Experiments on broodstock development and spawning of Epinephelus tauvina (Forskal)

Abstract

The present paper reports on broodstock development and spawning of the
greasy grouper Epinephelus tauvina in indoor 5 ton capacity FRP tanks in
recirculating sea water system, under controlled conditions. The broodstock was
developed in the culture system by rearing the wild fingerlings, caught in the
size range 90 to 200mm. After attaining maturity, the fishes were fed with
supplementary diet for developing them into mature females. Simultaneously,
a few were administered the male hormone methyltestosterone (MT) for sex
inversion to males. Mature spermiating males were developed by this technique.
A mature female fish weighing 3.85 kg and a single spermiating male weighing
3.25 kg have spawned spontaneously in the same indoor tank consecutively for
two days from 29-10-1998 to 30-10-1998 and also from 20-12-’98 to 23-12-’98,
producing approximately 2,50,000 eggs in each spawning. On both the occasions,
the same hormonally sex inverted male has spermiated. Fertilization
rate was over 90%. Eggs measured 0.920 mm with a single oil globule. The eggs
hatched out at 23 hours. Hatching rate observed in the first spawning was 60%
and in the second instance, 45%. Newly hatched larvae measured 1.74mm. After
68 hours the larval mouth has opened and feeding has started.