Divergent drivers of fish habitat suitability in the Yangtze River Estuary: environmental filtering versus prey availability

Abstract The spatial distribution of estuarine fish communities is shaped by both abiotic environmental factors and biotic processes. However, traditional Species Distribution Models (SDMs) often overlook critical biotic factors, including predation, competition, and prey availability, limiting predictive accuracy and ecological interpretability. This study examines two representative fishes from the Yangtze River Estuary (YRE): the small benthic marine fish Collichthys lucidus and the large freshwater predator Leiocassis longirostris . Using an ensemble modeling approach integrating seven individual models, we developed three modeling frameworks: (i) SDM_ A , including only environmental variables; (ii) SDM_ B , integrating prey resources; and (iii) SDM_ MB , further incorporating predator variables. We evaluated how prey and predator factors influence habitat suitability modeling for typical estuarine fishes. Results show that prey resources were the main determinant of C. lucidus distribution, and adding abundance-based prey and predator variables (prey1, prey2, and predator) improved model performance. In contrast, L. longirostris was less affected by biotic variables and primarily constrained by salinity, temperature, and other environmental gradients. Moreover, SDM_ MB achieved superior spatial discrimination across all seasons, particularly in typical estuarine transition zones and areas with high prey abundance. This study highlights the importance of considering biotic variables that reflect the ecological differences among functional groups when modeling species distributions in estuarine environments.