Overexploitation and urgent need for precautionary management of Bonga Shad ( Ethmalosa fimbriata ) in West African waters: A multi‐model Bayesian assessment

Abstract

Ethmalosa fimbriata, a key small pelagic species underpinning food security and livelihoods along the West African coast, warrants a robust stock assessment due to concerns of overexploitation. This study synthesizes multi-fleet catch records (1970-2021) and unstandardized catch per unit effort (CPUE) data (1995-2017) from the Eastern Central Atlantic (ECAO) to evaluate the northern stock using four surplus production models: the catch-only (CMSY) and abundance-only (AMSY) maximum sustainable yield models, the Bayesian state-space model (BSM) and the Just Another Bayesian Biomass Assessment (JABBA) model implementing Schaefer, Fox and Pella-Tomlinson functions. The objective was to evaluate model predictive accuracy and stock status to provide evidence-based management advice. From the results, CMSY indicated 2021 biomass (B) was marginally above the sustainable limit (B/BMSY ≈ 1.03) with current fishing mortality (F) near FMSY, while AMSY and BSM both indicated ongoing depletion (B/BMSY ≈ 0.56-0.81) and overfishing (F/FMSY >1.0). JABBA's Schaefer model, demonstrating superior fit (root-mean-square error = 16.9%, Deviance Information Criterion = -382.7) over Fox and Pella-Tomlinson models, estimated 2021 biomass at 9% below BMSY and fishing mortality at 59% above FMSY. Fox and Pella-Tomlinson models yielded similar biomass trajectories but were less precautionary. Projections indicate that only Schaefer-based total allowable catches (TACs) below 100,000 t would stabilize biomass; higher quotas risk continued decline. Despite limitations including incomplete catch data and reliance on unstandardized indices, results underscore the urgency for precautionary catch limits, regional coordination and improved compliance to ensure sustainability. This study offers a transferable assessment framework for data-limited fisheries and supports evidence-based policy for the conservation of E. fimbriata and food-security resilience in West Africa.