BREEDING OF TROUTSBREEDING OF TROUTS

INRODUCTION:INRODUCTION:--

Salmonid fishes viz. Salmonid fishes viz. pacific salmon (oncorhynchus sp.) Atlanticpacific salmon (oncorhynchus sp.) Atlantic salmonsalmon (Salmo sp.)(Salmo sp.)

Trouts are Trouts are grown in cold areasgrown in cold areas of world. Both pacific salmon & Atlantic of world. Both pacific salmon & Atlantic salmon are salmon are AnadromousAnadromous fishes and they fishes and they need saline environment forneed saline environment for growthgrowth..

But trouts can be grown in inland waters.But trouts can be grown in inland waters.

Contribution of salmonid to global aquaculture production of fishes is Contribution of salmonid to global aquaculture production of fishes is next to that of carps. Hundreds of hatcheries operate in several parts next to that of carps. Hundreds of hatcheries operate in several parts of cold areas of the world which are meant not only for providing of cold areas of the world which are meant not only for providing stocking materials for aqua farms but also for stock enhancement in stocking materials for aqua farms but also for stock enhancement in natural waters through ranching.natural waters through ranching.

Hatcheries of oncorhynchus and Salmo sp.Are engaged in the Hatcheries of oncorhynchus and Salmo sp.Are engaged in the production of production of smoltsmolt for farming and ranching.Trouts hatcheries are for farming and ranching.Trouts hatcheries are established in several cold regions of the world including India. established in several cold regions of the world including India. InIn India India trouts were introduced from other countriestrouts were introduced from other countries. . MahseeMahseer found in the r found in the cold streams and lakes are cold streams and lakes are endogenous fishesendogenous fishes in India. in India.

Trouts are grown in Trouts are grown in cold waterscold waters. there are 3 . there are 3 genera of cultivable trouts such asgenera of cultivable trouts such as

1)1)Rainbow troutsRainbow trouts ( (Salmo gairdneri or Salmo gairdneri or Oncorhynchus mykiss) Oncorhynchus mykiss)

2)2)Brown troutBrown trout ( (Salmo trutta farioSalmo trutta fario)) 3)3)Brook troutBrook trout ( (Salvelinus fontinalis). Salvelinus fontinalis).

In IndiaIn India trouts are trouts are exotic fishesexotic fishes, introduced , introduced into the cold waters mainly into the cold waters mainly of Jammuof Jammu Kashmir, Himachal Pradesh &peninsular India Kashmir, Himachal Pradesh &peninsular India (Nilgiri of T.N.and munnar high range of (Nilgiri of T.N.and munnar high range of Kerala). Kerala).

HISTORYHISTORY Eyed eggs of brown troutEyed eggs of brown trout were brought to India (Kashmir) from were brought to India (Kashmir) from

ScotlandScotland in year in year 19001900 by by F.J.MitchellF.J.Mitchell.. In 1912In 1912, Mitchell succeeded in , Mitchell succeeded in hatching rainbow trout eggshatching rainbow trout eggs

obtain from obtain from England.England.

After that After that Brook troutBrook trout introduced from introduced from CanadaCanada later. later.

Till early fifties trout culture done to met requirement of sport Till early fifties trout culture done to met requirement of sport fishery.fishery.

During During 1905-19061905-1906, a Brown trout hatchery was constructed at , a Brown trout hatchery was constructed at Harwan near Itinagar.Harwan near Itinagar.

In 1909, another hatchery at Katrain , Himachal Pradesh (Mahili In 1909, another hatchery at Katrain , Himachal Pradesh (Mahili hatchery)hatchery)

During 1909-1910at Avalanche in Nilgiris a trout hatchery was During 1909-1910at Avalanche in Nilgiris a trout hatchery was established. established.

REPRODUCTIVE BIOLOGYREPRODUCTIVE BIOLOGY

SEXUAL DIMORPHISMSEXUAL DIMORPHISMMALEMALE

Lower jaw is turned into a Lower jaw is turned into a kind of hooked beak kind of hooked beak shape.shape.

Genital papilla is absent Genital papilla is absent Brighter body coloration; Brighter body coloration;

as in rainbow trout males as in rainbow trout males have lateral iridescent have lateral iridescent bands &vivid stripes on bands &vivid stripes on lateral side which increase lateral side which increase in no. in no.

In brown trout belly turns In brown trout belly turns white stripes at outer white stripes at outer margin of anal fin.and in margin of anal fin.and in brook trout it is bright red brook trout it is bright red in colour. in colour.

