Abstract: The Southern Ocean ecosystem is highly susceptible to climate warming, yet the response of its dominant mesopelagic fish, Bathylagus antarcticus, remains inadequately quantified. Biotic interactions, particularly prey availability, are rarely incorporated into habitat projections, potentially biasing future risk assessments. This study aims to investigate the distribution and future dynamics of suitable habitats for B. antarcticus under climate change, as well as to analyze the underlying environmental and biological driving mechanisms. Based on the biomod2 ensemble modeling platform and spatial block cross-validation via the BlockCV package, we constructed species distribution models (SDMs) for B. antarcticus using environmental-only variables, as well as predator-prey models incorporating Euphausia superba and Metridia gerlachei as prey variables. Model performance was evaluated to select the optimal model for predicting current and future suitable habitat distributions. The predator-prey model incorporating E. superba as a prey variable achieved the best performance. Compared to the environmental-only model, it increased the mean TSS, mean AUC, and proportion of qualifying single models by 6.98%, 1.93%, and 14.78%, respectively, while improving the mean TSS and mean AUC of the ensemble model by 7.81% and 2.25%. Predictions indicated that the current suitable habitats of B. antarcticus are primarily distributed in the circum-Antarctic region south of the Southern Antarctic Circumpolar Current Front (excluding the Ross Sea and Weddell Sea). In the future, these habitats are projected to undergo poleward contraction. Under the SSP5-8.5 scenario by the end of the 21st century, the overall suitable habitat area is predicted to decrease by 23.89%. Habitat loss mainly occurs in the Lazarev Sea and lower-latitude circum-Antarctic regions, whereas the Ross Sea and Weddell Sea will emerge as new suitable habitats. The inclusion of prey variables enhanced model performance and stability, resulting in a more spatially and numerically concentrated distribution of predicted suitable habitats. This highlights an ecologically interpretable pathway driven synergistically by environmental factors and prey availability. This study provides a more accurate predictive basis for understanding the spatial responses of pelagic fish resources in the Southern Ocean to future climate change.