Length based-stock assessment and Spawning Potential Ratio (LB-SPR) of exploited tilapia species (Coptodon zillii, Gervais, 1848) in Lake Volta, Ghana

Abstract

Length based stock assessment parameters and LBSR of C. zillii in Lake Volta were investigated for the purpose of sustainable management. The lengths of 517 individuals were measured from the lake from January to December 2020 and analyzed using TropFishR. The von Bertalanffy parameters including asymptotic length (L∞), growth rate (K), and growth performance index (Φ) were estimated as 30.4 cm, 0.38 per year, and 2.73 respectively. Total mortality rate (Z), natural mortality rate (M) and fishing mortality rate (F) were 4.58 per year, 0.89 per year and 3.96 per year respectively. The exploitation rate (E) was highly above the exploitation rate at the maximum sustainable yield (Emax) which shows that the fishery of the stock is facing high unsustainable fishing pressure. Based on the findings of the study, it is recommended that fishing pressure be reduced and, mesh size regulation be strictly enforced to ensure sustainability of the stock.