On pressing abdomen milt On pressing abdomen milt oozes out. if milt is watery oozes out. if milt is watery it is of poor quality , if it is it is of poor quality , if it is creamy white it is of good creamy white it is of good quality.quality.

FEMALEFEMALE Hooked lower jaw is not Hooked lower jaw is not

present.present. Genital papilla is present Genital papilla is present

in fully ripe female.in fully ripe female. If belly of ripe female is If belly of ripe female is

pressed eggs shall blown pressed eggs shall blown out.out.

AGE AT FIRST SEXUAL MATURITYAGE AT FIRST SEXUAL MATURITY

IN MALES –attains at IN MALES –attains at end of 2 nd yearend of 2 nd year..

IN FEMALES –used for breeding from IN FEMALES –used for breeding from 3+ years onward upto 3+ years onward upto 6 th year.6 th year.

As age increasesAs age increases yield of yield of eggs also increaseseggs also increases but parts of but parts of their descendants may be sterile.their descendants may be sterile.

SPAWNING SEASON:SPAWNING SEASON: Rainbow trout –Rainbow trout –spring seasonspring season (January to may). (January to may).

Brown trout and Brook trout – (October to January) Brown trout and Brook trout – (October to January) fall/winter in USA/EUROPE.fall/winter in USA/EUROPE.

In India Brown and Brook trout breed - In India Brown and Brook trout breed - December to December to January.January.

Rainbow trout-during February to march except in Rainbow trout-during February to march except in avalanche, T.N. where it breeds from September to avalanche, T.N. where it breeds from September to February.February.

FECUNDITY:-FECUNDITY:- The spawning fecundity of trouts is The spawning fecundity of trouts is very lowvery low

i.e. i.e. 1500-2000 eggs per kg body weight. 1500-2000 eggs per kg body weight.

A trout hatchery should have the A trout hatchery should have the following units:following units:

1.1. Brood stock unit.Brood stock unit.

2.2. Egg taking unit.Egg taking unit.

3.3. Incubation unit.Incubation unit.

4.4. Larval rearingLarval rearing unit.unit.

BROODSTOCK UNIT:-BROODSTOCK UNIT:-

•Adequate care is taken to rear the brood fish so that healthy, Adequate care is taken to rear the brood fish so that healthy, viable eggs are obtained from it.viable eggs are obtained from it.

•The brood fish can be collected from natural, open waters or The brood fish can be collected from natural, open waters or they can be raised in ponds. They are collected from they can be raised in ponds. They are collected from open wateropen water while they are while they are swimming upstream prior to spawningswimming upstream prior to spawning..

•Pond raised breeders are reared in raceways of circular, Pond raised breeders are reared in raceways of circular, rectangular or hexagonal shape or in grow out ponds.rectangular or hexagonal shape or in grow out ponds.

For raising the brood stock, a For raising the brood stock, a trout farm should have the trout farm should have the following:following:

Optimum climatic condition.Optimum climatic condition.

A A source of adequate water supplysource of adequate water supply for maintaining the required water for maintaining the required water flow in the ponds.flow in the ponds.

Good water of qualityGood water of quality..

OPTIMUM CLIMATIC CONDITIONOPTIMUM CLIMATIC CONDITION::

TEMPERATURETEMPERATURE:: As are cold water fishes, tolerable limits of As are cold water fishes, tolerable limits of temperature for adults is temperature for adults is 12ºC to 14ºC12ºC to 14ºC for for brook troutbrook trout , ,10ºC to 10ºC to 20ºC for rainbow trout and20ºC for rainbow trout and brown troutbrown trout. So there has to be . So there has to be moderate and uniform temperature.moderate and uniform temperature.

RAINFALLRAINFALL:: Rainfall has to be Rainfall has to be moderate moderate since heavy rainfall since heavy rainfall areas are deficient in mineral contents.areas are deficient in mineral contents.

GRADIENTS:GRADIENTS: Mountainous terrain with steep gradient is also deficient in Mountainous terrain with steep gradient is also deficient in

mineral contents.mineral contents.

Adequate lime stone and other minerals deposits in the areasAdequate lime stone and other minerals deposits in the areas are desirableare desirable to ensure mineral rich water as water containing to ensure mineral rich water as water containing calcium is richer in natural food and is the most productive calcium is richer in natural food and is the most productive water from granite sources though pure is not rich in natural water from granite sources though pure is not rich in natural food.food.

SOURCE OFWATERSOURCE OFWATER: Water from : Water from rheocrene andrheocrene and limnocrene springlimnocrene spring is considered as ideal for rearing of is considered as ideal for rearing of trout.trout.

