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An update of the reproductive biology of sardinellas (Family: Clupeidae) in the coastal waters of Ghana
Isaac Kofi Osei, John Blay, Noble Asare
Aspects of the reproductive biology of the round sardinella Sardinella aurita and flat sardinella Sardinella maderensis, the most important small pelagic fishes in the coastal waters of Ghana are reported in this paper. The information presented here is of management value considering recent observations which indicate that the stock is nearing collapse from overfishing. Samples of fish were randomly taken from commercial landings at Elmina (5? 06′ N; 1? 23′ W) between October 2013 and September 2014. S. aurita measured 11.0 cm to 27.9 cm TL and S. maderensis 9.8 cm to 28.2 cm TL. Maturity size (Lm50) of S. aurita males was 16.34 ± 0.21 cm TL and females 16.55 ± 0.19 cm TL, and S. maderensis males and females matured at 15.33 ± 0.24 cm TL and 15.09 ± 0.98 cm TL, respectively. Analysis of monthly gonadosomatic index (GSI) and percentage of spawning fish suggested that S. aurita spawned from February or March to September, with a major activity in July - September and a minor spawning in February - May. S. maderensis similarly bred within these periods with a major spawning in September and a smaller peak in March. Ova from ripe ovaries of both species were bimodal in diameter frequency distributions suggesting occurrence of restricted spawning periods in the species. Fecundity of S. aurita varied from 4,834 to 63,917 ova in fish of 19.3 cm TL and 65.92 g body weight to 63,917 ova in fish of 25.7 cm TL and weighing 145.82 g. Fecundity of S. maderensis ranged from 7,597 ova in fish of 23.6 cm TL and 112.51 g to 33,984 ova in fish measuring 27.5 cm TL and weighing 187.48 g. From the fecundity-body size equations, S. aurita was found to be more fecund than S. maderensis, which might partly explain the higher productivity of the former in Ghana waters. This study provides first-time information on the biology of S. maderensis in Ghana waters.