Induced breeding of fishes:
Making fishes to spawn by artificial method is called induced breeding.
Indian major carps are induce to spawn by the injection pituitary extract is called Hypophysation. Therefore hypophysation is a techniques of induce breeding in Indian major carbs by pituitary gland extract.
Induce breeding without hormone treatment:-
Induce breeding in fishes is takes place by-
- Induce breeding without hormone Treatment.
- Induce breeding with pituitary gland extraction of fishes.
Mature breeding can be reproduce artificially by stimulate the events which they occurs during the rainy season which triggers off the making and spawning process.
Ponds of about 400 meter sq in size & fell with 25cm of water and stock with six mature female and 12 males. A few hours later the water level is raised up to level of 60cm spawning will occurs at night and following morning & the following morning the breeders can remove.
This technique is term artificial reproduction since offspring are produce.
Induce breeding with pituitary gland extraction from fish:-
In order to overcome the problem of sufficient fish seed supply, the induce breeding by hypophysation techniques has been devloped usually pituitary gland are used to induce the fish for spawning hormone secret by pituitary gland stimulate growth, development, maturity & ovulation of egg.
Principle of hypophysation:-
Environmental factors stimulate the hypothalamus of the brain, the hypothalamus secret a hormone called releasing hormone. The releasing hormone stimulate the pituitary gland to secret gonad Tropic hormone. The gonads in turn secret sex hormone the sex hormone produce the gamets, secondary sexual caracter, sexual behavior etc. this principle is applied on hypophysation.
Procedure of hypophysation:-
Hypophysation involve by the following steps:-
- Collection of pituitary gland
- Preparation of pituitary extract
- Solutions of breeders
- Injection of pituitary extract
Collection of pituitary gland:-
The 1st step in hypophysation is the collection of pituitary gland, the gland is collected from mature fishes.
The pituitary gland is located on the ventral side the brain. The head is dissected out to expose the brain. The brain is carefully detaching by the nerves. The deurameter covering of the gland is then removed using a fine needle & forceps. The expose gland is then picked up intract without causing any damage to it new gland preserved.
Preservation of pituitary gland:-
The collected gland must be preserved immediately because glycol or muco-protein containg them are degraded by the enzymatic action. The pituitary gland can be preserved by 3methods:-
- Absolute alcohol
But preservation of fish pituitary gland in absolute alcohol is prefered in India.
Preparation of pituitary extract:-
Preserve glands are wait for accurate determination of the dose to the given may be taken individually or in group. To get a more accurate weight, a gland should be weighed after 2minutes for its removal from alcohol. The pituitary extract should be prepared just be fore the injection.
The glands should macerated in a tissue homogeneous with a little distilled water. The homogeneous is diluted with distilled water. The preparation is centrifuge at about 1000rpm for 5minutes. The supernatural is the pituitary extract preserved in the glycol.
Selection of breeders:-
Mature male and female are selected & stock for hypophysation 2males & 1 females form 1 unit for hypophysation.
Injection of pituitary extract:-
The selected male and female are kept on a table on a cotton. The extract inject intramuscular at the base of pectoral fin or pelvic fins or chordal fins. About 0.5ml to 2 ml extract is given for breeders weight upto 10kg. The female given 2doses namely
- A preparatory dose
- A reserving dose
About 4hr interval given between 2doses. The male given 1dose.
Injection can be given at the day &night but generally after late afternoon or evening hours.
After the injection of pituitary extract the breeders are introduced into breeding happa. A breeding hapa is a rectangular is a mosquito net with enclosure. It is suspended in pond water with the help of 4 poles.
The running water similar to river conditions is maintain in the hapa. The breeders mate in hapa they breeds in 6hrs.
In 10hrs , the eggs are fertilize, the fertilize eggs are transferred into a hatching hapa, the hatching hapa consists of an inner hapa & outer hapa . The inner hapa smaller in size and fitted out side the happa.
The eggs are hatched into the inner hapa, the hatching wringing out though meshes of the inner hapa. Meshes of the inner hapa, the shell of dead eggs in the inner hapa are removed. The hatching are kept in outer hapa for 3days then they are transfer to the nursery ponds.
In recent years it is possible to breed the carps by hypophysation techniques in India almost thought the year except the month of January however the breeding sucess in the month of February &December is extremely limited.
