Demographic characteristics of a selection of exploited reef fish from the Seychelles: preliminary study

The population biology of six commonly caught species in the Seychelles reef fisheries was investigated by the study of otolith microstructures. Alternating translucent and opaque bands were observed in transverse sections of sagittal otoliths from Epinephelus chlorostigma, Lethrinus lentjan, Lethrinus mahsena, Scarus ghobban, Scarus rubroviolaceus and Siganus sutor. Evidence derived from two tagged fish injected with tetracycline and recaptured after 1 year in the wild tentatively suggests that opaque bands are formed on an annual basis in the otoliths of L. mahsena. Species with a protogynous reproductive mode had significantly female-biased sex ratios overall, but the bias was removed in the older age classes apparently as a result of sex change. The results demonstrate that for S. ghobban and S. rubroviolaceus secondary males had accelerated growth rates, but the phenomenon was not implicitly associated with a protogynous mode of sexual development.