Captive maturation, spawning and larval rearing of seabass
Maturation of the captive broodstock was observed during the period from May to November in the RCC tanks and up to February in the recirculation system. Oozing males and gravid females with an ova diameter of about 400μm could be obtained. During this year, successful spawning was observed in ten of the twelve trials conducted in RCC tanks and 6 spontaneous spawnings were observed in the recirculation facility during the months of July August. Induced spawning was achieved in the months of September and October by intramuscular LHRHa hormone administration at a dose of 60 -70 μg/kg body weight in the case of females and half the dose in the case of males. The total number of eggs spawned in the natural spawning ranged from 0.3 to 1.7 million eggs with a fertilization rate from 58- 95 % and hatching rate of 60 - 92 %. In the induced spawning trials, the number of eggs spawned ranged from 0.25 to 1.0 million eggs with a fertilization rate of 38 - 86 % and the hatching rate ranged between 45 - 86 %. Of the 10 spawnings, a second spawning was observed in six. Though the fertilization rate was less in the second spawning, no differences were observed in terms of the number of eggs/ hatching percentage between the fi rst and second spawning. Hatchlings obtained either from natural or induced spawning was further reared under controlled conditions following the protocols standardized earlier.
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