Carp, eggs, after fertilisation swell to the size of a pea and are non-adhesive and demersal. The specific gravity of eggs is slightly higher than that of water. The eggs settle to the bottom in quiet water but, with slight disturbance, come up to the surface of water. The incubation period is about 15-18 hours at temperature 270-310C. The period of incubation however, varies depending on the water temperature.
Removal of Eggs For Hatching
The fertilized eggs are transferred from the breeding happa as soon as they get properly water hardened. Usually the eggs are removed about 8-10 hours after fertilization, when the embryo just starts twitching movements. The breeders are removed carefully and then the eggs are collected in enamel buckets. Quantitative and qualitative estimate of eggs are then made from representative samples. The eggs are then distributed to a series of hatching happas for hatching.
Hatchling of Carp Eggs
The hatching are fixed in the marginal waters of ponds and tied to bamboo poles. A hatching happa actually consists of two separate happas, one fitted inside the other. The outer happa is usually made of thick-meshed cloth, where as, the inner one is made of round-meshed mosquito net cloth. Extreme care is taken to properly stretch the bottom of the inner happa in a perfectly horizontal position at a level of about 0.3 metre under the surface of water. For perfect stretching floating inner happa fixed on a cage or wooden frame is also used. The eggs are uniformly distributed all over the inner hatching happa. In each hatching happa (1.8m x 0.9m. x 0.9m.) about 75,000 to 1,00,000 eggs are kept for hatching.
The hatchlings escape into the outer happa through the meshes of inner one. Bad eggs and egg cases remain in the inner happa which is removed when all the eggs have hatched out. The hatchling are left in the outer happa for 48 to 60 hours after hatching. During the period, the yolk is almost absorbed, mouth is formed and the post larvae starts feeding. At this stage, the spawn is collected carefully from the outer hatching happa, quantity estimated and stocked into the nursery ponds for rearing.
Design and Operation of Circular Fish Seed Hatchery
The Chinese spawning and hatching system is based on continuous flow of water to breed carps and hatch the eggs. The system is now considered to be highly suitable for the production of quality fish seed in India.
This system is designed for fish breeding and incubation. It has got four main components, namely overhead water storage tank, spawning pool, hatching pool and spawn receiving pond. The water required for the system is regulated through pipe supply from an overhead tank. The duration of one operation for hatching is 4 days. It can be repeated after 4 days interval.A, 4 metre internal dia, spawning pool with 1.5 metre dia. Hatching pools can give about 20 lakh of spawn per charge. 95% spawn hatching is possible in this system.
- Overhead Water Storage Tank
The water supply system for hatchery is regulated through pipes from overhead tank. The floor of the tank should be 2.6 m. above ground level. The inside dimension can be 3.5m. x 2.0m. x 2.0m. having a capacity of 15000 litres. Water supply to overhead tank is to be arranged by pumping water from an open well or deep tube-well.
Spawning Pool
Spawning pool is a circular brick masonary concrete pond having inside dimension of 4 m. dia. The inside depth at the periphery is 1.2 m, which slopes down to the centre at 1.5 m. Water supply to this pond is from overhead water tank by means of 5 cm.dia.pipe. The water supply line is laid along the outside of the wall and the inlet to the pond is provided at 14 to 16 places equally spaced and fixed at an angle of 450to the radius of the tank using 20 mm.dia.pipe with nozzle mouth, all in one direction. They are fixed to the vertical wall and the nozzle mouth is flushed with cement plaster face, near the bottom along the periphery of the pond.
In the centre, an out let pipe of 5 cm.dia.is fitted through which, on opening the valve, fertilised eggs along with water are transferred into the hatching pool.
Hatching Pools
There may be two or more hatching pools depending on the frequency of operation of spawning pool. Each hatching pool with 1.5m. internal dia.consists of 2 chambers. The outer dimension is 2m. having outer masonary or concrete wall. Another circular wall with fixed M.S.screen is provided at 0.5 m. clear distance from the outer wall. The inner chamber is provided with 5 cm.dia.vertical outlet with holes at different heights for taking excess water. The spawn along with water flows from these pools to spawn receiving pond.
From overhead tank, by 5 cm.dia.pipe line reduced to 2.5 cm.dia.pipe line and them to 1.2 cm.dia.pipe line. Eight nos. of outlets are fitted in the floor having duck mouth opening fixed in one direction at an angle 450 towards inner wall.
Water supply pipe are fitted from the spawning pool by 7.5 cm.pipe line and then bifurcated into two or three depending on the number of hatching pool, which are further connected to duck mouths in the floor of hatching pools.
There is an outlet of 5 cm.dia.pipe through which spawn pass into receiving pond. This opening is also used for complete dewatering of the hatching pool. Water in the hatching pool should flow at the rate of 0.2 to 0.3 m.per second.
The spawn receiving pond may be an earthen pond, of the size of nursery pond and should be located at lower elevation than the hatching pool so as the drain out the spawn with water from it by gravity. From each of the hatching pool 5 cm.dia.pipes are provided for transfer of spawn into the receiving pond, where cloth happa is fixed with the help of bamboo poles into which spawn from each of the hatching pool is collected, measured and transferred into well prepared nursery tanks for rearing.
Operation Of The Hatchery
Brood fishes are put into the spawning pool for about 4 to 8 hours for conditioning. Between 4 to 6 P.M. first injection is given to the females. At a time 20 kg. of females and 25 kg.of males are put in. After six hours of first injection, a second dose of injection if given to the females and one dose to the males. After 4 hours of the second injection, the waterjets are started so as to get the circular water motion. 6 to 8 hours after the second injection spawning takes place. The eggs are collected from the bottom and transferred into spawning pools through pipe lines by opening the valve. Arrangement are made to flow water in the hatching pools through duck mouths in a circular motion and continues for 4 days time till the spawn attain 6 mm.size, from where they are removed into spawn receiving pond for stocking in nursery ponds.
If oxygenation is less, aeration can be given through compressor in the hatching pool at the rate of 6 kg./cm2 run by 1 H.P.motor. For aeration, water showers, water jets etc.can also be provided depending upon the requirements.
The advantage of seed production through eco-hatcheries attracted the attention of all the States and made them adopt this technique in public as well as private sector, though slowly but steadily. Today, in almost all the major States, such type of hatcheries can be seen either in Government or in the private sector. At present, there are about 400 such hatcheries in the country including 46 commercial fish seed hatcheries in different parts of the country, of which 18 were sanctioned under the World Bank aided Inland fisheries Project in the States of Bihar, Madhya Pradesh, Orissa, Uttar Pradesh and West Bengal and the remaining 28, under the National Fish Seed Production Programme in other States. These 46 modern fish seed hatcheries have the capacity to produce about 1046 million fry per annum.
The revolution in fish seed production could be made possible by the establishment of a large number of commercial eco-hatcheries both in the Government and private sectors in West Bengal. This initiative in West Bengal has led the State to become the leader not only in carp seed production but also in aquacultural production.
Ag.
Technologies
(Fisheries)
