Gonad stage: Males and females were classified in four gonad stages: Inmature and early mature (%N); mean and total maturity (%N); partial aand total spawning; reversion. Classification was made after histological examination of Bouin-preserved gonad samples. Tissue embedded in paraplast wax after dehydration, sectioned at 7 µm and stained with hematoxylin-eosin for examination.