DOMESTICATION OF THE WHITE GROUPER, EPINEPHELUS-AENEUS .1. GROWTH ANDREPRODUCTION

The growth and reproductive biology of the white grouper, Epinephelus aeneus, were studied in captive fish to determine its potential for aq uaculture, About 250 fish were captured by fishermen along the Mediter ranean coast and maintained in 16 m(3) concrete tanks supplied with se a 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/da y during the secondary growth phase (1.5-3.0 kg). Using ovarian biopsi es, the sexual development of 17 females was closely monitored for 3 y ears, and for 1 year in an additional 47 females. In adult females hel d in captivity, the oocytes reached the final stages of vitellogenesis , however, final oocyte maturation, ovulation and spawning did not occ ur. Sustained release of [D-Ala(6),Pro(9)NEt]-GnRH from implanted devi ces was highly effective in inducing ovulation, but did not result in natural spawning. Repeated implantations resulted in 2-3 ovulations pe r 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 s ome of the young females, early vitellogenesis did not lead to the fin al stages of vitellogenesis. Instead, the vitellogenic oocytes underwe nt rapid atresia. Monitoring individual fish demonstrated that E. aene us is a protogynous hermaphrodite, changing sex from female to male, c onfirming reports by other authors. Sex inversion occurred both sponta neously and after implantation with 17 alpha-methyltestosterone. The r apid growth rates and the potential for induced spawning in captivity make the white grouper an excellent candidate for mariculture. (C) 199 7 Elsevier Science B.V.