Characterization of salmon‐foraging harbor seals ( <i>Phoca vitulina</i> ) in the Erimo region, Hokkaido, Japan, using finite mixture models

Abstract The increase in the population of harbor seals ( Phoca vitulina ) in the Erimo region of Hokkaido, Japan, has coincided with rising fishery conflicts, affecting salmon setnets in particular. While seal‐related fishery damage has been reported, quantitative evidence of seal predation on salmon has been lacking. The present study employed a finite mixture model clustering method to analyze seal feeding patterns. This analysis revealed 13 distinct clusters, with one cluster specifically characterized by salmon predation. This cluster consisted primarily of larger individuals who obtained most of their daily energy requirements from salmon. In such an environment, seals may learn of setnet structures and fish aggregation characteristics, potentially increasing their dependence on these artificial structures. However, many seals in the population were not feeding on salmon, and the findings demonstrate that only a specific subset of the population, characterized by larger body size and older age, has developed specialized feeding strategies centered on salmon predation at setnets. This adaptation to setnet environments has significant implications for both fishery management and seal conservation in the region.