CPUE standardization for Ethmalosa fimbriata (Bowdich, 1825) and Galeoides decadactylus (Bloch, 1795) using species distribution model Template Model Builder (sdmTMB) off the Central Gulf of Guinea

The Central Gulf of Guinea supports critical marine fisheries that sustain livelihoods and food security for millions of people in West Africa. This study presents the first standardization of nominal catch per unit effort (NCPUE) for two commercially important species: the small pelagic Ethmalosa fimbriata (bonga Shad) and the demersal Galeoides decadactylus (lesser African threadfin, LATF), using the sdmTMB spatiotemporal modeling framework. NCPUE served as the response variable, with key environmental predictors including sea surface temperature (SST), sea surface salinity (SSS), chlorophyll-a (Chlor-a), ocean surface wind (OSW), and dissolved oxygen (DO₂). Five best-fit models were selected based on Akaike Information Criterion (AIC). For bonga shad, the optimal model included SST, Chlor-a, SSS, and DO₂. For LATF in the Cameroonian EEZ, separate models were selected for daily and vessel-based NCPUE incorporating combinations of SSS, OSW, DO₂, and Chlor-a. In the Nigerian EEZ, a model including SST, SSS, OSW, and DO₂ standardized both daily and vessel NCPUEs. The standardized CPUEs values were extracted using the predict() function in the spatiotemporal model fitted with the sdmTMB. All models accounted for major environmental variability, yielding standardized CPUE indices that better reflect fishing pressure. These standardized CPUEs showed moderate to strong negative correlations with fishing effort, indicating successful adjustment for environmental effects. The results provide a robust baseline for stock assessment and contribute to improved fisheries management in data-limited contexts across the Gulf of Guinea. • First application of the sdmTMB model to standardize CPUE for Bonga shad and Lesser African Threadfin in the central Gulf of Guinea. • All five final models accounted for environmental variability, resulting in smoother CPUE trends. • Standardized PUEs provide a reliable basis for stock assessment and fisheries management decisions.