There are 3 types of spring:There are 3 types of spring:

Rheocrene springRheocrene spring: In this category,on emerging the water : In this category,on emerging the water runs down towards the valley through a slope.runs down towards the valley through a slope.

Limnocrene springLimnocrene spring: The spring is located in a depression as : The spring is located in a depression as a result the spring water fills the natural depression.a result the spring water fills the natural depression.

HelocreneHelocrene springspring: The water seeps through a thick layer of : The water seeps through a thick layer of earth and transforms the ground into a marsh. The water earth and transforms the ground into a marsh. The water will be rich in humic acid and organic matter. This is not will be rich in humic acid and organic matter. This is not suitable for trout farm.suitable for trout farm.

While While spring waterspring water shall be ideal shall be ideal for hatcheryfor hatchery, , streamstream

waterwater can be used can be used for grow out pondsfor grow out ponds. .

WATER QUALITYWATER QUALITY: Water should be : Water should be pure, free from pollutants, pure, free from pollutants, transparent & free from dirt and suspended particles.transparent & free from dirt and suspended particles.

TURBIDITY:TURBIDITY: Turbidity @100 ppm and above chokes the gills of Turbidity @100 ppm and above chokes the gills of

fry and fingerlings. Even 25 ppm hampers normal development fry and fingerlings. Even 25 ppm hampers normal development of trout egg, delays hatching &causes deformities in the of trout egg, delays hatching &causes deformities in the hatchlings. hatchlings.

DISSOLVE OXYGENDISSOLVE OXYGEN: The DO level has to be : The DO level has to be 9 ppm9 ppm that is that is almost double that is required for cyprinids. If it is almost double that is required for cyprinids. If it is below 5 ppmbelow 5 ppm fish develop respiratory difficultiesfish develop respiratory difficulties. Normally, in spring water it . Normally, in spring water it may be may be 8.5-9.4 ppm8.5-9.4 ppm where as in where as in streamstream it may be it may be 7.4-10.2ppm 7.4-10.2ppm..

pH pH : If the pH is : If the pH is about or above 9 , it causes mortality amongabout or above 9 , it causes mortality among

eggs and alevinseggs and alevins. Usually, . Usually, spring water of Himalaya has pH ofspring water of Himalaya has pH of 7.9-8.4.7.9-8.4.

FEEDINGFEEDING: Feeding the brood stock with adequate feed of good : Feeding the brood stock with adequate feed of good

quality is of prime importance in raising good quality brood quality is of prime importance in raising good quality brood stock. As it will be impossible to obtain and feed only natural stock. As it will be impossible to obtain and feed only natural food to fish, good quality artificial food is usually recommended. food to fish, good quality artificial food is usually recommended. Feeding the brood fish Feeding the brood fish @ 1-2% of body weight with 1:1 mixture @ 1-2% of body weight with 1:1 mixture of meet balls of snow trout and mirror carp has been found of meet balls of snow trout and mirror carp has been found effective effective

SEX RATIO FOR THE BROOD STOCK:SEX RATIO FOR THE BROOD STOCK:

The The number of malesnumber of males can be can be half the no. orhalf the no. or even one third of the no. of femaleseven one third of the no. of females..

This is because of the fact that This is because of the fact that males gives miltmales gives milt several timesseveral times i.e. 3 to 8 times in a season i.e. 3 to 8 times in a season provided that successive spawnings are provided that successive spawnings are separated by 2 weeks.separated by 2 weeks.

Usually Usually milt from 1 male is sufficiently to milt from 1 male is sufficiently to fertilize eggs from 2 females.fertilize eggs from 2 females.

Males are usually segregated from female at Males are usually segregated from female at least 3 month during the breeding season as least 3 month during the breeding season as they fight between each other if left with they fight between each other if left with females. females.

EGG TAKING AND MILT COLLECTIONEGG TAKING AND MILT COLLECTION::

WET METHOD Vs DRY MEHODWET METHOD Vs DRY MEHOD:: The eggs from female and milt from male collected The eggs from female and milt from male collected by by

strippingstripping i.e. by applying gentle pressure on both sides i.e. by applying gentle pressure on both sides of the belly moving the fingers front to back.of the belly moving the fingers front to back.

In the In the wet methodwet method, eggs are collected in a pan , eggs are collected in a pan

containing water & then the milt is added to it for containing water & then the milt is added to it for fertilizing eggs.fertilizing eggs.

