东太湖鱼类群落结构特征及其与环境因子的关系

基于2019年4月、7月和10月的调查数据，用多元分析方法研究了围网拆除后东太湖鱼类群落结构的变化，及其与主要环境因子的关系。共调查到鱼类4目10科31属39种，其中鲤形目鱼类占69.23%。按不同生态类型东太湖鱼类主要为定居性鱼类、中上层鱼类以及肉食性和杂食性鱼类。优势种为鲫（Carassius auratus）、大鳍鱊（Acheilognathus macropterus）和（Hemiculter leucisculus）等。鱼类的种类数、渔获量、丰富度指数和多样性指数在监测月份间均差异显著（P＜0.05），均为4月 > 7月 > 10月。鱼类个体呈现小型化，鱼类物种多样性处在一般水平。等级聚类分析（Cluster）结果表明，除10月份的1号点和3号点外，各样方间的相似度在46.75%以上。单因子相似性分析（ANOSIM）和相似性百分比分析（SIMPER）也表明，4月和10月的鱼类群落物种组成差异显著，平均相异性为59.41%。丰度/生物量曲线（ABC）分析表明，东太湖鱼类群落结构处于中度干扰状态。冗余分析（RDA）表明，总磷对主要鱼类变化的解释量为21.0%，是重要的解释因子（蒙特卡罗检验P＝0.036）。而总磷、pH、溶解氧等是目前影响东太湖鱼类群落的主要环境因子。

Fish community structure and its relationship with main environmental variables in the East Taihu Lake

Lake aquaculture net-enclosure culture had been existing over the last 35 years in the East Taihu Lake, which brought a lot of water eco-environmental problems, while it was abolished completely in early April 2019. To provide a theoretical and scientific basis for the restoration, protection and management of fishery resources in the East Taihu Lake, the fish community structure and its relationship with the environment were studied by multivariate analysis using the data collected from the field surveys in late April, July and October, 2019. Variations on the spatio-temporal distribution patterns and community structure of fish community were determined by using Shannon-Wiener diversity index, Margalef''s species richness index, and Pielou''s evenness index. The relationships between abiotic environmental variables and fish community pattern were investigated with gradient analysis, combining Monte Carlo test to determine limiting factors affecting fish community structure. In total, 39 species were collected, belonging to 31 genera, 10 families, and 4 orders. Cypriniformes had the largest number of species, accounting for 69.23% of the total species captured. Sedentary fish species were the most frequent of the three ecological groups, and upper fish species were the most frequent of the three habitat types, whereas carnivore and omnivore fish species were the most frequent of the five feeding functional groups. Carassius auratus, Acheilognathus macropterus, and Hemiculter leucisculus were the dominant species. The mean values of species number, catch, species richness, Pielou''s evenness, and Shannon-Wiener index of fish community all showed significant differences in different months (P<0.05, April > July > October). Cluster analysis indicated that similarity was high (above 46.75%) in different months and stations, except station 1 and station 3 in October. ANOSIM (analysis of similarity) and SIMPER (similarity of percentage) analysis also revealed that the fish species composition in the East Taihu Lake varied significantly between April and October and the average dissimilarity was up to 59.41%. Abundance-biomass curves (ABC) of fish community indicated that the community was moderately disturbed. 21.0% of the variation in composition of fish community was explained by total phosphorus (TP) in the RDA analysis, which suggested TP was the main explanatory factor (Monte Carlo test P=0.036). At present, TP, pH and dissolved oxygen (DO) were key environmental variables for temporal variation of the fish community structure in the East Taihu Lake.