长江近口段近岸段鱼类群落多样性现状

为掌握长江近口段近岸鱼类群落多样性现状，于2017年在南通和常熟江段开展了鱼类周年调查，统计分析了主要群落参数及时空特征。结果显示，本次调查共采集到鱼类62种，隶属于8目16科49属，优势类群为淡水定居性鱼类(物种数及渔获尾数占比分别为70.97%、14.52%)、杂食性鱼类(占比分别为53.22%、71.01%)和底层鱼类(占比分别为46.77%、17.92%)，渔获规格上以均重小于50 g的小型鱼类及幼鱼占优势，物种数及尾数占比分别为59.68%和37.59%。Margalef指数(D)、Shannon-Wiener指数(H′)、Simpson指数(C)和Pielou指数(J′)的变幅分别为0.97~6.32、1.15~2.92、0.00~0.33和0.72~1.00，就群落多样性水平而言，时间特征表现为春夏季高于秋冬季，空间特征则表现为常熟采样点高于南通采样点。长江近口段近岸渔获尾数同样呈现出季节性差异，夏季的渔获尾数最高，冬季最低。聚类结果表明鱼类群落在相似度44.34%时被划分为2个类群，群落差异更多的来自于季节变化。

Species diversity of fish in the section near the Yangtze River estuary

In order to understand the fish community structure and diversity in the section near the Yangtse River estuary. The temporal and spatial characteristics of fish community structure, dominant species, quantity and biomass were investigated in 2017. The results showed that 62 species of fishes were collected, belonging to 8 orders, 17 families. In terms of the ecological types, omnivore fish, sedentary fish and demersal fish were dominant. In terms of fish catching specifications, small-sized fishes (<50 g) were dominant in quantity and species (67.79% and 37), and quantity of fishes with average mass less than 50 g was 59.68% and 37.59%.Analysis of the diversity index showed that the range of Margalef index(D) was 3.73 to 6.26, Shannon-Wiener index(H'') was 2.44 to 2.98, Simpson index(C) was 0.07 to 0.15 and Pielou index(E) was 0.64 to 0.76, and the average value of them was 5.03,2.62,0.12 and 0.73. As a whole, the community diversity index in spring and summer was higher than that in autumn and winter; that community diversity index in Changshu sampling site was higher than that in Nantong sampling site. Significant seasonal variations showed that fish quantity was highest in summer and lowest in winter. The clustering results showed that the fish community was divided into 2 groups when the similarity was 44.34%. Community differences are mainly due to the seasonal variation. The research supplemented the basic data of fish and provided a scientific basis for the assessment and protection of fishery resources in Yangtze River basin.