Finfish Breeding and Hatchery Management

Unit 6 - Breeding of common carp

6.4. Hatching of eggs

• The developing eggs which are attached to the substratum are transferred to hatching hapa or circular tank for hatching where running water is maintained.
• The eggs are adhesive, small (1-2 mm diameter), with narrow perivitelline space, spherical and pale-yellow (fertilized).
• Unfertilized eggs are opaque white.
• The stocking density of eggs is 50,000 - 1,00,000 eggs per hapa (2 x 1 x 1 m) or 25-30 lakh eggs per circular hatching tank.
• The eggs hatch in 36 – 72 hours 26 – 31^oC.
• The newly-hatched spawn is heavy (remain attached to hapa wall), 4-5.6 mm long, with prominent eyes.
• The yolk-sac spawn remains in the hapa or tank till it becomes free-swimming.
• Yolk-sac is completely absorbed in 3-4 days.
  

Rearing of spawn

• After the yolk-sac absorption, the spawn is transferred to a prepared nursery pond for on-growing to fry/fingerling stage.
• In the nursery pond the spawn is fed with a mixture of rice bran and oil cake (1:1 ratio) till they reach fry stage in 15-20 days.