Finfish Breeding and Hatchery Management

Egg and embryonic development

● The eggs are adhesive (attach to substratum), small (1-2 mm diameter), spherical with narrow perivitelline space  and pale-yellow
● Unfertilized eggs are opaque white.
● Compared to major carp eggs, these eggs develop at a slower rate
● The first cell division starts about 30 minutes after fertilization and after passing through several divisions reach morula stage in about 4-6 hours
● The eggs reach yolk-plug stage and  embryo indication in 6-8 and 8-10 hours, respectively
● The embryo starts twitching movement in 16-18 hours
● Advanced  embryo occurs in 30-36 hours when optic vesicles and pectoral fin rudiments appear
● There is a further increase in the number of myotomes, rapid twitching movement and the embryo is ready to hatch
● The eggs hatch in 36 – 72 hours at 26 – 31⁰C.
● 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.