In the In the dry methoddry method, the eggs are collected into a dry , the eggs are collected into a dry receptacle into which the milt is added. After mixing receptacle into which the milt is added. After mixing milt with eggs i.e. after fertilization is over, the mixture milt with eggs i.e. after fertilization is over, the mixture is poured into a pan half filled with water.is poured into a pan half filled with water.

Dry method is preferable for the following reasons:Dry method is preferable for the following reasons:

1) if the milt is not mixd in water spermatozoa of trout 1) if the milt is not mixd in water spermatozoa of trout remain vaiable for longer duration ( even upto 2-10 remain vaiable for longer duration ( even upto 2-10 days at 4ºC to 8ºC).days at 4ºC to 8ºC).

If the milt is mixd in water it is viable only for If the milt is mixd in water it is viable only for maximum 90 seconds but greater part of motility maximum 90 seconds but greater part of motility caeses after 30 sec. caeses after 30 sec.

If the eggs come into contact with water, eggs absorb If the eggs come into contact with water, eggs absorb water and swell as a result the micropyle- the route by water and swell as a result the micropyle- the route by which the sperms enters into the egg – closes. As a which the sperms enters into the egg – closes. As a result of this sperm penetration and subsequent result of this sperm penetration and subsequent fertilization become impossible.fertilization become impossible.

Egg Taking ProcedureEgg Taking Procedure::

There are methods of egg taking of trouts such asThere are methods of egg taking of trouts such as 1)Hand stripping without incision1)Hand stripping without incision (one man method and two man method) (one man method and two man method)

2) Hand stripping after incision2) Hand stripping after incision 3) Australian method 3) Australian method

4) Swedish method.4) Swedish method.

HAND STRIPPING WITHOUT INCISION:HAND STRIPPING WITHOUT INCISION: ONE MAN METHOD:ONE MAN METHOD:

The female fish in the ripe condition is The female fish in the ripe condition is wiped gentlywiped gently so that water from so that water from the body will not drop into the container for collecting eggs.the body will not drop into the container for collecting eggs.

After wiping the female is held with the After wiping the female is held with the ventral side directed downventral side directed down above the pan by one hand of the operator whereas by the other hand above the pan by one hand of the operator whereas by the other hand he exerts a pressure on the belly which causes the egg to flow through he exerts a pressure on the belly which causes the egg to flow through the vent which is taken in to the spawning pan. the vent which is taken in to the spawning pan.

TWO MAN METHOD:TWO MAN METHOD:

In two man method one person holds the fish and other does the In two man method one person holds the fish and other does the stripping operation.stripping operation.

The fish is held in a The fish is held in a steeply inclined positionsteeply inclined position with the head held with the head held up , up , back towards the operatorback towards the operator and underside over the pan. and underside over the pan. Pressing with the thumb and index finger on the belly, hand is Pressing with the thumb and index finger on the belly, hand is moved down on the abdomen and as it descends over the lower moved down on the abdomen and as it descends over the lower end of the body eggs start flowing through the genital opening. end of the body eggs start flowing through the genital opening. The process can be repeated several times so that the female is The process can be repeated several times so that the female is completely emptied the eggs.completely emptied the eggs.

Care is taken not to exert excess pressure on the abdomen so Care is taken not to exert excess pressure on the abdomen so that internal haemorrhages do not occur. If any vein is ruptured that internal haemorrhages do not occur. If any vein is ruptured it causes the flow of blood and the same may contaminate the it causes the flow of blood and the same may contaminate the eggs and harm the mother fish.eggs and harm the mother fish.

Milt collection is also done in a similar way. The body of the male Milt collection is also done in a similar way. The body of the male is wiped so that water does not drip from the body into the is wiped so that water does not drip from the body into the container. Under side is then turned downwards and sides are container. Under side is then turned downwards and sides are pressed. Milt flows through the urino genital aperture ands the pressed. Milt flows through the urino genital aperture ands the same is taken into a sterile tube.same is taken into a sterile tube.

HAND STRIPPING AFTER INCISION:HAND STRIPPING AFTER INCISION:

Incision is made in the vent regionIncision is made in the vent region to facilitate easy to facilitate easy flow of sexual products.flow of sexual products.

It is practiced in species of salmon which die after It is practiced in species of salmon which die after spawning e.g. spawning e.g. oncorhynchus.oncorhynchus.

milt collection is done in a similar way. The male is milt collection is done in a similar way. The male is wiped so that water does not drip from the container.wiped so that water does not drip from the container.

Underside is then turned downwards and Underside is then turned downwards and sides aresides are pressedpressed. Milt flows out through the . Milt flows out through the urinogenital urinogenital apertureaperture and the same is taken into a sterilized tube. and the same is taken into a sterilized tube.

