Change in the Known Ocean Distribution of Japanese Chum Salmon, Oncorhynchus keta, in Relation to the Progress of Stock Enhancement
New information on the ocean distribution of maturing Japanese chum salmon, Oncorhynchus keta, based on offshore tagging experiments conducted from 1956 to 1991 is summarized. Of 138 039 chum released in the North Pacific Ocean and its adjacent seas, 663 fish were recovered along the Japanese coast in the year of tagging and up to March of the next year. The distribution area of maturing Japanese chum indicated by these tag recoveries extended much further south and west than shown in previous studies. The central and western North Pacific Ocean now form important parts of the range. We conclude that extensive stock enhancement of chum in Japan is associated with enlargement of the known distribution area of maturing Japanese chum in the North Pacific Ocean.