为了解长江口鱼类群落粒径结构特征及群落稳定性状态，实验基于2018年长江口四季鱼类资源与环境调查数据，利用标准化粒径谱、群落稳定性评估模型对鱼类群落特征进行了探究，并利用营养指数法对长江口水体生态环境质量状况进行了综合评价。结果显示：①长江口鱼类粒级主要分布在?2~6范围内，曲线穹顶位于0~3粒级范围，鱼类群落以小型鱼类为主，整体处于受干扰状态；②北支和南支的鱼类群落存在季节变化，北支粒径谱曲率夏季最大(–0.04)，秋季最小(–0.41)，生物量与数量相对关系统计量W值为–0.11~0.12；南支粒径谱曲率夏季最大(–0.04)，冬季最小(–0.24)，W值为–0.03~0.37；③南支鱼类群落稳定性系数均值为0.57，北支均值为0.43，4个季节南支与北支鱼类群落稳定性程度不同。水质营养指数表明，北支富营养化程度(18.89)较南支(5.43)高，且富营养化指数和群落稳定性系数呈显著负相关，水体富营养化或对长江口鱼类群落系统偏离稳定状态有重要影响。研究表明，长江口鱼类群落粒径偏小，鱼类群落稳定性不高，水质呈富营养化状态。本研究探究了全面禁捕前长江口鱼类粒径结构特征并评估了鱼类群落稳定性，为长江口禁渔效果评价提供了前期研究依据。

The Yangtze River estuary is the largest estuary ecosystem in China. It has sufficient nutrients and provides necessary habitat, bait and breeding grounds for different ecological types of fish. With the advancement of the policy “Yangtze River Great Protection”, the key waters of the Yangtze River basin have entered a ten-year fishing ban. From the perspective of scientific research, evaluating the effects of fishing bans is an important research task and carrying out such research has an essential ecological significance for fisheries protection and recovery in the Yangtze River estuary. Based on the fishery and environmental survey data in the four seasons in 2018, the size structure characteristics and community stability were studied using the normalized fish size spectrum and stability assessment model to improve the understanding of fish community in the Yangtze River estuary. Meanwhile，the water quality of the Yangtze River estuary was evaluated using the eutrophication index method. The results showed the following. ① The size classes ranged from ?2 to 6, and all the dome of all fish size spectrum curves located in the size class of 0 and 3, indicating that the fish community was dominated by small fishes and was in a disturbed state. ② There were seasonal changes in fish communities of the North Branch and the South Branch, with the maximum fish size spectral curvature in summer (?0.04) and the minimum in autumn (?0.41) and W values of ?0.11 to 0.12 in the North Branch, and the maximum fish size spectral curvature in summer (?0.04) and the minimum in winter (?0.24) and W values of ?0.03 to 0.37 in the South Branch. ③ The average stability factor of South Branch was 0.57, while it was 0.43 in the Northern Branch, which indicated that the stability of the fish community was different in four seasons. The eutrophic coefficient indicated that the eutrophication levels of the North Branch (18.89) was higher than that of the South Branch (5.43), and there was a significant negative correlation between the eutrophication index and the stability factor, which indicated that eutrophication may have an important influence on the deviation of the community system from the stable state. In general, the size class of the fish community is small, the community stability is weak, and the water quality is eutrophic in the Yangtze River estuary. This study explored the characteristics of fish community size structure and evaluated its community stability in the Yangtze River estuary before the implement of the fishing ban in the Yangtze River basin, thus providing a preliminary research for evaluating the effect of the fishing ban on the Yangtze River estuary ecosystem.

S 931.2

国家自然科学基金(41606146)；上海市科委高校地方能力建设项目(21010502200)