The influence of social factors on juvenile
sexual differentiation was explored in a diandric, protogynous
grouper Epinephelus coioides. Experimental social
units were established as singles, pairs and quartets using
sexually undifferentiated juveniles at an age of 22 weeks
post-hatching (WPH); all gonads were examined histologically
at 130 WPH, the age of first sexual maturation.
The percentage of primary males was about 39% at the end
of the experiment, higher than the 5% obtained under
mariculture conditions or from wild stocks for similar age
or body size. This study demonstrated for the first time that
social factors can significantly influence juvenile sexual
differentiation in E. coioides.