Bull. Jpn. Soc. Fish. Oceanogr. 75(3), Page 154-160, 2011   Influence of Tsushima Warm Current on the fishing ground of jack mackerel (Trachurus japonicus) in the Sea of Genkai, Japan Akihiko Ando1†, Joji Ishizaka2 and Hideaki Nakata3 1 Graduate School of Science and Technology, Nagasaki University, 1-14 Bunkyo, Nagasaki, Nagasaki 852-8521, Japan 2 Hydrospheric Atmospheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan 3 Faculty of Fisheries, Nagasaki University, 1-14 Bunkyo, Nagasaki, Nagasaki 852-8521, Japan † a-ando@siren.ocn.ne.jp To examine the effect of the Tsushima Warm Current on the jack mackerel (Trachurus japonicus) fishery, we analyzed the operation record of this fish species by purse seine fishing boats and satellite sea surface temperature in May from 2000 to 2005. Distribution of the daily average fishing ground was determined by the average position compared with the weight of quantity of fished jack mackerel from the operation record. The distribution of the average fishing ground was classified roughly into two patterns: concentrated in the north east of Iki-Island or dispersed into north and south area. Position of the Tsushima Warm Current was also classified into the offshore and inshore patterns based on the monthly satellite sea surface temperature. In the years of the offshore pattern of the Tsushima Warm Current, the average fishing ground was dispersed. On the other hand, in the years of the inshore pattern, the average fishing ground was concentrated. These results indicated that inflow of the Tsushima Warm Current to the sea of Genkai has strong influence on the fishing ground formation of the jack mackerel. Key words: satellite, sea surface temperature, jack mackerel, Tsushima Warm Current, fishing ground