[Feeding ecology of Decapterus maruadsi in the southern coastal area of Zhejiang based on stomach contents and stable isotope analysis.]

Decapterus maruadsi is an important economic pelagic fish in the southern coastal area of Zhejiang. According to the bottom trawl surveys conducted in May, August, November 2020 and January 2021, the feeding habits of D. maruadsi in the southern coastal area of Zhejiang were examined by both stable isotope (carbon, δ13C, and nitrogen, δ15N) and stomach content analyses. Results showed that the δ13C value of D. maruadsi ranged from -17.76‰ to -15.25‰, with a mean of (-16.55±0.60)‰, while the δ15N value ranged from 9.06‰ and 13.03‰, with a mean of (11.76±0.88)‰. There was a significant negative correlation between the δ13C values and fork length, and a positive relationship between the δ15N with fork length. Results from stomach content analysis showed that the main prey groups of D. maruadsi were fish, shrimp, crabs, Cephalopod, Polychaete, and small crustaceans. As for the stable isotope analysis, the nutritional contribution rate of shrimp was the highest (40%-84%) among all prey groups, followed by Polychaete, small crustaceans, crabs, Cephalopods and fish. Significant ontogenetic dietary changes were found for D. maruadsi. As the fork length of D. maruadsi increased, it tended to eat prey from higher trophic levels.蓝圆鲹是浙江南部近海的重要经济鱼类。本文根据2020年5月、8月、11月和2021年1月在浙江南部近海进行的底拖网调查,应用胃含物分析和碳氮稳定同位素分析对浙江南部近海蓝圆鲹的摄食习性进行研究。结果表明: 浙江南部近海蓝圆鲹δ13C平均值为(-16.55±0.60)‰,范围为-17.76‰～-15.25‰,与叉长呈显著负相关;蓝圆鲹δ15N平均值为(11.76±0.88)‰,范围为9.06‰～13.03‰,与叉长呈显著正相关。根据δ15N值计算浙江南部近海蓝圆鲹的平均营养级为3.89±0.26。胃含物分析表明,浙江南部近海蓝圆鲹的主要饵料类群为鱼类、虾类、蟹类、头足类、多毛类和小型甲壳类。稳定同位素分析表明,虾类对浙江南部近海蓝圆鲹的营养贡献率最高(40%～84%),其次为多毛类、小型甲壳类、蟹类、头足类和鱼类。蓝圆鲹的摄食习性有明显的生长变化,随着蓝圆鲹叉长的增加,其倾向于摄食更高营养级的饵料生物。.