Reproductive biology of the blackchin tilapia ( Sarotherodon melanotheron) in the marine protected area of NiamoneKalounayes (Casamance estuary, Senegal)

Knowledge of the reproductive biology of fish is essential for the local fish population management in marine protected areas. The objective of the present study is to determine the sex ratio, reproductive period, and sexual maturity size classes of the blackchin tilapia (Sarotherodon melanotheron) in the marine protected area of Niamone-Kalounayes, located in Casamance, Senegal. A total of 471 individuals including 305 females and 166 males were sampled from June 2021 to July 2022, using an experimental beach seine (250 m long, 25 mm side mesh). The sex ratio (M: F = 1.0: 1.8) was in favor of females. The size at first sexual maturity (Lm50) was obtained 11.00 cm for males and 11.71 cm for females. The seasonal variation in the gonadosomatic index (GSI) indicates that this population has an extended reproduction period, ranging from March to September, with a clear peak in March, followed by a period of sexual rest (October-December), and a period of maturation of the gonads from January through March. Results of this investigation provided insights for better management practices for this specie.