Successful breeding of indian carps in October to December is confined to South India where winter season is mild & consequently water temp. Doesn’t fall very low & day is mach not reduce. Multiple breeding of Indian major carbs are different parts in India & Chinese carps to some extend also has been achieved.
Managements of nursery, rearing &stocking ponds:-
Nursery pond is used to rear hatching into fry for a period of 1month till the fry attain the size of 2cm to 2.5cm . It is a small pond the size should be 50ft to 60ft length / 30ft to 40ft breath /4ft to 5ft diameter with exist and with entrance control 3%of water area is altered for this pond.
The newly hatched fries are transported carefully from hatching hapa to nursery hapa. The nursery should be free from ace predatory animals and weeds chemical fertilizers are used before 10 to 20 days to devloped sufficient amount of zooplankton and phyto plankton. These plankton are the feed of the fries.
Mortality in nursery ponds:-
Mortality of fish fries are found in nursery ponds due to the following reason:-
- Change in quality of water while fries are transfers from hapa to nursery ponds.
- Overgrowth of plankton
- Lack of suitable & sufficient amount of food.
- Presence of predatory animals.
- Law oxygen concert. Of water.
Precautions for nursery ponds:-
Following precautions should be taken in the nursery ponds:-
- Nursery pond should be nearer to the hatchery.
- The temperature, oxygen conc. & food conc. Of water must be optimum.
- Running water is preferable.
- The pond should be free from predator.
- Over crowding should be avoided.
It is used to rear fry into fingerlings for a period of 2months until the fry attain the size of 4cm to 10cm . The size of the rearing ponds should be 25m/12m/1m.the depth of the water column should be 1.2 to 2mtr. The fingerlings can be transported from nursery ponds to rearing , rearing ponds for better wealth &development.
The rearing pond are longer & narrower ponds which provides long distance for swimming.
Precautions of rearing ponds:-
The following precautions:-
- The rearing ponds must be free from predators.
- The rearing ponds should be well maintain with optimum feed content quality of water, temperatures &oxygen.
- The food should have adequate nutritive food material as per the population of fingerling.
- After attaining about 20cm of length, the fingerlings should be transferred to stocking ponds.
- The use of antibiotics copper solt are necessary to free the fingerlings from any disease and parasites.
The stocking ponds are used for stocking the fingerlings before stocking of the fingerlings the stocking ponds should be clean from predatory animals, fishes and weeds.caw dunk Proper meaning must be done 10to 20 days before stocking for growth of phyto & zoo plankton, which become the main natural feed for fingerlings. Caw dunk at the rate of 20,000kg to 25,000kg per hector, per year should be given. The inorganic chemical fertilizers such as super phosphate ammonium nitrate, ammonium sulphate at the rate of 1,000 kg to 1,500 kg per hector per yr. Should be given.
The artificial diet made up of powder rice, paddy coconut, mustard, ground nut, etc are mostly used in the stocking pend these are easily digestive & economically.
Mostly the fingerlings are fed twice a day in the morning and evening. The feed matter should be adequately distributed the amount and type of fertilizers to be used must be considered by the facility of the soil and type of fishes. They may be harvested after attaining maximum length & weight.
Management of Hatchery of fishes:-
At present an integrated system is devloped where in breeding & hatching eggs and rearing of hatching for a few days are taken up as a part of a single system. The different types of hatchery are found . Which are describe below.
Modern Indian hatchery:-
This system consist of a unit of breeding tank of metal, cement or plastic pulls with cooling water or air conditioner to control the water temperatures & maintaining a slow continues flow of water. The water may be filtered by means of an in situ filter & to pump water to the storage tank.
The carp hatchery unit consist of source of water with an in situ filter. Pump, storage tank irrigation facility with an air compresser, vertical hatchery are made up of glass,galvanised iron sheets or poly there water supply system to the storage tank to the hatching jars or hatching storage tanks and water temperatures control mechanism.
The pilot hatchery and CIFRT cuttack and I used at malampuzha, Kerala, uder this category with some modifications.
The Chinese hatchery system is meant for incubating with high density of eggs.
7lakhs -12lakhs eggs per cubi meter & provided with running water. This consist of hatching with filtering serum, nozzles water & outlet value & fry collecting compartment.
This hatchery required large vol. Of water a combination of ground water & canal water or pond water are used gravitational force is normally used for the eggs to get into the hatching . Where in continuous circulation of water is maintain.