Bull. Jpn. Soc. Fish. Oceanogr. 85(1), Page 1-13, 2021   BGeochemical analysis of otoliths to study the migratory ecology of tunas Yosuke Amano1,†, Kazuki Yokouchi2, Toyoho Ishimura3,a and Kotaro Shirai4 1 Fukushima Prefectural Fisheries and Marine Science Research Centre, Onahama, Iwaki, Fukushima 971�8101, Japan 2 National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Kanagawa 236�8648, Japan 3 National Institute of Technology, Ibaraki College, Nakane, Hitachinaka, Ibaraki 312�8508, Japan 4 International Coastal Research Center, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277�8564, Japan a Present: Graduate School of Human and Environmental Studies, Kyoto University, Sakyo, Kyoto, Kyoto 606�8501, Japan † E-mail: amano.ynwa@gmail.com Tunas, which are known for their large-scale migration around the world, are a commercially important international fishery resource. Thus, it is essential to establish appropriate management policy to maintain stock biomass at an appropriate level. For this purpose, detailed knowledge on migratory ecology is indispensable, but it is often difficult to investigate the ecology of tunas that migrate widely in the open ocean. This paper reviews ecological research of tunas using trace element and stable isotopic compositions of otoliths as a natural tag, which serve as a technique to complement conventional migratory ecological research. This paper outlines how otoliths as natural tags can play an important role for ecological research of tunas in the future. Key words: tunas, migration and ecology, otolith, stable isotope, trace element