Abstract：
The influences of oceanographic changes on diet composition and trophic level for pollock (Gadus chalcogrammus) inhabiting the East Sea off the Korean coast were examined based on stomach content and stable isotope analyses during 2016 and 2017. The diets of pollock consisted mainly of benthic crustaceans (particularly carid shrimps and euphausiids) and cephalopods, with a predominance of teleosts in the diets of larger individuals in deeper habitats. In 2016, amphipods, carid shrimps and cephalopods featured strongly in pollock diets, and the contribution of amphipods decreased in the diets of larger individuals and deeper depths. In 2017, euphausiids dominated at shallower depths, whereas the contributions of carid shrimps and teleosts increased in deeper habitats. Body-size-related differences in carbon stable isotope (δ13C) values were present in both 2016 and 2017, but size-related differences in nitrogen stable isotope (δ15N) values were only observed in 2017. The increased contribution of euphausiids during 2017 resulted in a distinct decrease in the trophic level of pollock compared to co-occurring higher trophic level predators, which can be linked to changes in habitat water temperature. Combined stomach contents and isotopic analyses provide a more comprehensive understanding of how fish diets and trophic levels fluctuate with changes in the type and abundance of prey resources in response to environmental changes.
摘要：
根据2016年和2017年的胃含量和稳定同位素分析，研究了海洋学变化对居住在朝鲜沿海东海的鳕鱼（Gaduschalogrammus）的饮食组成和营养水平的影响。鳕鱼的饮食主要包括底栖甲壳类动物（尤其是卡利虾和euphausiids）和头足类动物，在较深的栖息地中，较大个体的饮食中以硬骨鱼为主。2016年，两栖动物，carid虾和头足类动物在鳕鱼饮食中表现突出，在较大个体和较深深度的饮食中，两栖动物的贡献减少。2017年，euphausiids在较浅的深度占主导地位，而在较深的栖息地，carid虾和硬骨鱼的贡献增加。2016年和2017年都存在与体型相关的碳稳定同位素（δ13C）值差异，但仅在2017年观察到与尺寸相关的氮稳定同位素（δ15N）值差异。与共同发生的较高营养级食肉动物相比，2017年euphausiids的贡献增加导致pollock的营养级明显下降，这可能与栖息地水温的变化有关。结合胃内容物和同位素分析，可以更全面地了解鱼类饮食和营养水平如何随着猎物资源类型和丰度的变化而波动，以响应环境变化。
