderson(1995). The authors advocated a holisticapproach and noted that fish nutritionists canno longer be formulators of nutritionallywholesome diets, but need to consider freshstrategies in diet development and feed costreduction.

In developed countries, where intensivefarming of carnivorous fish species is primarily

dependent on a supply of nutritionallycomplete, formulated diet, mitigation ofnegative impacts of aquafeed throughdevelopment of more environmentally friendlydiets is considered to be a major challenge.Potential pollutants from aquafeed arephosphorus and nitrogen, as well as organicmatter. Alvarado (1997) describes the flux ofnutrients from a gilthead seabream farm,where fish under intensive production were fedcommercially extruded bream diets (Fig. 1). It

was shown that 180 kg of solids, 13 kgphosphorus and 105.4 kg of nitrogen werereleased to the environment through excretionand by uneaten feed to produce 1000 kg offish. Thus lowering the amount of nitrogen andphosphorus in feed as far as possible will beone of the most efficient ways to reducepollution effects.

Further, more environmentally friendly dietscan be produced by developing diets with

reduced food conversion ratios (FCR), e.g. byimproving palatability and digestibility of rawingredients.


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6

e precise requirements for protein, aminoid and energy for each species and stage ofvelopment, as well as strain, need to befined. It is also acknowledged that nutrientquirements change as the intensity of culture

anges. The digestibility of nutrients is notecisely defined in many commercial feeds,d current research shows that feedrformances and digestibility can be increasedth the use of enzymes that enhance plantotein use, and by use of extrusionchnology. Therefore, continued research onocessing techniques and additives andzymes for improving feed performances andgestibility are required, for example, ontimization of protein/energy ratios and amino

id profiles to reduce nitrogen excretion.

mproved knowledge of feeding strategies hasso helped improve feed utilization and reducee FCR and waste, thereby reducing negativevironmental impacts (Alvarado, 1997).amples of improved feeding strategies range

om:

sophisticated computer-controlledfeeding devices for intensive commercialproduction of high value marine fish;increased feeding frequency;adjustment of feeding rate based on

pond productivity; anduse of supplemental feed in pelleted ordough form, as opposed to powderedform, in semi-intensive aquaculturesystems.

In addition to the potential for environmentaldegradation by waste aquafeed, therapeutantmisuse should not be overlooked. Medicatedfeeds are often used indiscriminately duringdisease outbreaks in hatcheries, nurseries and

farms (Hasan and Ahmed, 2001). Althoughsome of these drugs are unstable in water anddo not cause any major problem, others arevery stable and can precipitate development ofbacterial strains that are resistant to thesedrugs. Furthermore, use of multiple, related,drugs can result in development of bacterialstrains that are highly resistant to a wide rangeof drugs (Alvarado, 1997).


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us several factors and strategies have to berefully monitored, and alternative strategiesveloped, while dealing with aquafeed and

vironmental pollution.

roodstock and larval nutrition

is well recognized that adequate nutritions an important role to play in the

Some interesting short-term effects ofnutrients on broodstock have also beendescribed in red seabream. It has been

reported that specialized diets givenimmediately prior to, or during, spawning ofred seabream affected the composition of theeggs. Pigments such as -carotene,canthaxanthin or astaxanthin resulted inmarked improvement in the percentage ofbuoyant eggs. Therefore, there is a need to


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productive success of all animals, includingh. There are a number of aspects ofproduction that can be affected by nutritionalatus:

the time of first maturity;the number of eggs produced(fecundity);egg size; andegg quality as measured by chemicalcomposition, hatchability and larvalsurvival (De Silva and Anderson, 1995).

