Effect of meso-scale oceanographic features on the larval growth and survival of small pelagic fishes in the Kuroshio-Oyashio transitional regions.

在本研究中，我们旨在探讨中尺度海洋学特征如何以及在多大程度上影响黑潮和黑潮-好潮过渡地区的小型远洋鱼类如凤尾鱼的幼虫生长和存活，黑潮和黑潮-好潮过渡地区是主要的产卵和育儿栖息地。为此，我们在对现有资料进行详细分析的基础上，对黑潮和黑潮扩展锋面扰动引起的中尺度涡旋进行了深入的野外调查。还建立了用于评价中尺度涡旋对生物生产与幼虫生长/存活关系的数值生物物理模型。研究表明，黑潮锋北缘与黑潮向北扩展有关的暖水区对鳀鱼和其他小型远洋鱼类的生物生产和幼虫生长/存活具有重要作用。特别是在这些区域由锋面扰动引起的中尺度涡旋，除了将小型幼虫带入涡旋边缘并积累外，还极大地提高了幼虫的食物产量。另一方面，在南部生产力较低的黑潮水域和北部与大潮水域相关的冷水中，幼虫的生长明显较低。因此，幼虫与中尺度涡旋相遇的可能性可以决定幼虫在近海水域的生存程度。

In this study, we aimed to explore how and to what extent meso-scale oceanographic features affect larval growth and survival of small pelagic fishes such as anchovy in the Kuroshio and Kuroshio-Oyashio transitional regions, where major spawning and nursery habitats were located. For this purpose, focusing on the meso-scale eddies caused by frontal disturbances of the Kuroshio and Kuroshio Extension, we made intensive field surveys in addition to detailed analyses of existing data. Numerical bio-physical models for evaluating the effect of meso-scale eddies on the biological production in relation to larval growth/survival were also developed.It has been revealed that warm water regions associated with the northward expansion of the Kuroshio water as seen in the northern edge of the Kuroshio front apparently play an important role in biological production and larval growth/survival of anchovy and other small pelagic fishes. In particular, meso-scale eddies caused by frontal disturbances in these regions contribute greatly to the enhancement of larval food production in addition to entraining and accumulating small-sized larvae into the edge of the eddies. On the other hand, larval growth is appreciably low in less productive Kuroshio water to the south and cold water associated with Oyashio water to the north. Therefore, possibility of the encounter of larvae with meso-scale eddies could determine the extent of larval survival in the offshore water.