钱塘江西湖段鱼类群落结构特征

2016—2018年对钱塘江西湖段鱼类进行分季节采样调查，共采集到鱼类31种，隶属7目9科27属，其中鲤科（Cyprinidae）鱼类最多，有21种，占总物种数的67.74%；按生态类群划分则以淡水定居性、中下层、杂食性鱼类为主；优势种为鲫（Carassius auratus）、鲢（Hypophthalmichthys molitrix）、刀鲚（Coilia nasus）、鳙（Aristichthys nobilis）、窄体舌鳎（Cynoglossus gracilis）。与历史记录相比，鱼类资源衰退较为明显，仅江海洄游性鱼类及河口性鱼类就减少了16种，且存在资源小型化、物种单一化的问题。Jaccard相似性系数显示任意两年之间的鱼类物种组成均处于中等不相似水平，ABC曲线也显示2016和2018年鱼类群落较稳定而2017年处于受干扰状态。鲢、鲫和鳙为该江段目前最主要的鱼类资源，分别占渔获物总质量的49.65%、20.14%和16.19%，其中鲢和鳙完全依靠增殖放流补充。绝大多数钱塘江传统土著经济鱼类虽有长期增殖放流的补充，但未在该江段形成优势种群。鱼类多样性指数虽有一定的季节及年际波动，但其变化未达到显著水平，鱼类群落结构的季节变化则与鱼类自身生活习性及水域内水文地理特征均有一定程度的关系。建议对钱塘江河口段持续开展全面的鱼类群落及鱼类生境调查，为制定细化的鱼类保护措施提供科学依据。

Current situation of fish community structure in West Lake section of Qiantang River

The seasonal sampling was conducted in the West Lake section of Qiantang River from 2016 to 2018. A total of 31 species of fish belonging to 27 genera, 9 families and 7 orders were collected, among which the most species were Cyprinidae (21 species), accounting for 67.74% of the total species. According to ecological types, freshwater settlement, middle and lower layers, omnivorous fish are the main species. The dominant species were Carassius auratus, Hypophthalmichthys molitrix, Coilia nasus, Aristichthys nobilis, and Cynoglossus gracilis. Compared with the historical records, the decline of fish resources is more obvious, only the river and sea migratory fish and estuarine fish species decreased by 16 species, and there is the problem of fish miniaturization and singularity. The Jaccard similarity coefficient shows that the fish species composition is at a moderate dissimilarity level between any two years. The ABC curve also shows that the fish community was stable in 2016 and 2018, while it was disturbed in 2017.The Hypophthalmichthys molitrix, Carassius auratus and Hypophthalmichthys nobilis are the most important fish resources in this section, accounting for 49.65%, 20.14% and 16.19% of the total catch weight respectively.Although most of the traditional indigenous economic fishes in the Qiantang River are supplemented by long-term breeding and releasing, no dominant population has been formed in this section.Although the fish diversity index fluctuated seasonally and annually, the changes did not reach a significant level, and the seasonal changes of the fish community structure were related to the living habits of the fishes and the hydrogeological characteristics in the water to a certain extent.It is suggested to strengthen the protection of fish resources in this section of the river from the aspects of strengthening law enforcement, scientific breeding and releasing, improving habitat conditions and so on.In view of the lack of investigation into the fish community structure in the Qiantang River estuary section, it is suggested to carry out a comprehensive survey on the fish community and fish habitat in the Qiantang River estuary section continuously, so as to provide scientific basis for the formulation of detailed fish protection measures.