Aspects of the fecundity of the black-chinned tilapia Sarotherodon melanotheron in the Fosu lagoon, Ghana

Abstract

The black-chinned tilapia, Sarotherodon melanotheron (Pisces: Cichlidae), which dominated the Fosu Lagoon fishery, was exposed to pollution, siltation, fishing pressure, destructive fishing methods, and climate change. Samples of black-chinned tilapia were obtained with cast net, drag net and gill net, out of which 441 gravid specimen were randomly selected and dissected to remove eggs which were then counted. The absolute fecundity varied from 20 eggs to 370 eggs with a mean of 78 ± 33 eggs. Fish that had fecundity below and above the reported minimum of 200 eggs constituted 98.86 percent and 1.14 percent of the total sample, respectively, indicating that fecundity is below the minimum number of eggs the species is reportedly capable of producing. Positive, linear, weak and significant relationships were found between absolute fecundity and body parameters indicating that absolute fecundity is independent of body parameters, and could be influenced by biological, environmental, or anthropogenic factors. Condition factor ranged between 2.26 SL and 10.63 SL. Length at first maturity was 4.8 cm SL and 6.4 cm TL, respectively, confirming the precocious reproductive habit of the species. The size structure of the S. melanotheron population is dominated by small-sized fish of SL 7.0 – 7.9 cm (44.90 %) and 6.0 – 6.9 cm SL (32.65 %) ranges, which together accounted for 77.55 percent of the total sample. It is recommended that the fecundity and other reproductive parameters of the species be investigated during the dry and wet seasons in order to determine the reproductive potential and strategies for survival of the species.