Optimal fishing effort for commercial catfish (Clarias gariepinus) fishery in the southeast arm of Lake Malawi: A Gordon-Schaefer model approach

This study determines the optimal fishing effort for the commercial catfish (Clarias gariepinus) fishery in the southeast arm of Lake Malawi, with the aim of maximising economic benefits while maintaining a biologically sustainable fish stock. The study utilised secondary catch and effort data covering the period 2000-2023, together with secondary fish price and fishing cost data derived from the same previously published study. The Gordon-Schaefer (GS) model was used to estimate the static exploitation reference points of maximum sustainable yield (MSY), maximum economic yield (MEY), and open-access yield (OAY). Bifurcation analysis of the GS model showed that, for the continued persistence of the resource, fishing effort should remain below the bifurcation threshold of E = 6830 trips per year. The study further discusses the optimum sustainable yield (OSY), a dynamic exploitation level. Analysis of the exploitation reference points showed that the optimal fishing effort is approximately 445 trips per year, corresponding to the MEY reference point, which coincides with the OSY effort when the discount rate is zero. Since the observed fishing effort substantially exceeds 445 trips per year, the study recommends implementing management strategies aimed at reducing fishing effort to sustainable levels in order to ensure long-term biological and economic sustainability of the fishery.