Kuroki Mari, Hayasaka Shunsuke, Nishida Kozue, Ishimura Toyoho, Okamura Akihiro, Yamada Yoshiaki, Han Yu-San, Shirai Kotaro
Graduate School of Agriculture and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657, Japan.
Interfaculty Initiative in Information Studies, The University of Tokyo, Hongo, Bunkyo, 113-0033, Tokyo, Japan.
Sci Rep. 2025 Jan 10;15(1):1584. doi: 10.1038/s41598-025-85523-z.
Migration routes and the depth patterns of anguillid eel larvae migrating long distances from spawning grounds in the ocean remain poorly understood. We used otolith stable isotope analysis to study the oceanic migrations of anguillid eels by reconstructing experienced water temperature histories of larvae. The otolith stable oxygen isotopes (δO) of recruited Anguilla japonica glass eels were analyzed to assess the relationship with the experienced water temperature of the early larval stage in laboratory experiments. A negative linear relationship between rearing water temperature and δO values was observed for eel leptocephali reared at five different temperatures between 19 °C and 27 °C. Subsequently, the obtained equation between water temperature and δO was applied to estimate the water temperature experienced by wild-caught glass eels during their larval oceanic migration according to recruitment latitude, season, and species. The δO values of A. japonica glass eels were significantly higher at higher recruitment latitudes from Taiwan to Japan and later recruitment periods of 6 months, from November to March, indicating that the individuals were exposed to lower water temperatures along the Kuroshio flowing northward as they reached the higher latitudes in the later recruitment seasons. Furthermore, the δO values of the temperate A. japonica were higher than those of the tropical Anguilla marmorata, recruited at the same locations in southern Japan and Taiwan. This suggests that larval migratory behavior in the ocean may differ between the two eel species, although they have sympatric spawning areas in the western North Pacific. Collectively, these results suggest that δO provides a reasonable estimation of the experienced water temperature and may prove useful for reconstructing the early migratory history of anguillid eels in the ocean.
鳗鲡幼体从海洋产卵地远距离洄游的路线及深度模式仍知之甚少。我们利用耳石稳定同位素分析，通过重建幼体经历的水温历史来研究鳗鲡的海洋洄游。在实验室实验中，分析了新采集的日本鳗鲡玻璃鳗的耳石稳定氧同位素（δO），以评估其与幼体早期经历水温的关系。在19℃至27℃的五个不同温度下饲养的鳗鲡柳叶鳗，其饲养水温与δO值之间呈现负线性关系。随后，根据采集纬度、季节和物种，将所获得的水温与δO之间的方程应用于估算野生捕获的玻璃鳗在幼体海洋洄游期间经历的水温。从台湾到日本，随着采集纬度升高以及11月至次年3月这6个月较晚的采集期，日本鳗鲡玻璃鳗的δO值显著更高，这表明个体在较晚的采集季节到达较高纬度时，沿着向北流动的黑潮接触到了更低的水温。此外，在日本南部和台湾相同地点采集的温带日本鳗鲡的δO值高于热带花鳗鲡。这表明，尽管这两种鳗鲡在北太平洋西部有同域产卵区，但它们在海洋中的幼体洄游行为可能存在差异。总体而言，这些结果表明δO能够合理估算经历的水温，可能有助于重建鳗鲡在海洋中的早期洄游历史。
