Abstract

Two mature female cobia, Rachycentron canodum, injected with a single dose of human chorionic gonadotrophin (HCO) at 275 UI/kg of body weight, and one non-injected ripe male spawned spontaneously in captivity. Oocytes aspirated from each female prior to injection were maturing vitellogenic oocytes nearing the final oocyte maturation (FOM) stage and averaged 625 µ in diameter. Both females spontaneously spawned ~ 42 hours post-injection; spawned oocytes ranged 1.1 - 1.3 µ in diameter. Fertilized eggs hatched ~26 hours later. Estimates for number of eggs spawned (both females combined) and hatched were 3.2 million and 320,000, respectively. Aspects of embryogenesis and larval growth/development were observed. Critical survival period for larvae was day 3 at which time termination of yolk sac absorption occurred and first feeding commenced. Enriched rotifers, wild zooplankton, and artificial food were offered larvae during larval rearing treatments. Larvae contained in a black tank and fed a high density diet of enriched rotifers exhibited highest survival and were reared through day 13, post-hatch. The study documents the spontaneous spawning of wild-caught male and female R. canodum from the Gulf of Mexico, and provides comments on fertilization, hatching and larval development. Results of the study strongly suggest that R. canodum exhibits potential as an aquaculture species.

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