Potential habitat prediction and ecological niche differentiation of Trachurus murphyi and Engraulis ringens

Trachurus murphyi and Engraulis ringens are two representative and economically important pelagic fish species in the Humboldt Current System, and their spatial distribution patterns and niche differentiation directly influence regional fishery resource structure and interspecific relationships. To investigate the differences in potential suitable habitats and patterns of niche differentiation between the two species, we applied an ensemble species distribution modeling approach (BIOMOD2 v4.2.6) by integrating species occurrence records with multiple oceanographic environmental variables to predict the spatial patterns of potential suitable habitats, and further quantified the niche volume and niche overlap using an ecological niche hypervolume framework. The models exhibited high predictive performance (T. murphyi: AUC=0.99, TSS=0.94; E. ringens: AUC=0.99, TSS=0.96). Mixed layer depth, dissolved oxygen, and primary productivity were identified as the key environmental factors shaping the distribution of potential suitable habitats for the two species. Both species preferred areas with mixed layer depths shallower than 50 m; however, E. ringens was more dependent on high primary productivity and could tolerate lower dissolved oxygen conditions, whereas T. murphyi exhibited higher habitat suitability in relatively low-productivity environments. Their highly suitable habitats were mainly distributed between 15°S and 45°S, with partial spatial overlap. Ecological niche hypervolume analysis indicated that T. murphyi had a larger niche volume, and the niche overlap degree between the two species was moderate-to-high (Sørensen=0.616, Jaccard=0.445). The study demonstrates that the two species achieve niche differentiation through differential responses to key environmental variables, thereby maintaining coexistence in overlapping regions. The result provides a scientific basis for the rational exploitation and ecosystem-based management of pelagic fish resources in the southeastern Pacific Ocean.