1Fishery Research Agency, Yokohama, Kanagawa 220-6115, 2Goto Station, Seikai National Fisheries Research Institute, Fishery Research Agency, Goto, Nagasaki 853-0508, Japan
The population structure of Pacific herring Clupea pallasii caught in the coastal waters around Funka Bay, southern Hokkaido, was investigated by comparing recaptures of tagged juveniles and adults and catch in weight of herring around Funka Bay. Juvenile and adult herrings tagged and released in the coastal waters of northern Honshu were recaptured around Funka Bay during spring and autumn. Catches of herring around the bay were large during spring and autumn before 1991, but peaked in winter after 1999. Herring caught during spring and autumn around the bay seemed to be composed of feeding groups immigrating from northern Honshu. The increase in catches in winter after 1999 was supposed to have been caused by the increase of local population in the coastal waters around Funka Bay.