AUSTALIAN METHODAUSTALIAN METHOD::

In the In the year 1950year 1950, an Australian farmer named , an Australian farmer named WortonWorton introduced introduced this method. Hence it is called this method. Hence it is called Worton’s methodWorton’s method..

A hypodermic injection needle is attached to a bicycle pump A hypodermic injection needle is attached to a bicycle pump through a rubber tube. The needle is inserted into the body cavity through a rubber tube. The needle is inserted into the body cavity near the pelvic fin.near the pelvic fin.

The needle is held firmly in position and the air is gently pumped The needle is held firmly in position and the air is gently pumped into the body cavity through the needle which expels the egg into the body cavity through the needle which expels the egg through the vent. After all the eggs exude out, the air pumped through the vent. After all the eggs exude out, the air pumped inside the abdominal cavity of the fish is carefully siphoned out by inside the abdominal cavity of the fish is carefully siphoned out by the mouth of the operator and the fish is returned to the holding the mouth of the operator and the fish is returned to the holding tank.tank.

In case of male, the needle is inserted into vasdeferens and the In case of male, the needle is inserted into vasdeferens and the milt is sucked out and taken to a test tube.milt is sucked out and taken to a test tube.

In some of the trout farms of USA a modified method In some of the trout farms of USA a modified method is used. In this method, instead of cycle pump, is used. In this method, instead of cycle pump, air air compressorcompressor (1.6 H.P.motor)is used which is connected (1.6 H.P.motor)is used which is connected to a rubber tube connected to the outer barrel of a to a rubber tube connected to the outer barrel of a hypodermic syringe which is inserted into the body hypodermic syringe which is inserted into the body cavity near pelvic girdle.cavity near pelvic girdle.

When the compressor is turned on, compressed air When the compressor is turned on, compressed air enters the abdominal cavity at a pressure of enters the abdominal cavity at a pressure of 0.40.4 kg/cm²kg/cm²..

Then the fish in inverted and gently shaken to release Then the fish in inverted and gently shaken to release the eggs. After the eggs flows out, the same pump is the eggs. After the eggs flows out, the same pump is used to suck out the air from inside also.used to suck out the air from inside also.

In this, the entire process is finished within 15 In this, the entire process is finished within 15 seconds. The eggs are allowed to fall on a net sieve seconds. The eggs are allowed to fall on a net sieve through which waste material pass out, clean eggs through which waste material pass out, clean eggs without faecal matter is transferred to dry container. without faecal matter is transferred to dry container.

THE SWEDISH METHOD: THE SWEDISH METHOD: Female is placed in a double walled rubber sac Female is placed in a double walled rubber sac

having a holder to hold the fish closely.having a holder to hold the fish closely.

While keeping the fish, the tail part up to the vent is While keeping the fish, the tail part up to the vent is left protruding which is held by the operator.left protruding which is held by the operator.

The space between the two walls is connected to a The space between the two walls is connected to a water tap. As the tap is opened, the water enters water tap. As the tap is opened, the water enters into the sac presses against the whole fish.The fish into the sac presses against the whole fish.The fish readily releases the eggs which are taken in to the readily releases the eggs which are taken in to the container.container.

Milt is also taken in a similar way Milt is also taken in a similar way

FERTILISATION:-FERTILISATION:- One cubic centimeterOne cubic centimeter of trout milt may have of trout milt may have 10,000 10,000

millionmillion spermatozoaspermatozoa. Hence only a few drops are . Hence only a few drops are required for a large quantity of eggs.required for a large quantity of eggs.

Usually Usually milt from 2 malesmilt from 2 males is used to is used to fertilize eggs from fertilize eggs from 2-4 females.2-4 females.

The eggs and milt are mixed well with the aid of a The eggs and milt are mixed well with the aid of a feather and this is poured into a pan having water.feather and this is poured into a pan having water.

Then they again mixed well 3-4 times with fethery Then they again mixed well 3-4 times with fethery carefully.Fertilisation takes place immedietly.carefully.Fertilisation takes place immedietly.

Only one sperm is allowed to enter through the Only one sperm is allowed to enter through the micropyle and form the zygote nucleus. This is set micropyle and form the zygote nucleus. This is set aside for an hour for the eggs to harden. aside for an hour for the eggs to harden. Fertilized Fertilized eggs have a greenish tinge. eggs have a greenish tinge.

INCUBATION OF FERTILIZED EGGS INCUBATION OF FERTILIZED EGGS After the trout eggs are water After the trout eggs are water

hardened and counted, they are hardened and counted, they are transferred to a hatchery for transferred to a hatchery for incubation.incubation.

