aquatic animal diseases, health care & management © tanuvas, 2011 visit to organized hatchery...
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Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
Visit to organized hatchery
Contents
• Components of a fish hatchery
• Brood fish ponds
• Breeding tanks
• Fish hatching tanks or system
• Vertical jar hatchery
• Hatching hapa
• Nursery tanks
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
An organized has the following components• Brood fish ponds• Spawning tanks/Breeding tanks / Breeding hapas • Hatching Tanks /jars /Hapa• Nursery tanks / systems to rear the postlarvae of fishes to fry stage
Components of a fish hatchery
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
• Brood fish ponds also called as brood fish holding tanks are used to hold adult fish for spawning /
to hold the donors of pituitary glands / to maintain the spent males and females after spawning.
• These ponds may be large rectangular earthern ponds or circular cisterns made of cement.
Brood fish ponds
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
• These tanks are used for the spawning of the fishes .
• Circular cement cisterns ,breeding hapas made with the net enclosures in big ponds are used for breeding of fishes.
• The eggs or spawn are transferred to the hatching units where the eggs hatch and the spawns are released .
• Circular cement spawning pools (8 m diameter) with 50 cubic metres of water holding capacity are used.
• The bottom of the pool slopes to the centre, where there is an outlet pipe (10 cm diameter) leading to the incubation
pond (egg collection chamber).
• The wall of the spawning pool is provided with diagonally fitted inlet pipes at an angle of 45 o for circulation of water
creating artificial riverine conditions.
• After circular pool is filled with water, about 80 kg of females and 80 kg of males are released into the pool.
• When the breeders start coming up to the surface, the valves are opened so that a circular current is created.
• The speed of water current is maintained at about 30 m/min. The yield of 10 million eggs per breeding operation is
usually achieved
Breeding tanks
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
Breeding HapasCircular breeding tanks
Breeding tanks
Aquatic animal diseases, Health care & Management
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Fish Hatching Tanks or systems • The hatching techniques of carps eggs have undergone a lot of changes to
get better hatching and survival from the earthen hatchery pits and cement hatchery pits at spawn collection centres.
• Circular Chinese hatchery are very popularly used for hatching and rearing of fishes.As spawning goes on in the breeding or spawning pool, the fertilised eggs are led into the hatching or incubation pool (3 m diameter - double walled circular pool, with inner wall of regulated mesh permitting outflow of water) where water at a regulated speed enters through the duck mouth valves fitted on the floor of the outer chamber. The speed of the water is regulated @2.5 litre/sec in the initial stage and then reduced to 2.0 l/sec when movement of embryo inside the eggs starts.
• After hatching, the speed is again increased to 3.0-3.5 l/sec. and the hatchlings are allowed to remain there for about 3 days till the yolk sac is absorbed.
• The Chinese hatchery system is meant for incubating very high density of eggs i.e. 7,00,000–12,00,000 eggs per cubic meter and provided with running water. This consists of hatching trough/cistern with filtering screen, nozzles, water inlet and outlet valve and fry collecting compartment
Fish Hatching Tanks or systems
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
Vertical jar hatchery
• In a vertical jar hatchery, hatching jars with a capacity of
6.0 to 6.35 litres, 50,000 eggs can be kept and a rate of
flow of water is maintained at 600–800 ml per minute for
Indian major carps and 800–1000 ml for silver carp and
grass carp. In hatching jars of higher capacity more eggs
can be introduced but the flow of water has to be suitably
increased. The hatching time inside the hatchery is nearly
2–3 hours less than in the field.
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Aquatic animal diseases, Health care & Management
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Hatching hapa• Under field conditions, the eggs are kept in double-walled hapas, outer made of this close-meshed cotton
or nylon and inner made of thin round-meshed mosquito net.
• The inner hapa is smaller, leaving gaps of 15 cm on all sides and also at bottom between the inner and
outer hapa. In an outer hapa of the size 2 m × 1 m × 1 m and a suitable size inner hapa a total number of
50,000 to 100,000 eggs can be kept for hatching depending upon fertilization. The eggs are distributed in
the inner hatching hapa uniformly.
• The hatching time is 16–18 hours in the case of Indian major carps and nearly two hours more in silver
carp and grass carp at optimum water temperature range of 26–31°C.
• The hatchlings pass through the inner hapa to outer hapa and inner hapa is removed.
• Inner hapa with wooden frame is found quite convenient for uniform distribution of developing eggs.
Floating hapas are also used for hatching purpose.
Aquatic animal diseases, Health care & Management
© TANUVAS, 2011
NURSERY TANKS
• Small nursery tanks made of cement cisterns or hapas made of net enclosures constructed in the ponds would serve as the nursery systems.
• In nursery ponds the fry usually grow to a size of 25–35 mm in about a fortnight with more
than 70–80% survival, when they become ready for harvesting.
• Harvesting is done by seining the pond water using a close meshed (1.45 mm) drag net.
Several netting operations should be done to ensure near total harvesting of the stock.