A highly efficient method of inducing sex change using social control in the protogynous orange-spotted grouper (Epinephelus coioides)

摘要

In this study, a highly efficient method of inducing sex change using social control in the protogynous orange-spotted grouper (Epinephelus coioides) was developed. A series of experiments were carried out to investigate the influence of social unit size and seasonality on the rate of sex change rate in the orange-spotted grouper. The results revealed that the removal of male fish in social units with three females during the pre-breeding and breeding seasons was the fastest method ever recorded for inducing an artificial sex change in orange-spotted grouper. The data indicated that a sex change generally occurred in the largest female in the social unit. A sharp increase in levels of androgen and cortisol in serum are proposed as a marker of the onset of a female-to-male sex change. Using the method described in this study, a sex change from female to male occurred within two to four weeks of removing males from the social unit. To examine sperm fertility, the fertilization rate of males obtained by induced sex change was analyzed. The results revealed that males obtained by this method can successfully fertilize mature eggs. This method could address the scarcity of male groupers required for spawning in captivity, and would promote the development of grouper aquaculture.