Chinese spawning and hatching systems are based on continuous flow of water by gravity to breed carps and hatch the eggs.The cost of construction and operation of a Chinese hatchery is less when compared to any other design for the same production capacity.In India, the Chinese hatchery system is now considered to be highly suitable for the production of quality fish seed.This system is designed for fish breeding and incubation.The duration of one operation for hatching is 4 days. It can be repeated after a period of 4 days.
Chinese type of Hatchery consists of four main components
1. Overhead Water Storage Tank
The floor of the tank should be 2.6 m above ground level.The inside dimension should be 5.5 x 2.7 x 2.2m and it should have a 30,000 litres capacity.Water supply to the overhead tank should be arranged by pumping water from an open well or a deep tube-well.The overhead tank is used to supply sufficient water for the spawning, incubation and storage tanks.A smaller overhead tank with a 5,000 litres capacity is also useful for this type of an operation.
2. Spawning Pond:
It is a circular masonry / concrete pond with an inside diameter of 8 m. It has 50 cubic metres of water holding capacity.The inside depth at the periphery is 1.20 m which slopes down to the centre at 1.50 m.A water supply line is laid along the outside of the wall and the inlet to the pond is provided at 14-16 places equally spaced and fixed at an angle of 45° to the radius of the tank using a 20 mm diameter pipe with a nozzle mouth, all arranged in one direction.These are fixed to the vertical wall and the nozzle mouth is flush with cement plaster face and near the bottom along the periphery of the pond.In the fitted through which, on opening the valve, fertilized eggs along with water are transferred into incubation pond for hatching.The water flows in the spawning pool create an artificial riverine condition for the fish to breed.The shower and a perforated galvanised iron pipe are useful to increase the dissolved oxygen and reduction of the temperature of the water. About 70 kg of males and 70 kg of females can be kept in the spanning tank which can yield 10 millions of eggs in one breeding operation.
3. Incubation Ponds:
There are two circular incubation ponds each of 3.6 m internal diameter.There are 2 chambers in each pond. The dimension of the outer chamber is 4 m having an outer masonry / concrete wall.Another circular wall with a fixed nylon screen is provided at 0.76 m clear distance from the outer wall.These tanks are about one metre in depth with 9-12 m3 of water holding capacity.They hold 70,000 million eggs / m3.The inner chamber is provided with 10 cm. diameter vertical outlets with holes at different heights for taking out excess of water of the incubation pond.The spawn along with water flows from these ponds to spawn collection pond.From the overhead tank, the initial 7.5 cm diameter pipe line is reduced to 5 cm diameter pipe line and then to 1.2 cm diameter pipe line.8 numbers of outlets are fitted in the floor of the incubation pond with each outlet having duck mouth opening fixed at an angle of 45° towards inner wall.All the outlets are fixed in one direction only.Water supply pipes are fitted from the circular spawning tank by a 10 cm pipe line which is then bifurcated into 2 pipelines off cm diameter each one for each of the incubation tanks which are further connected to duck mouth outlets in the floor of incubation ponds.There is an outlet of 7.5 cm diameter through which the hatchlings pass into the hatchling receiving pond. This opening is also used for complete dewatering of the outer chamber of the incubation pool. Desired water movement is about 0.2-0.3 m / sec.
4. Hatchling Receiving Pond:
This is a rectangular masonry concrete tank.The inside dimensions are 4 x 2.5 x 1.2 m. This is located at a lower elevation than the incubation pond, so as to drain out the water from it by gravity.Fresh water supply from the overhead tank is provided by a 7.5 cm diameter pipe line, bifurcated into 3 numbers of 3cm diameter pipelines. These pipelines are arranged to provide the spray for aeration.From each of the incubation ponds 7.5 cm diameter pipes are provided for transferring and regulating spawn intake into the spawn receiving pond.Hooks are fixed in two opposite side walls of the pond for fixing the net for the collection of spawn.Steps are also provided for getting into the pond for the collection of spawn. The overflow from this pond is discharged into an open drain and suitably utilised in the earthen ponds, if possible.
Operation of the Chinese Hatchery:
Brooders are kept in the spawning pond for about 4-8 hours for conditioning.Then between 4-6 PM, the first injection is given to the females.After 6 hours a second dose of injection is given to the female and one dose to the male.After 4 hours of the injection, the water jets are started so as to get the circular motion in the water.After 4-8 hours of the second injection, breeding takes place.One crore of eggs can be treated at a time in one operation.The eggs are collected from the bottom and are transferred into the incubation pools through pipes by opening the valves.Arrangements are made to chum the water again in the incubation pools.In 4 days time, the spawn is about 6 mm in size and then it is taken into the hatching spawn receiving pool.From there, it is lifted and stocked in separate water ponds until they reach the fry stage.If oxygen is less, aeration can be given through a compressor in the incubation pool at the rate of 6 kg / cm2 run by a 1 HP motor.For aeration water showers, water jets, etc can also be provided depending upon the requirement.During the breeding season lasting about 120 days in a year, the breeding and hatching operations can be carried out in about 30 batches, each batch of 4 days. About one crore eggs can be hatched in one batch and with a 95% hatching success, 285 million spawn of about 6 mm size can be produced.The main advantages are that the structures are of permanent nature. The hatchery is easy to operate and it needs less manpower.
Operation of the Chinese Hatchery