uring the last decade, increased attention hasen paid to the role of different componentsbroodstock diets. It has been shown that

sential fatty acids, vitamins (A, E and C),ace minerals, -carotene and other carotenoidsn affect fecundity, egg quality, hatchabilityd larval quality (Kaushik, 1993; De Silva andderson, 1995; Izquierdo and Fernandez-lacios, 1997), and that the amino acidquirements of broodstock are apparentlymilar to those for optimal growth (De Silvad Anderson, 1995). Results of these studies

so indicate that there exists great speciesversity in nutritional requirements affectingproduction. Apart from common carp, most

these studies have been carried out forarine carnivorous fish species (De Silva andderson, 1995; Izquierdo and Fernandez-lacios, 1997); thus relatively little is knownout broodstock nutrition of freshwater

mnivorous/herbivorous fish species.erefore, there is an immediate need to learnout the nutritional requirements foroodstock maintenance and reproduction forost of the commercially important freshwaterh species. Clearly defined broodstocktrition is not only necessary for high-valueh cultivated under intensive aquaculture, butuld also significantly enhance productionccess of species grown under semi-intensive

rming conditions. Another aspect that hasceived little attention to date is the nutritionmale broodstock. Possible improvement of

erm quality through dietary manipulationserves further consideration.

a study continued over a period of eightonths prior to spawning, Watanabe et al.984a) found that EFA (n-3 PUFA)-deficientets in red seabream produced eggs withgnificantly lower survival and high levels ofrval deformity.

define different stages of broodstock nutritionfor appropriate management. Nutritionalrequirements of broodstock can further differdepending upon the phase of reproductiveperiod. These periods are generallydistinguished as:

the period from commercial size tobroodstock size;immediately prior to, or during,spawning; andpost-spawning.

Formulation of complete diets should,therefore, take into account the stage-specific,as well as species-specific nutritionalrequirements of the broodstock. Nutritionistsand the feed industry should also consider theoptions for developing three types ofbroodstock diets:

conditioning diet,

reproduction diet, andrecovery/maintenance diet.

The broodstock conditioning diet should beformulated as an optimized growout diet tomeet the full nutritional requirements of thespecies from commercial to broodstock size inmaximal synergy with the environment. Thereproduction diet used before or duringspawning should meet the needs for maximalreproductive performance (spawning success

and fecundity), gamete quality, and verticaltransfer of nutrients and biologically activesubstances to offspring. Therecovery/maintenance diet should assistrecovery from reproductive exhaustion andreconditioning for the next reproductive cycle.

The nutrient requirements of all animals varythroughout their life cycle. Complexmorphological and physiological changesinvariably modify feeding and nutritional

requirements. Finfish, nutrition during theembryonic stage is provided by the yolk sacand oil globules. The transition from anendogenous to an exogenous food supply,which marks the onset of the larval stage, isone of the most critical phases of the lifecycleand is the period when much of the mortalityof hatchery-reared stock occurs (De Silva andAnderson, 1995). In spite of the clearimportance of nutrition in influencing thesurvival, growth and development of larvae,

however, relatively little is known about theabsolute nutrient requirements of these stagesof aquatic animals.


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8

is generally acknowledged that the feedinghaviour of larvae has a dominant role inrval nutrition, e.g. the larvae of many fishecies will not take an artificial diet. There areso species that will take an artificial diet, buts must be supplemented with liveoplankton to satisfy all nutritionalquirements. In some species, provision ofcroparticulate diets in addition to live foodhances both growth and survival ratesanazawa, 1991a).

recent years, a considerable amount ofsearch has been devoted to study of thetritional requirements of marine fish larvae.mparison of the biochemical composition ofgs and larvae at different stages, pattern ofss and conservation of nutrients duringarvation and feeding experiments that controle-prey or microdiet nutrient composition areme of the most frequently used methods toudy nutritional requirements of marine fishrvae (Izquierdo and Fernandez-Palacios,97). Live foods constitute the main diet forarine fish larvae, but a single live foodecies is often unable to satisfy the completetritional requirement of the species underlture. Since many finfish are reared on a

ngle type of live food at any one time, amber of studies have been conducted to

vestigate the effect of enriching live foodganisms with various nutrients. Resultsdicate that larval fish require diets with a highotein content (Kanazawa, 1991b, Kissil,91; Cho and Cowey, 1991; Luquet, 1991)d sufficient amounts of essential fatty acidsavens et al., 1991). The live foods that haveen most intensively investigated, with

spect to their nutritive suitability are brinerimp (Artemia spp.) and rotifer (Brachionuscatilis). Artemia is low in the essential fattyids eicosapentaenoic acid (C20:5n-3, EPA)d docosahexaenoic acid (C22:6n-3, DHA);us simple methods of bioencapsulation haveen developed to incorporate particulateoducts into brine shrimp nauplii. The naupliinsume particles of a desired compositionor to being offered as prey for fish larvae.e nutritive value of rotifers is made suitable

culturing them a suitable medium such as -ast, and by feeding with a mixture ofmogenized lipids and bakers yeast or marine

ga (Chlorella spp.), all of which are rich in n-3lyunsaturated fatty acids. While it isnerally considered that eicosapentaenoic andcosahexaenoic acids are important fatty