Incubation devices for trout eggs:-Incubation devices for trout eggs:-1.1. Flat troughs and trays,Flat troughs and trays,2.2. Vertical flow incubators,Vertical flow incubators,3.3. Vibrate box Vibrate box 4.4. Jar container.Jar container.

Flat trough and trays:Flat trough and trays: The classical incubation device of trout eggs The classical incubation device of trout eggs consist of troughsconsist of troughs in in

which one or many meshed trays are kept.which one or many meshed trays are kept.

The eggs are placed in the The eggs are placed in the meshed traysmeshed trays. The trays are made of . The trays are made of perforated stainless steel/ aluminium /zinc/plastic.perforated stainless steel/ aluminium /zinc/plastic.

The mesh size is The mesh size is 1.5 to 2.5 mm1.5 to 2.5 mm in diameter. Sometimes, in diameter. Sometimes, the the bottom of the tray by a space of 2bottom of the tray by a space of 2 mm.mm.

The size of the tray should be in such a way that it will fit into the The size of the tray should be in such a way that it will fit into the through easily. Tray may through easily. Tray may rest on ridgesrest on ridges fixed to the inside wall of fixed to the inside wall of the though orb tray may stand on legs resting on the bottom of the the though orb tray may stand on legs resting on the bottom of the through.through.

The space between side of through and tray must be as narrow as The space between side of through and tray must be as narrow as possible so that water flow shall be from bottom to top across the possible so that water flow shall be from bottom to top across the tray. The space can be filled with foam rubber to ensure this. tray. The space can be filled with foam rubber to ensure this. A tray A tray of 50X50 cm holds a layer ofof 50X50 cm holds a layer of 10000 eggs10000 eggs. The trays are provided . The trays are provided with wooden /metal/eternite lids as hatching always takes place in with wooden /metal/eternite lids as hatching always takes place in dark. The through are either short (California type) or long shaped. dark. The through are either short (California type) or long shaped.

CALIFORNIA TYPE:CALIFORNIA TYPE: These are short through made ofThese are short through made of zinc zinc

sheet or wood plasticsheet or wood plastic of size of size 0.5X0.2X0.15 0.5X0.2X0.15 (20x8X6 inch)or (20x8X6 inch)or 1X5X0.25 m1X5X0.25 m (40X20X10)inch.(40X20X10)inch.

The former can hold one tray whereas the The former can hold one tray whereas the

latter can hold 2 trays.latter can hold 2 trays.

These These troughs can be arranged in tierstroughs can be arranged in tiers so so that water can flow from the upper tier to that water can flow from the upper tier to the next tier. the next tier.

LONG TROUGH:LONG TROUGH: A long shaped through may be A long shaped through may be 2 to 3 m. in2 to 3 m. in

length, 0.5-0.8 m. in width 0.2-0.35 in depth.length, 0.5-0.8 m. in width 0.2-0.35 in depth.

The trough may be made of The trough may be made of concrete / cemented concrete / cemented bricks / zinc sheet/wood or wood covered with bricks / zinc sheet/wood or wood covered with zinc sheet / aluminium or steel.zinc sheet / aluminium or steel.

The The inside of the trough is usually painted with inside of the trough is usually painted with dark coloured water proof paintsdark coloured water proof paints so that so that eggs willeggs will be protected from bright lightbe protected from bright light. This type of . This type of troughs is useful for both hatching and rearing of troughs is useful for both hatching and rearing of fry upto 3 months fry upto 3 months

VERTICAL INCUBATORS:VERTICAL INCUBATORS: When incubation is done in flat troughs with trays inside, When incubation is done in flat troughs with trays inside,

whether troughs are arranged in tiers or placed parallel to whether troughs are arranged in tiers or placed parallel to each other, incubation unit shall occupy a large part of the each other, incubation unit shall occupy a large part of the building.building.

Hence in order to overcome this difficulty, vertical Hence in order to overcome this difficulty, vertical incubation models have been incubation models have been developed in countries like developed in countries like USA and Sweden.USA and Sweden.

The most popular of this consist of The most popular of this consist of one or twoone or two superimposed shelves, each one holding superimposed shelves, each one holding 8 incubation trays8 incubation trays. . Each tray is made up of an external basket which can hold Each tray is made up of an external basket which can hold water.water.

