Stock Distribution Patterns of Chum Salmon in the Bering Sea and North Pacific Ocean during the Summer and Fall of 2002-2004

Stock origin and ocean distribution of chum salmon in the Bering Sea and its adjacent North Pacific waters during the summer and fall of 2002-2004 were estimated using a mitochondrial DNA control region. The percentage of immature chum salmon samples was more than 97% in the fall of 2002 and 2003, and 80-88% in summer 2003 and 2004. The genetic stock identification (GSI) and GSI-estimated CPUE (catch per unit effort) suggested that immature chum salmon were mostly from Japanese and Russian stocks, and they were widely distributed in the Bering Sea. The abundance of North American stocks was much lower than that of Asian stocks in the Bering Sea, while it increased in the North Pacific Ocean in the fall of 2003. In the central Bering Sea, Japa - nese chum salmon stocks were most predominant among regional stocks. All regional stocks were distributed in proportion to sea surface temperatures (6.6-11.9°C) available during each survey period. The distribution pattern and abundance of chum salmon CPUE in the Bering Sea was different among years and seasons, while those changes were not significantly related to the favorable sea surface temperature range in the Bering Sea.