Culture of most marine fish and shrimp larvae,at least during early ontogenesis, still reliesheavily on the supply of live food items (brineshrimp, rotifers and microalgae). Thisdependence on live food is already causingconcern, due to the lack of resources andincreasing production costs. Efforts areunderway to find alternatives, such as othersources of live prey, partialreplacement/supplement of live prey anddevelopment of microparticulate diets forlarvae. Much research effort is also beinginvested in establishing nutritional limitingfactors, early use of artificial diets andreduction of the weaning period, for manymarine fish larvae (Alami-Durante and Meyers,

1993; De Silva and Anderson, 1995; P. Lavenspers. comm.)

For most hatchery-reared marine andfreshwater fish and shrimp larvae,development of complete artificial diets forrearing, or reduction of length of weaning fromlive food, is of immense importance for furtherdevelopment of aquaculture of these species.Determination of absolute nutrientrequirements of fish larvae of commercialimportance is also an essential prerequisitebefore any attempt is undertaken toformulate/develop an artificial diet. Thenecessity to utilize diets with optimum stabilityand good physical characteristics in water,along with enhanced attractability, are clearlyrecognized. Attractiveness is an especiallycritical factor for optimum ingestion of the dietand is a crucial component for accurateevaluation of the nutritional value of theparticular formulation. Other aspects that need

to be addressed for the development of larvaldiets are improvement of digestibility ofmicroparticles and diet quality through supplyof requisite nutrients, e.g. exogenous digestiveenzymes. Another approach is incorporation offeeding stimulants, especially amino acids, todry diets. Research on the physical behaviourof particles in the water column and controlledleaching of components also deserves furtherattention. Although much of the potential formanipulation of natural productivity to ensure

production of good quality larvae under semi-intensive farming systems remains to bedetermined (Kaushik, 2000), the problemsassociated with nutrient quality of live food donot necessarily occur when larvae are rearedunder natural pond conditions. For example,where planktonic growth is stimulated by


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ids in the nutrition of larval fish, the specifictty acids required vary between species (Deva and Anderson, 1995).

fertilization/natural productivity, as in the caseof rearing of Chinese carps (De Silva andAnderson, 1995), the range and suitability ofnatural foods enable the cultured organisms toobtain all nutrient requirements without furthersupplement.

209

emand and supply of marineesources for aquafeeds

is envisaged that world annual fishmealoduction will remain static at 6.5 million mter the next decade. World annual fish oiloduction will remain around 1.24 million mtring next decade, although this is expectedfluctuate due to El Nio. To keep pace with

obal aquaculture production, a markedcrease in use and production of formulateded is foreseen for the next 25 years (Tablesand 13, Fig. 2) (Barlow, 2000). High quality

hmeal and fish oil are the major dietarygredients for the production of formulateded. It is, therefore, predicted that thequirement for these will increase from 2,1153,262 million mt for fishmeal and from 0,7081,308 million tonnes for fish oil between

00 and 2025, to support todays intensiveuaculture industry (Table 14, Figs. 3 and 4)arlow, 2000).

hile the demand for fishmeal for theuaculture industry will increase, it isojected that there will be a drastic reductionthe use of fishmeal for the poultry industryarlow, 2000) (Fig. 4) and, as a result,uaculture will have sufficient fishmeal to20 and beyond. It is also predicted thatfficient fish oil will be available to year 2010,hough fluctuations caused during El Nioay create temporary shortages. However,yond this period, there will be a shortfall ofarine oil for aquaculture feed (Table 14, Fig..