The eggs containing tray is kept inside this basket. This tray The eggs containing tray is kept inside this basket. This tray is covered with mesh lid. The whole device is the water tray is covered with mesh lid. The whole device is the water tray is is 53X62X9 cm53X62X9 cm., eggs container tray is ., eggs container tray is 40 X 35 X5 cm40 X 35 X5 cm the the water that into the top most water after filling in the same water that into the top most water after filling in the same shall flow into the tray below ultimately passes out from the shall flow into the tray below ultimately passes out from the lower most tray. lower most tray.

A modified vertical flow incubator has being used in the Laribal A modified vertical flow incubator has being used in the Laribal hatchery in Kashmir in india.hatchery in Kashmir in india.

It consist of a drum having a water inlet at the bottom and It consist of a drum having a water inlet at the bottom and outlet at the top.outlet at the top.

Just above the water intake point, a filter made of metallic wire Just above the water intake point, a filter made of metallic wire holding pebbles is placed.holding pebbles is placed.

Another circular tray containing eggs is hung with nylon Another circular tray containing eggs is hung with nylon twine , below the outlet point.twine , below the outlet point.

As the water is let into the drum from below, it passes through As the water is let into the drum from below, it passes through

the filter which helps in removing suspended particles found in the filter which helps in removing suspended particles found in the water. the water.

As the filtered water swells up the drum, it bathes the eggs As the filtered water swells up the drum, it bathes the eggs kept in the egg tray and then it passes out through the outlet. kept in the egg tray and then it passes out through the outlet. Thus the eggs are bathed in filtered, clean, clear water Thus the eggs are bathed in filtered, clean, clear water continuously.continuously.

VIBERT SYSTEM:VIBERT SYSTEM: In this system eggs are kept in a cage called In this system eggs are kept in a cage called vibert boxvibert box

designed by vibert (1975designed by vibert (1975). Each box of the size ). Each box of the size 70 X 63 X70 X 63 X 94 mm94 mm and and weight about 45 gmweight about 45 gm and is and is made of rigidmade of rigid transparent plastic materialtransparent plastic material..

The holes are drilled in the walls diameter of which is The holes are drilled in the walls diameter of which is smaller than the egg size but at the same time large smaller than the egg size but at the same time large enough for the fry to swim out and it holds about 1000 enough for the fry to swim out and it holds about 1000 trouts or 800 Salmon eggs.trouts or 800 Salmon eggs.

The box is immersed in river bed where there is swift water The box is immersed in river bed where there is swift water current and the clear water. Bottom of the stream should current and the clear water. Bottom of the stream should have pebbles of the size of hen’s egg. A hole dipper than have pebbles of the size of hen’s egg. A hole dipper than the box size is dug in the stream bed into which the vibert the box size is dug in the stream bed into which the vibert box with eggs is placed.box with eggs is placed.

Around the box larger stone are kept to create empty space Around the box larger stone are kept to create empty space against the side the box. The hole is then filled with smaller against the side the box. The hole is then filled with smaller gravel prevents predators from reaching the spot and also gravel prevents predators from reaching the spot and also ensure complete darkness. Larger stone will have space in ensure complete darkness. Larger stone will have space in between which allows the alvin to escape into the river.between which allows the alvin to escape into the river.

THE JAR SYSTEM:THE JAR SYSTEM:

Another method of incubation of trout eggs is doing so in jars. Another method of incubation of trout eggs is doing so in jars. This involves keeping eggs in jars which is accomplished by This involves keeping eggs in jars which is accomplished by providing providing inlet about ½” above their base.inlet about ½” above their base.

Then a quarter of routing gravel in is poured on the top of 1/8 Then a quarter of routing gravel in is poured on the top of 1/8 galvanized screen with water inlet situated below it. These galvanized screen with water inlet situated below it. These prevents gravel from blocking the inlet. Some sort of wire prevents gravel from blocking the inlet. Some sort of wire netting is placed after Fertilisation.netting is placed after Fertilisation.

Water coming from shallowest part of jar passes through gravel Water coming from shallowest part of jar passes through gravel & is evenly dispersed through eggs.& is evenly dispersed through eggs.

No special washing of eggs is necessary in this system this No special washing of eggs is necessary in this system this method of incubation has many advantages. method of incubation has many advantages. It permits vertical It permits vertical use of hatchery building, saves space and there by economicsuse of hatchery building, saves space and there by economics in construction costin construction cost. The actual hatching units are cheap to . The actual hatching units are cheap to construct. construct.

DEVELOPMENT OF EGGS:The fertilized egg undergoes development till the embryo is fully ready to hatch out the eggs.

The four stages of importance from the point of view of a pisiculturist are •Green egg•eyed eggs•alvin or sac fry•Swim up fry.

