[A-OS09] Marine ecosystems and biogeochemical cycles: theory, observation and modeling

[AOS09-15] A scheme to reproduce migration history of the Japanese sardine; combination use of otolith d¹⁸O and an individual-based migration model

*Tatsuya Sakamoto¹, Kosei Komatsu^2,1, Shirai Kotaro¹, Tomihiko Higuchi¹, Toyoho Ishimura³, Takashi Setou⁴, Yasuhiro Kamimura⁴, Chikako Watanabe⁴, Atsushi Kawabata⁵ (1.Atomsphere and Ocean Research Institute, The University of Tokyo, 2.Graduate School of Frontier Sciences, The University of Tokyo, 3.National Institute of Technology, Ibaraki College, 4.National Research Institute of Fisheries Science, 5.Fisheries Agency)

Keywords:sardine, otolith, individual-based model, data assimilation model

Tracking the movement of migratory fish are of great importance in fisheries science, although it has been technically difficult for small sized fish to which artificial tags cannot be attached. Oxygen stable isotope ratio (δ¹⁸O) in otolith is known to record the linear combination of temperature and salinity variation of ambient water, and thus considered to be a potential alternative for conventional techniques such as tagging and electronic loggers. However, the difficulty of separating the two factors have been limiting its application. In this study, we show that the migration history of small pelagic fish, the Japanese sardine, can be individually reproduced by the combination use isotopic analysis and numerical migration simulations. We found that the detailed and reasonable movements can be estimated by searching the routes that should be passed to reproduce the otolith δ¹⁸O history, using a simple individual based migration model in a realistically simulated ocean. The scheme will enable researchers to estimate the environment that an individual fish experienced in the early life history for numerous species, which will improve the understanding of how the survival of fish is affected by environmental variabilities.