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

[AOS09-15] 耳石酸素安定同位体比分析と個体ベースモデルを用いたマイワシの回遊履歴推定法

*坂本 達也¹、小松 幸生^2,1、白井 厚太朗¹、樋口 富彦¹、石村 豊穂³、瀬藤 聡⁴、上村 泰洋⁴、渡邊 千夏子⁴、川端 淳⁵ (1.東京大学大気海洋研究所、2.東京大学大学院新領域創成科学研究科、3.茨城工業高等専門学校、4.水産研究・教育機構中央水産研究所、5.水産庁)

キーワード：マイワシ、耳石、個体ベースモデル、同化モデル

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.