Fisheries Resource Research Institute, Japan Fisheries Research and Education Agency, Nagasaki, Japan.
Hakubi Center, Kyoto University, Yoshidanihonmatsucho, Kyoto Sakyo-ku, Kyoto, 606-8316, Japan.
Sci Rep. 2024 Sep 17;14(1):21722. doi: 10.1038/s41598-024-72925-8.
The abrupt decline in sardine catches in the Sea of Japan and the East China Sea (SJ-ECS) in 2014 and 2019 and the recovery in the following years call into question the current assumption that sardines in the SJ-ECS form a self-recruiting subpopulation. To test this hypothesis, we analysed otolith stable oxygen and carbon isotope profiles (δO, δC) of age-0 and age-1 sardines from 2010 and 2013-2015 year-classes captured in the SJ-ECS, as geographic markers for nursery areas. Age-0 sardines generally showed a significant ontogenetic decrease in otolith δO from larval to juvenile stages. However, the majority of age-1 captured in spring 2011, 2015 and 2016 showed non-decreasing otolith δO profiles, suggesting that the age-0 off the Japanese coast were not the main source of recruitment. Different migration groups were thus indicated: the "locals" growing up off the Japanese coast and the migrating "nonlocals". The isotope profiles of the "nonlocals" overlapped with those of age-0 captured in the subarctic North Pacific, suggesting that they may be migrants from the Pacific, or perhaps an unobserved northward migration group in the SJ-ECS. Our results highlight the considerable uncertainty in the population structure assumed in current stock assessment models for Japanese sardine.
2014 年和 2019 年，日本海和东海（SJ-ECS）的沙丁鱼捕捞量突然下降，随后几年又有所恢复，这对目前关于 SJ-ECS 沙丁鱼形成自我补充亚种群的假设提出了质疑。为了验证这一假设，我们分析了 2010 年和 2013-2015 年年龄为 0 龄和 1 龄的沙丁鱼耳石稳定氧和碳同位素剖面（δO、δC），这些沙丁鱼是在 SJ-ECS 捕获的，作为育苗区的地理标志。0 龄沙丁鱼的耳石 δO 通常从幼鱼到幼鱼阶段有显著的个体发育下降。然而，2011 年春季、2015 年和 2016 年捕获的大部分 1 龄沙丁鱼的耳石 δO 曲线并没有下降，这表明日本沿海的 0 龄沙丁鱼不是补充群体的主要来源。因此，不同的洄游群体被指出：在日本沿海长大的“本地人”和迁徙的“外地人”。“外地人”的同位素曲线与在北太平洋亚北极区捕获的 0 龄沙丁鱼的曲线重叠，这表明它们可能是来自太平洋的洄游鱼类，或者是 SJ-ECS 中未被观察到的向北洄游群体。我们的研究结果强调了目前日本沙丁鱼种群评估模型中对种群结构的假设存在相当大的不确定性。
