Preliminary Records of Otolith-Marked Chum Salmon found in the Bering Sea and North Pacific Ocean in 2006 and 2007

We examined otolith marks on chum salmon caught in the North Pacific Ocean and Bering Sea during the spring and summer of 2006 and 2007. Otolith marks were detected in 190 of 8,295 immature and maturing fish. Of these marked salmon, 13 fish were found in the North Pacific Ocean and 177 fish were found in the Bering Sea. Approximately 90% of the marked salmon were released from Japanese hatcheries. Other marked fish originated from hatcheries in Alaska, Russia, and the Republic of Korea. Our results suggest that otolith-marked chum salmon released from NPAFC countries are detectable in the Bering Sea and North Pacific Ocean. Our study demonstrated that otolith marking is a useful tool for identifying hatchery of origin of individual chum salmon in the ocean. We believe this technique will be useful for the international management of anadromous salmon stocks.