Bull. Jpn. Soc. Fish. Oceanogr. 78(3), Page 176-186, 2014   Distribution and migration of the Japanese sardine in the Sea of Okhotsk Kazunori Kuroda1† 1 Formerly, Tokai Regional Fisheries Research Laboratory, Fisheries Agency † E-mail: kuroda121625@ivy.ocn.ne.jp Northern marginal distribution of the Japanese sardine Sardinops melanostictus (Schlegel, 1846) in the Sea of Okhotsk has been reviewed in relation to migrations based on data in the 1930s and 1980s when the stock was abundant. Major results were as follows. 1) Sardine along the Okhotsk Sea coast of Hokkaido was caught during July to October in the 1930s with a peak in 1937, and during June to November in the 1980s with a peak in 1989. Over 80% of fish shoals in the Soya Warm Current occurred from June to July, and afterwards migrated to form the fishing grounds near the Kunashiri Strait. 2) The sardine was thought to immigrate to the Sea of Okhotsk from the Soya Strait and Kunashiri Strait and formed early fishing grounds near the Kunashiri Strait from June to July. 3) From August to September the sardine widely migrated northwards in the offing of the Sea of Okhotsk and approached the fishing grounds off southeastern Sakhalin. 4) In October, when the Soya Warm Current becomes weak and the East Sakhalin Current flows southwards, the sardine might migrate southwards and emigrate from the Soya and Kunashiri Straits until November. 5) It is clear that the Pacific and Tsushima Warm Current subpopulations of the sardine immigrate or emigrate mainly through the Soya or Kunashiri Straits, although the sardine mainly immigrated from the Soya Strait during 1986 to 1990, then gathered at a fishing ground near the Kunashiri Strait, and migrated widely to southeastern Sakhalin. 6) Comparing with the Pacific saury migrating to the Sea of Okhotsk, it was supposed that the mechanisms of immigration and emigration, and the migratory patterns of the sardine resemble those of the Pacific saury although these two species have different properties from each other. Key words: sardine, distribution, migration, the Sea of Okhotsk