article · PLoS ONE
Commercial catfish fishing in the southeast arm of Lake Malawi requires a major reduction in fishing activity to protect both fish stocks and economic returns. An evaluation of historical catch, effort, price, and operating cost data from 2000 to 2023 using the Gordon-Schaefer bioeconomic model established critical exploitation reference points. To ensure the fish population persists, fishing effort must remain strictly below a bifurcation limit of 6,830 trips per year. However, to maximise economic returns alongside biological sustainability, the optimal target is approximately 445 trips annually, corresponding to the maximum economic yield. Current fishing operations heavily exceed this optimum level. Aligning operational activity with this lower target through targeted fisheries management strategies is necessary to preserve the fishery as a biologically viable and profitable resource over the long term.
Overfishing threatens the stability of freshwater ecosystems and the livelihoods that depend on them. By identifying clear mathematical limits for biological survival and economic efficiency, this research provides concrete operational benchmarks. These figures show environmental regulators and fishing communities exactly how much pressure must be reduced to keep the Lake Malawi catfish industry profitable, secure, and biologically sustainable.
This research provides applied bioeconomic benchmarks directly relevant to fisheries authorities, resource managers, and commercial fishing cooperatives. While not a commercial product itself, the findings offer an evidence-based framework for setting fishing quotas, issuing vessel licences, and designing economic management programmes. The modelling is applied and tested on historical industry data, making it ready for adoption by policymakers seeking to balance fleet profitability with resource conservation.
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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.
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DOI: 10.1371/journal.pone.0343577
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