Habitat suitability of Thunnus spp. in the Northern South China Sea based on the MaxEnt species distribution model

Abstract

Tuna (Thunnus spp.) are apex predators and vital fishery resources in the Northern South China Sea. This study assesses the habitat suitability of tuna (Thunnus spp.) in the northern South China Sea using the MaxEnt model to analyze seasonal shifts and key environmental drivers from 2016 to 2020. Tuna occurrence data from the Guangdong Fishery Resources Data Collection System, along with environmental variables (Chlorophyll-a, sea surface salinity, sea surface height, and temperature), were utilized. Model performance was validated using the AUC and verified with catch per unit effort (CPUE) data. The model demonstrated a satisfactory predictive performance, with AUC TRAIN values ranging from 0.805 to 0.864, AUC TEST values from 0.795 to 0.839. Chl-a was the primary driver in spring, whereas SSS had a greater influence in autumn, with optimal SST ranging from 24 °C to 27°C. Suitable habitat (HSI > 0.8) reached its highest spatial coverage in April (7525 km²) and September (9656 km²), aligning with increased CPUE values during those periods. The model effectively captured seasonal variations in the species' spatial distribution; further refinement using additional predictors may lead to more accurate predictions. These findings provide important insights for adaptive fisheries management, supporting informed responses to climate-driven changes and promoting the future sustainability of regional tuna populations.