Bull. Jpn. Soc. Fish. Oceanogr. 79(2), Page 43-51, 2015   Method to forecast the catches of Japanese common squid Todarodes pacificus in the Sea of Okhotsk off Hokkaido Kenji Sakaguchi1† and Norio Yamashita2 1 Hokkaido Research Organization, Central Fisheries Research Institute, Yoichi, Hokkaido 046-8555, Japan 2 Hokkaido National Fisheries Research Institute, Fisheries Research Agency, Katsurakoi, Kushiro, Hokkaido 085-0802, Japan † E-mail: sakaguchi-kenji@hro.or.jp A model to forecast the catches of the Japanese common squid, Todarodes pacificus, before the fishing season in the Sea of Okhotsk off Hokkaido was examined using information about the abundance of the squid in the Pacific off eastern Hokkaido and the sea surface temperature (SST) off Kunashiri Island, northeast of Hokkaido. Catches of the squid in the Sea of Okhotsk off Hokkaido by set nets during October to December, 1993 to 2011, with the exception of the outlier 1996 which was regarded as the response variable of the model were accurately predicted using a generalized linear model (GLM). Three explanatory variables used in the GLM were 1) catch per unit effort (CPUE) in the Pacific east off Kushiro in late August by research vessels, 2) CPUE of commercial jigging vessels at Kushiro Port during July to August and 3) SST in the southern area off Kunashiri Island in July. The correlation coefficient between the predicted catches by the model and the observed catches was 0.853. It is suggested that most of the squid caught in the Sea of Okhotsk off Hokkaido migrated from the Pacific Ocean rather than the Sea of Japan. Key words: Hokkaido, Okhotsk Sea, Japanese common squid, Todarodes pacificus, prediction, generalized linear model