A survey of mtDNA variation among populations of chum salmon Oncorhynchus keta around the Pacific Rim revealed four large population groups: Rim of the Sea of Japan, the Rim of the Okhotsk Sea and West Bering Sea, North‐west Alaska and Gulf of Alaska. The observed population structure appears to reflect isolation by distance with limited gene flow between regions and larger amounts of gene flow between populations within these...

Eight temperature‐recording data storage tags were recovered from three salmonids in Alaska (pink and coho salmon and steelhead trout) and five chum salmon in Japan after 21–117 days, containing the first long‐term records of ambient temperature from Pacific salmonids migrating at sea. Temperature data imply diel patterns of descents to deeper, cooler water and ascents to the surface. Fish were found at higher average temperat...