海洋生活初期のサケ・マス稚魚の生態に関する研究 ＩＩＩ 北日本の太平洋海域に出現する離岸期サケ稚魚の起源と回遊経路

Abstract

The origins and migration routes of migrating juvenile chum salmon Oncorhynchus keta along the Pacific coasts of Hokkaido and Honshu were examined on the basis of seasonal and geographical distribution data. Three groups of migrating juveniles were recognized in the survey area. The first group in the waters from Tsugaru Strait to Hidaka from late May to early June was suggested to originate from the Japan Sea area of northern Honshu or from Mutsu Bay, the second, occurring in large numbers off Hachinohe from mid-June to late June was suggested to be from the Pacific coast of northern Honshu. The third, occurring in large numbers along the Pacific coast of Hokkaido from early July to mid-July, was estimated to be composed of juveniles from the Pacific coast of Honshu and from nearby localities. The migration routes of the juveniles are considered to be along the coast, and offshore migrating juveniles of various origins are thought to migrate along the Pacific coast of eastern Hokkaido.