Bull. Jpn. Soc. Fish. Oceanogr. 78(1), Page 28-35, 2014   Catches of the Japanese common squid Todarodes pacificus and temperature environment in the northern Nemuro Strait Kenji Sakaguchi1, 2† 1 Hokkaido Research Organization, Kushiro Fisheries Research Institute, Hama, Kushiro, Hokkaido 085-0024, Japan 2 Present: Hokkaido Research Organization. † E-mail: sakaguchi-kenji@hro.or.jp Catches of the Japanese common squid Todarodes pacificus in the northern Nemuro Strait were examined with special reference to sea surface temperature (SST) around the area during the fishing season to understand the mechanisms underlying the aggregation of the squid in the strait. The 10°C isotherm of SST, regarded as the lower limit of the squid distribution, moved from the Sea of Okhotsk to the strait forming an inverted U-shape under the influence of the East Sakhalin and Oyashio Currents. A large amount of squid was caught by set nets at the deeper side of the steep slope in the strait, whereas a small amount was caught at the shallower side. Few squid seemed to migrate to the strait for spawning because of low maturation rates. Therefore, it was suggested that the squid in the Sea of Okhotsk were forced to gather and migrate to the strait because of decreasing water temperature and were aggregated between cold water and the steep slope or shallows in the strait that prevented them from migrating to the shallows. Key words: Hokkaido, Japanese common squid, Nemuro Strait, Sea of Okhotsk, SST, Todarodes pacificus