Bull. Jpn. Soc. Fish. Oceanogr. 84(3), Page 187-199, 2020   Estimation of artificial reef effect range in the waters of Tsushima Islands, Nagasaki, Japan ariaki Inoue1†,Hisami Kuwahara1,Ryogen Nambu2,Satoshi Ishimaru3,Kengo Hashimoto3,Junji Kuwamoto3,Takahito Masubuchi4 and Minoru Kanaiwa4 1 National Research Institute of Fisheries Engineering, Japan Fisheries Research and Education Agency, 7620–7 Hasaki, Kamisu, Ibaraki 317–0408, Japan 2 Japan International Research Center for Agricultural Sciences, 1–1 Ohwashi, Tsukuba, Ibaraki 305–8686, Japan 3 Nagasaki Branch, Fisheries Infrastructure Development Center, 17–1 Motofuna-machi, Nagasaki-shi, Nagasaki 850–0035, Japan 4 Mie University, 1577 Kurimamachiya-cho, Tsu, Mie 514–8507, Japan † E-mail: nariaki23@affrc.go.jp Most studies on the effects of artificial reefs (AR) have used fishery-independent research data, and very few have utilized actual commercial fisheries data sets (fishery-dependent data). Commercial fisheries catches and nominal catch per unit effort (CPUE), which is calculated by dividing catch by effort, are considerably impacted by many factors, including the AR effect, the fishing area, the ship’s capacity, and annual and seasonal resource fluctuations. If nominal CPUE data are used for analysis, the independent effects of an AR on resources density cannot be accurately estimated. To overcome the above difficulties, we applied standardized CPUE methods and estimated the spatial range of AR effects for three species (Hyperoglyphe japonica, Seriola lalandi, and Parapristipoma trilineatum). For H. japonica, the resource density near ARs was seven times higher than that in natural reef areas, with effects ranging up to <350 m from the AR center. For S. lalandi, typical effects ranged up to <100 m from the AR center; however, the effect of AR on P. trilineatum was limited to the immediate AR area. Key words: artificial reef, Tsushima Islands, CPUE Standardization, resource density, effect range