The newly fertilized egg is called green egg because of the greenish tinge of colour of the egg.

In course of development when the embryo develops eye which is visible through the egg envelope it is called quiescent at the bottom of the incubation apparatus. It may take 15-18 days for the yolk sac to be absorbed in rainbow trout. When 2/3 of the yolk sac is absorbed, larva starts moving towards water surface and this stage is called swim up fry. At this stage it starts active feeding.

CARE OF EGGS DURING INCUBATION:

CONTINOUS AND UNIFORM WATER FLOW: The incubation unit has to be supplied with a continuous and uniform flow of water so that eggs are bathed in fresh water always.

The rate of water flow can be 0.2 to 0.3 lit./min/1000 eggs.

This ensures not only the required dissolved oxygen level in the rearing medium but also the removal of metabolic waste from it.

Water supply for the trout hatchery shall be from rheocrene or limnocrene spring.

WATER TEMPERATUREWATER TEMPERATURE Temperature of water Temperature of water should not be below should not be below

1.5ºC and above 14ºC. 1.5ºC and above 14ºC.

TheTheincubationperiodincubationperiod(period (period fromfertilization to the hatching)and fromfertilization to the hatching)and period for transformation from alevins to period for transformation from alevins to swim up fry are swim up fry are 72 to 90 days and 32 to 40 72 to 90 days and 32 to 40 days respc. days respc.

The incubation period also depends on the The incubation period also depends on the quality of the egg as eggs taken from quality of the egg as eggs taken from different parents may have different different parents may have different periods of incubations at a given temp. periods of incubations at a given temp.

QUALITY OF WATER:QUALITY OF WATER: Water should be Water should be clear,clear, free of silt particlesfree of silt particles as silt as silt

particles may settle on eggs and prevent the particles may settle on eggs and prevent the exchange of gases. There will be also higher risk of exchange of gases. There will be also higher risk of infection.infection.

It is done by lifting and submerging the tray in water It is done by lifting and submerging the tray in water simultaneously spraying them with water from a simultaneously spraying them with water from a sprinkler.sprinkler.

OXYGEN CONTENT OF WATEROXYGEN CONTENT OF WATER:: It should be from It should be from 6-8 ppm.6-8 ppm.

PROTECTION FROM SUNLIGHTPROTECTION FROM SUNLIGHT:: Direct sunlight and electric light are harmful to Direct sunlight and electric light are harmful to

developing embryos. So the developing embryos. So the eggs must be kept in eggs must be kept in darkness. darkness.

REMOVAL OF DEAD EGGSREMOVAL OF DEAD EGGS:: common infection is of common infection is of saprolegniasaprolegnia..

The disinfection is done at a time when The disinfection is done at a time when the the eggs are least sensitive to external eggs are least sensitive to external stress.stress.

This safe period is This safe period is either one day after either one day after fertilization or during the eyed egg fertilization or during the eyed egg stage.stage.

MAINTENANCE OF GENERAL MAINTENANCE OF GENERAL HYGIENE:HYGIENE:

Both Both prophylactic as well as therapeuticprophylactic as well as therapeutic measures are to be taken measures are to be taken to avoid disease out break in incubation units. to avoid disease out break in incubation units.

DisinfectionDisinfection used to used to prevent fungal infectionprevent fungal infection are are malachite green, malachite green, acriflavin, gentian violet and potassium permanganateacriflavin, gentian violet and potassium permanganate. .

Prophylactic measuresProphylactic measures to prevent fungal attack is by to prevent fungal attack is by treating the treating the egg for about 30 min.egg for about 30 min. in a mixture of malachite green with water in a mixture of malachite green with water @5 mg malachite green per liter of water@5 mg malachite green per liter of water. After this it is flushed . After this it is flushed and fresh water is pumped in taking care not to disturb the eggs. and fresh water is pumped in taking care not to disturb the eggs.

Before adding malachite green solution, utmost care is takenBefore adding malachite green solution, utmost care is taken to to ensure thatensure that every crystal is completely dissolvedevery crystal is completely dissolved. The solution . The solution must be uniformly spread in the trough very carefully without must be uniformly spread in the trough very carefully without disturbing the eggs. If it is not uniformly spread, there may be disturbing the eggs. If it is not uniformly spread, there may be hyper concentration of the dye in localized areas in the trough hyper concentration of the dye in localized areas in the trough which may prove toxic to the eggs. This treatment shall continue which may prove toxic to the eggs. This treatment shall continue till the alevins emerge. till the alevins emerge.