Since marine fish oil is rich in n-3 PUFA and themajor source of unsaturated fatty acids incompound aquafeeds - an essential dietarynutrient for all marine carnivorous finfish andcrustacean species (NRC, 1993) - the feedindustry should look for possiblesubstitutes.The demand for fish oil could bereduced by using vegetable oil or a blend of

fish oil and vegetable oil as a source ofunsaturated fatty acids (n-3 and n-6). With theexception of strictly carnivorous fish species,fish are able to use C18:2n-6 or C18:3n-3 andconvert them into corresponding HUFA:C20:4n-6 in the case of n-6 series, andC20:5n-3 or C22:6n-3 in case of n-3 series.Gene research on marine carnivorous fish toacquire the capability to elongate C18:3n-3deserves further consideration (see Dunham etal., this volume).

Alternative protein sources: plantand animal by-products

Fishmeal and fish oil are the most widely useddietary components of commercially producedhigh quality fish/shrimp feed throughout theworld. Fishmeal and oil are preferred forcommercial feed production because of their

unique balance of protein (amino acids) andlipids (long chain n-3) in a highly digestibleenergy dense form. Substitution with otheringredients, especially those of plant origin, islikely to compromise nutrient balance and failto match the energy concentrations achievedusing fishmeal and oil. Nevertheless, the highcosts of these ingre-dients have severelyrestricted their use, especially in semi-intensiveaquaculture systems.


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0

ricultural (animal and plant) by-productsd wastes of agro-processing industriese widely available in most parts of theorld and many are traditionally used ased for farm animals. Of these (Table 15),e major conventional feed ingredientsed as protein and energy supplements for

h, to date, are:

meat meal, meat and bone meal mix,poultry by-product meal, blood meal(animal origin); andoilseed cakes, pulses, cereals andcereal by-products (plant origin).

nsidering the increasing cost of fishmeald doubt concerning its long-termailability, much research has been carried

t on the use of plant and animal by-oducts as fishmeal substitutes (Dabrowskid Kozak, 1979; Jackson et al., 1982;con et al., 1984; Wee and Wang, 1987;

avies et al., 1989; Fowler, 1990;allagher, 1994; Kaushik et al., 1995;ickney et al., 1996; Brunson et al., 1997;san et al. 1997a). Although some animal-products have shown similar nutritionallues to those of fish meal for many fishecies, it is generally felt that there is

rrently no realistic alternative to fish mealfish oil, because of the high levels of highality protein and lipid required forltivation of the fast growing carnivoroush species. Replacement of fishmeal withant by-products does not generallyhieve the desired level of growth and

Lower performances are attributed to toxic andnutrient-uptake blockers in plant ingredients andthe inherent essential amino acid deficiencies ofmost plant proteins (Kaushik, 1989; NRC, 1993;Hasan et al., 1997b; Tacon, 1997b). Nevertheless,opportunities exist for use of these by-products asfish meal for most fish and shrimp grown in less

intensive systems.

Considering the improved extensive and semi-intensive farming systems practised by most small-scale fish farmers of Asia and other developingcountries, where fish and other aquatic animals areable to fulfill part of their nutritional requirementsfrom naturally available food in the system (Tacon,1993), ingredient quality similar to that of fishmeal is probably not necessary for most farmers.


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her performances required for culture ofh and other aquatic animals (Higgs et al.,79; Tacon et al., 1984; Stickney et al.,96; Alexis, 1997; Brunson et al., 1997;con, 1997b).

211


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2

nutritional composition (quantity,quality and bioavailability ofprotein, lipid, carbohydrate,vitamin and mineral) of feedingredients;their suitability for incorporation

into practical diets; andresults of experimental work onthe use of these ingredients infish feed.

Further, there is evidence that the useof many of these ingredients can beenhanced by simple processingtechniques. For example, cooked starchis more useful to many omnivorous andherbivorous fish than raw starch. Many

shrimp farmers in Andhra Pradesh,India cook their ingredients before use.Cooking has been reported to increasethe digestibility and increase feedefficiency (Hasan and Amin, 1997). Soinformation on simple processingtechniques and palatability to the


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ore relevant research emphasis would be on theppropriate utilization of these ingredients aspplemental feed rather than evaluation of thesegredients as fishmeal substitutes (De Silva, 1993,99). Improved information is needed on:

target species, along with storage andpreservation, seasonal and regionalvariability in proximate compositionetc., will all lead to more efficientutilization of these feed ingredients.

