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Abstract

During the migration of chum salmon (Oncorhynchus keta) towards the Shiretoko Peninsula in Hokkaido, Japan, the convergence of coastal currents results in the formation of intricate water temperature structures. However, the impact of this phenomenon on the behavioral tendencies of chum salmon remains largely unexplored. In 2012 and 2013, we conducted a study to document the vertical water temperature profiles and uninterrupted swimming patterns of homing chum salmon in the coastal waters surrounding the Shiretoko Peninsula. The results indicated that chum salmon exhibited a preference for avoiding thermoclines characterized by rapidly decreasing water temperatures. They were predominantly observed swimming either in the surface or deep seawater layers (210–230 m), away from the thermocline. This finding demonstrates that homing chum salmon adapt their behavioral patterns in response to the vertical temperature distribution in the water. The findings presented in this study contribute to our understanding of the swimming behavior of chum salmon, providing valuable insights that can be utilized to develop effective management strategies aimed at enhancing sustainability.

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