The Sex Ratio, Gonadosomatic Index, Stages of Gonadal Development and Fecundity of Sompat Grunt, Pomadasys jubelini (Cuvier, 1830)

The sex ratio, gonadosomatic index, stages of gonadal development and fecundity of sompat grunt Pomadasys jubelini off Lagos coast, Nigeria were investigated. P. jubelini had sex ratio of 1: 0.85 (male to female). The difference in sex ratio was not significantly different (p > 0.05) from the expected 1:1 distribution. Gonadosomatic index ranged from 0.07 to 7.29% with mean of 2.25 ± 0.08%. High gonadosomatic indices were recorded in July to September, which suggested the spawning period. Only three stages (quiescent, maturing and mature) of gonadal development were observed in male and female fish. Fecundity ranged from 10,550 to 65,248 eggs with mean of 35,744 ± 626 eggs. This indicated that P. jubelini is a low fecund fish. Fecundity and body length and fecundity and body weight were positively correlated. Fecundity-length relationship was Log F = 2.1766 + 1.8759 Log L (r = 0.2896) and fecundity-weight relationship was Log F = 3.7526 + 0.3719 Log W (r = 0.1985). Fecundity was more related to length than weight. P. jubelini is a total spawner which spawns during the rainy season in marine and estuarine environments. As a rainy season marine spawner, large total catch can be done during the spawning period and there is abundance of fish seeds, fry and larvae after this period. This makes it cost effective for fish farmers for production of P. jubelini by collection of fish seeds and fry from the wild. The results will increase our knowledge of reproductive biology of P. jubelini which is relevant for fisheries and aquaculture management as well as breeding programmes.