Bull. Jpn. Soc. Fish. Oceanogr. 84(3), Page 149-160, 2020   Characteristics of spatiotemporal distribution of small blackthroat seaperch Doederleinia berycoides in the southwestern Japan Sea and model development for predicting the distribution Yasuyuki Kanamoto1a,Takuya Takazawa2,Hisae Miyahara3,Atsushi Michine4,Akira Okino1, Hiroyoshi Terakado1,Tatsuro Murayama5 and Minoru Kanaiwa6 1 Fisheries Productivity Division, Shimane Prefectural Fisheries Technology Center, Hamada, Shimane 697–0051, Japan aPresent: Inland Water Fisheries and Coastal Fisheries Division, Shimane Prefectural Fisheries Technology Center, Matsue, Shimane 690–0322, Japan 2Taiki Town Hall, Taiki, Mie 519–2703, Japan 3Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Niigata, Niigata 951–8121, Japan 4Shimane Prefectural Hamada Regional Office of Fisheries Affairs, Hamada, Shimane 697–0041, Japan 5Ltd. Hamada Akebono Suisan, Hamada, Shimane 697–0017, Japan 6Graduate School of Bioresources, Mie University, Tsu, Mie 514–8507, Japan An offshore trawl fishery within Shimane Prefecture in Japan has introduced mobile protected areas using information from fisheries to manage the resources of the small blackthroat seaperch Doederleinia berycoides since 2012. However, there is an increasing need to understand the distribution of these fish within the entire sea area in advance and to set up efficient protected areas using this information. In this study, we used a random forest method to develop a model for predicting the distribution of these fish in the southwestern Japan Sea using the operating information of the offshore trawl fishery from March to May of 2011–2018 and estimated values of bottom water temperature, salinity, and tidal current. The prediction error against out-of-bag(OOB)data for a model developed in the year of operation was 14.5% and that developed using CPUE in the first half of the fishing year was 14.6%. In addition, the prediction accuracy for test operations by a research vessel was 94%. Based on these results, we elucidated the spatiotemporal distribution of this fish and discussed the characteristics of factors affecting the distribution. Key words: blackthroat seaperch, random forest, prediction of spatiotemporal distribution, offshore trawl fishery, southwestern Japan Sea