The Pacific bluefin tuna Thunnus orientalis is a highly migratory species, some tuna exhibiting a trans-Pacific migration between the Western Pacific Ocean (WPO) to the Eastern Pacific Ocean (EPO) at the juvenile stage. To detect a signature for the eastward trans-Pacific migration, we analyzed otolith stable isotope ratios of carbon (δ13Coto) and oxygen (δ18Ooto) along the growth trajectory for 20 migrants (age 3–5 years) from the EPO and 10 residents (age 2–3 years) from the WPO. The δ18Ooto values for migrants recorded during the eastward trans-Pacific migration were higher than those for residents during the same period. The higher δ18Ooto values for migrants reflect the low water temperatures encountered during their migration. The δ13Coto values were higher in the migrants than in the residents, suggesting that the higher values of carbon isotope ratios of both dissolved inorganic carbon and the diet in the EPO are recorded in the δ13Coto profiles. Our study demonstrates that otolith isotope analyses can successfully detect trans-Pacific migration of the Pacific bluefin tuna.

中文翻译：

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通过耳石δ13C和δ18O分析鉴别太平洋蓝鳍金枪鱼Thunnus orientalis向东跨太平洋迁移

太平洋蓝鳍金枪鱼 Thunnus orientalis 是一种高度洄游的物种，一些金枪鱼在幼年阶段表现出从西太平洋 (WPO) 到东太平洋 (EPO) 的跨太平洋迁徙。为了检测跨太平洋向东迁移的特征，我们分析了来自 EPO 的 20 名移民（3-5 岁）和 10 名居民（年龄2-3 年）来自 WPO。在向东跨太平洋迁移期间记录的迁移者的 δ18Ooto 值高于同期居民的δ18Ooto 值。迁移者较高的 δ18Ooto 值反映了迁移过程中遇到的低水温。流动人口的δ13Coto 值高于居民，表明在 δ13Coto 剖面中记录了 EPO 中溶解无机碳和饮食的碳同位素比值的较高值。我们的研究表明，耳石同位素分析可以成功检测太平洋蓝鳍金枪鱼的跨太平洋迁移。