Bull. Jpn. Soc. Fish. Oceanogr. 79(3), Page 141-148, 2015   Change in drift-fishing activities due to the introduction of a tidal current calendar in a coastal area off Cape Soya in Hokkaido, Japan Minoru Sano1†, Tadao Bando2, Shinichi Motomae3 and Naoto Ebuchi3 1 Wakkanai Fisheries Research Institute, Hokkaido Research Organization, Wakkanai, Hokkaido 097-0001, Japan 2 Soya Fisheries Cooperative Association, Wakkanai, Hokkaido 098-6755, Japan 3 Nemuro Fisheries Extension Office, Shibetsu, Hokkaido 086-1364, Japan 4 Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819, Japan † E-mail: sano-minoru@hro.or.jp A tidal current calendar for the coastal area off Cape Soya in Hokkaido, Japan, has been used by fishermen of the drift fishery for giant Pacific octopus, Enteroctopus dofleini, since 2009. In the present study, the accuracy of suitable surface current velocities described in the calendar was verified and changes in drift-fishing activities resulting from the introduction of the calendar were clarified. A regression tree analysis of surface velocity measurements recorded by high-frequency ocean radar stations in the Soya region and the catch (kg·boat−1·day−1) showed that the catch increased when the surface velocity was in the range of 0.1 to 1.0 kt. Surface velocities were simulated based on tidal currents and the mean velocity of the Soya Warm Current. A correlation coefficient of 0.79 was obtained between the observed velocity and the simulated velocity. After the introduction of the calendar, the proportion of actual fishing days to possible fishing days (Fishing Effort Index) for fishermen who fished ≥50 days per year decreased. Most fishermen did not go fishing on days considered unsuitable for drift fishing after the introduction of the calendar. Key words: drift fishery, Enteroctopus dofleini, HF radar, Soya/La Pérouse Strait, surface current, tidal current calendar