In contrast to semi-intensiveaquaculture practices, demands for fishmeal and agricultural by-products ofhigh quality are expected to increase,keeping pace with the dynamicdevelopments in intensive aquacultureof carnivorous fish species inindustrialized countries of the world.This will require greater availability ofquality feeds. Quality of alternativeprotein/energy sources, be it animal orplant, has to be ensured by appropriateevaluation and screening, starting fromsafe and careful collection, processingusing optimum technologies and

maintaining efficient quality controlsystems. Likewise, consumers expecteffective tracking and safety controlsystems in their final choice of foods.

Mention may be made about thespread of bovine spongiformencephalopathy (BSE), the dreadedmad cow disease. The World HealthOrganization (WHO) has recentlyconcluded that BSE may be spreadingworldwide through international tradein animal feed. Meat and bone meal aretwo of the animal by-product mealswidely used as fishmeal substitutes forfish farming in different parts of theworld. It is, therefore, imperative thatproduction, sale and use of all plantand animal by-products be based onsound science, true documentation,realistic risk analyses and clearlabelling, to ensure food safety.

Appropriate documentation and clearlabelling will also improve consumerconfidence and freedom of choice.

Development of regionaldatabase for aquaculturedevelopment

The costs of feed ingredients and farm

input are increasing, while marketcosts for the major cultivated finfishand crustacean species have remainedstatic or are decreasing.


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213

is, therefore, likely that increaseduaculture production will be fromrbivorous/omnivorous aquatic animals inveloping countries of Asia and other parts ofe world. Aquaculturists could reduce currentpendence on natural marine resources torm carnivorous finfish and marine shrimprough the use of low-cost, locally available,ernative feed ingredients. Research into thepropriate utilization of these feedpplements in semi-intensive aquaculture,wever, is still required. There is littleformation on their availability and abundance,pecially in many developing countries. Indition, development of intensive poultry,iry and other livestock industries is likely to

tensify the competition for nutrients and feedsources. A reliable database of agriculturaled resources is thus an essential prerequisiter planning sustainable aquaculturevelopment. A national agricultural feedrvey would create a database of feedsources and enable national aquaculturevelopment strategy planning. Further, thetablishment and/or strengthening of nationald regional fertilizer and feed ingredienttabases, and information systems, will

able projection of major agricultural by-oducts throughout the world that may benefite aquaculture feed industry.

onclusions

ver the last decade, the world has witnessedectacular growth in the aquaculturedustries of many developing countries. As asult, aquaculture has been contributing

gnificantly to food security and povertyeviation. It is anticipated that globaluaculture production will continue to increased further contribute to these needs. Nutritiond feeding play a central role in sustainableuaculture and, therefore, fertilizers and feedsources continue to dominate aquacultureeds. Much of the increased aquacultureoduction in developing countries of Asia andrica will likely be achieved through expansion

semi-intensive, small-scale pond culture,

us feed and fertilizer resource availability, asell as cost, could be the major bottlenecks forch development.

intensive aquaculture of marine carnivorousecies, fish meal and fish oil will continue to

the major ingredients in the near future,

Recognizing the current importance of fishmeal and fish oil within industriallycompounded aquafeeds, while lack of fish mealis not foreseen in the next 25 years, there is arisk that a lack of marine oils may occur in theshort term (5-10 years). With the expansion ofintensive aquaculture, aquaculturists mustcarefully assess the impact of nutrient loadingin the aquatic environment and use bothscience and judgement for reducing suchimpacts. Furthermore, a careful balancebetween environment, health/diseaseresistance and feed use should be maintained,so that the system does not deteriorate andnegatively impact market value and consumerconfidence.

