Domestication of the white grouper, Epinephelus aeneus 1. Growth and reproduction

The growth and reproductive biology of the white grouper, Epinephelus aeneus, were studied in captive fish to determine its potential for aquaculture. About 250 fish were captured by fishermen along the Mediterranean coast and maintained in 16 m3 concrete tanks supplied with sea water in a flow-through system. The captive fish fed readily on dry pellets supplemented with chopped frozen fish and gained an average of 3.3 g/day during the initial growth phase (0.5-1.5 kg), and 11.3 g/day during the secondary growth phase (1.5-3.0 kg). Using ovarian biopsies, the sexual development of 17 females was closely monitored for 3 years, and for 1 year in an additional 47 females. In adult females held in captivity, the oocytes reached the final stages of vitellogenesis, however, final oocyte maturation, ovulation and spawning did not occur. Sustained release of [-Ala6,Pro9NEt]-GnRH from implanted devices was highly effective in inducing ovulation, but did not result in natural spawning. Repeated implantations resulted in 2–3 ovulations per reproductive season, which lasted from April through September. The ovulated females were manually stripped and the eggs were artificially fertilized, resulting in millions of fertilized eggs and larvae. The average fecundity per female was 242 343 eggs (kg BW)−1 yr−1. In some of the young females, early vitellogenesis did not lead to the final stages of vitellogenesis. Instead, the vitellogenic oocytes underwent rapid atresia. Monitoring individual fish demonstrated that E. aeneus is a protogynous hermaphrodite, changing sex from female to male, confirming reports by other authors. Sex inversion occurred both spontaneously and after implantation with 17α-methyltestosterone. The rapid growth rates and the potential for induced spawning in captivity make the white grouper an excellent candidate for mariculture