黄海大头鳕食性随体长及季节的变化

根据2017—2021年在黄海海域捕获的大头鳕（Gadus macrocephalus）样品，进行体长、体质量等生物学测量和胃含物鉴定，并用分类树方法对489个胃含物数据进行分析，探究其食性随季节及体长的变化特性。结果显示：从相对重要性指数百分比来看，2017—2021年大头鳕饵料中脊腹褐虾（Crangon affinis）及鳀（Engraulis japonicus）相对较高，其次为方氏云鳚（Enedrias fangi）、日本鼓虾（Alpheus japonicus）、虾虎鱼等；食性随季节变化较大，夏秋季节主要捕食脊腹褐虾和鳀，而春冬季食性相对广泛、香农-威纳指数比较高，捕食饵料种类相对较多，这可能与春冬季节大多数渔业种类在黄海越冬场越冬有关；大头鳕食性随体长增长发生变化，幼鱼主要捕食甲壳类动物，成鱼转变到摄食虾虎鱼、方氏云鳚等鱼类，这主要与大头鳕随自身生长，口裂不断变大，游泳能力变强，自身生长所需要的营养物质增多有关；胃含物中发现了其他大头鳕个体，表明其存在同类相食现象。此外与之前研究相比，大头鳕饵料丰富度逐渐下降，太平洋磷虾（Euphausia pacifica）、小黄鱼（La...

Seasonal and ontogenetic changes in the diet of Pacific cod (Gadus macrocephalus)

In this paper, biological measurements such as body length and body weight and identification of stomach contents were carried out based on Pacific cod(Gadus macrocephalus)samples captured in the Yellow Sea during 2017 to 2021. Decision tree method was used to analyze 489 stomach contents data to explore the changes of feeding habits with body length and seasons. The results showed that the relative importance index of Crangon affinis and Engraulis japonicus was relatively high in 2017-2021, and the next were Enedrias fangi, Alpheus japonicus and Gobiidae. Its feeding habits vary greatly with seasons, mainly preying on Crangon affinis and Engraulis japonicus in summer and autumn, while its feeding habits are relatively wide and its Shannon-Wiener index is higher in spring and winter, which may be related to the overwintering of most fishery species in the Yellow Sea during spring and winter. In addition, the Pacific cod "s feeding habits change with the growth of its body length. The juveniles mainly feed on crustaceans, while the adults shift to eat Gobiidae, Enedrias fangi, etc. The main reason is that the Pacific cod "s mouth cleave becomes larger, its swimming ability becomes stronger, and it has more nutrients to meet the growth requirements. Other Pacific cod individuals were found in the gastric contents, indicating cannibalism. In addition, compared with previous studies, the diet abundance of prey gradually decreased, Euphausia pacifica and Larimichthys polyactis almost did not appear in the stomach, and the importance of Engraulis japonicus gradually decreased, and Gobiidae are becoming more important.