Evaluation of biomass and exploitation status of Bigeye grunt and Lesser African threadfin fisheries in the Eastern Central Atlantic Ocean using a data-limited biomass dynamic model (CMSY++)

The Bigeye grunt (Brachydeuterus auritus) and Lesser African threadfin (Galeoides decadactylus) underpin food security and livelihoods in the Eastern Central Atlantic Ocean, yet robust stock assessments remain scarce for the northern stock (NS) region delineated by the Committee for the Eastern Central Atlantic Fisheries (CECAF). This study applied the Bayesian Catch-Maximum Sustainable Yield (CMSY++) catch-only model to Food and Agriculture Organization FishStatJ catch data (2001–2021) for Guinea-Bissau, Guinea, Sierra Leone, and Liberia. The study aimed to (1) assess the predictive accuracy of CMSY++ under four biomass-prior (b/k) scenarios, and (2) estimate the status of both stocks. From the results, the expert-informed prior yielded the most reliable estimates: Bigeye grunt exhibited sustainable biomass above the Maximum Sustainable Yield (i.e., B/BMSY >1.0), fishing mortality below the Maximum Sustainable Yield threshold (i.e., F/FMSY< 1.0), and a high intrinsic growth rate (i.e., r ≈ 0.6 per year). Conversely, Lesser African threadfin was overexploited and depleted (B/BMSY ≈ 0.6, F/FMSY ≈ 2.6, r ≈ 0.4). These findings affirm CMSY++ as a valuable tool for data-limited fisheries, contingent on expert-informed priors, and underscore the urgent need for precautionary management of Lesser African threadfin to promote stock rebuilding and long-term sustainability.