Finfish Breeding and Hatchery Management (2+1)

Chinese hatchery

● Breeding and hatching devices of circular  shape and are of  Chinese origin are referred to as Chinese type of carp hatchery or eco-hatchery.
● It is here that fish are bred, eggs hatched and hatchlings produced.
● These tanks are made of brick or concrete or FRP, circular and their diameter varies from 6 to 12 m with a depth of 1.0 – 2.0 m.
● The base of the tank is sloped towards the centre where the central outlet is located
● They are provided with water jets/inlets on the bottom or inner-surface of the tank so as to provide a circular motion of water which results in better spawning and hatching than hapa system
Breeding tank : For the induced breeding of major carps, clean the breeding tank, fill it with clean water taken from a channel or well and release injected brooders up to 100 kg for spawning. 
● Provide water shower on the tank to maintain temperature and increase oxygen content
● Maintain a water flow rate of 200-250 L per minute to create a riverine environment and stop water flow just before the fish starts spawning.
● After spawning, remove the brooders, disinfect them and transfer to a freshly prepared pond.
● Collect the developing eggs and incubate in the hatching tank.
Hatching tank : The working principle of the hatching tank is more or less similar to that of  the breeding tank, excepting that it slightly smaller (3-6 m diameter and 1-1.5 m deep) and has two chambers, i.e. inner and outer
● The outer chamber has 3-6 m diameter, whereas the inner chamber has 1-1.5 m.
● The bottom of the outer chamber is provided with 15-20 water jets/inlets, equidistant from each other, to provide circular motion and simulate riverine environment.
● The circular wall that separates the outer chamber from the inner  chamber is covered with a nylon screen (mesh size 1/80)
● The nylon screen allows the water to flow from the outer chamber to the inner  chamber and prevent the escape of eggs and hatchlings
● The water comes out from the inner  chamber through a centrally placed vertical  pipe
● Maintain a water flow rate of 80-100 L per minute to provide a circular motion of water in the outer chamber

Operation :
● After cleaning tank and filling water, release about 7-10 lakh eggs/m³ of water.
● Ensure that the eggs keep bobbing up and down throughout the incubation period.
● The water flow should be such that the eggs keep away from the screen and do not hit against the outer wall.
● Hatching is almost 100% and hatching period is temperature dependent and varies between  16 and 20 hours
● Allow the resultant hatchlings to remain in the hatching tank for 3-4 days after which they are sold or transferred to nursery pond.
● Sprinkle KMnO₄ solution intermittently on the water to reduce siltation and microbial load
● Suspend a few coir ropes in the water column to remove dead eggs and spawn which stick to the bristles
● Clean and disinfect the tank thoroughly with KMnO₄ solution (5 ppm) after every cycle.

Merits :
1. Adaptable to very large-scale operation
2. Provides aspects of riverine environment
3. Hatching is very efficient
4. Water quality can be controlled
Demerits :
1. Requires a large quantity of water
2. Separation of egg shells from hatchlings is cumbersome
3. Repair is difficult
4. Expensive to install