Use of formulated feed and fishmeal has noclear future in semi-intensive aquaculture indeveloping countries of the world.Nevertheless, further intensification ofcommercial aquaculture will take place, even indeveloping countries, for shrimp andcarnivorous freshwater species, with the samepotential as mentioned above for an overallshortage of conventional feed ingredients.Alternative feed ingredients should be soughtat the same time as improvement of pondmanagement and manipulation of pondproductivity. Use of nutritionally completeformulated diets will, however, continue to playa dominant role in hatchery and nurseryproduction.

Recommendations

Improvement of nutrition and feeding for

sustainable aquaculture development can beachieved thorough:

increased understanding of the dietarynutrient requirements of culturedspecies, including their application topractical culture conditions;developing species-specific broodstockdiets that allow complete domesticationand maximal reproductive and larvalquality;

better understanding of larval nutritionalrequirements, in order to developsuitable compound diets, which willfurther reduce the need for live food;improving the understanding of theaquaculture farming systems (extensive,semi-intensive or intensive; closed or


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hough there may be scope for some use ofimal by-products as alternative proteinurces.

open culture systems) and the potentialnutrient loads and losses to theenvironment, to maximize nutrientretention efficiency;understanding and monitoring thedynamics of nutrient flows and sinkswithin pond-based farming systems;

4

improving the efficiency of resource usein aquaculture through use of appropriateagricultural and fishery by-products/wastes and nonfood-grade feedmaterials;developing feeding strategies based on

renewable feed ingredient sources whereproduction can keep pace with thegrowth of the sector;better understanding of nutrient bio-availability and interactions of commonlyused feed ingredients;better understanding of nutrientmodulation of disease resistance;improved strategies to minimize toxicityof nutrients and other compounds of feedorigin;

promotion of good aquaculture feedmanufacturing practice and good on-farm feed management;recognizing the importance of feed andconsumer concerns over food safetyissues (irrespective of the culturesystem), including the need fortraceability of feed materials andproduction methods; andconsidering the effect of diet on productquality and the positive nutritional

characteristics of the final product interms of human nutrition, e.g. omega-3fats, iodine, selenium, vitamins A and D.

cknowledgements

e author gratefully acknowledges SadasivamKaushik, Mali Boonyaratpalin, Santosh P. Lall,

yvind Lie, Torbjorn Asgard, Patrick Lavens,ewart Barlow, Albert G.J. Tacon, Freddy Ibd Chawalit Orachunwong for their generousntributions. The information generatedring the Nutrition Session of the Conferences been duly incorporated into theanuscript.

Akand, A.M., Soeb, M., Hasan, M.R. and Kibria,M.G. 1991b. Nutritional requirements of Indianmajor carp, Labeo rohita (Hamilton) - 1. Effectof dietary protein on growth, food conversionand body composition. Agricult. Int. 1: 35-43.

Alami-Durante, H. and Meyers, S. 1993.Concluding remarks: larval and crustaceannutrition. In S.J. Kaushik & P. Luquet, eds. Fishnutrition in practice, p. 638-641. Paris, INRA.

Alexis, M.N. 1997. Fish meal and oil replacersin Mediterranean marine fish diets. In A. Tacon& B. Basurco, eds. Feeding tomorrows fish, p.183-204. Proceedings of the workshop of theCIHEAM Network on Technology of Aquaculturein the Mediterranean (TECAM), jointly

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Alliot, E., Faber, A., Metailler, R. andPastowreaud, A. 1974. Nutritional requirementsof sea bass (Dicentrachus labrax) and study ofthe protein and lipid rate in the diet.Aquaculture, 10: 22-24.

Alvarado, J.L. 1997. Aquafeeds and theenvironment. In A. Tacon and B. Basurco, eds.Feeding tomorrows fish, p. 275-289.Proceedings of the workshop of the CIHEAMNetwork on Technology of Aquaculture in theMediterranean (TECAM), jointly organized byCIHEAM, FAO and IEO, Mazarron, Spain, 24-26June 1996, CIHEAM, Apodo, Spain.

Atack, T.H., Jauncey, K. and Matty, A.J. 1979.The utilisation of some single cell protein byfingerling mirror carp (Cyprinus carpio).Aquaculture, 18: 337-348.

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Nutrition and Feeding for Sustainable Aquaculture Development in the Third Millennium