长江口青草沙水库正式供水前的鱼类群落结构特征

Structure of fish assemblages before drinking-water supplies in Qingcaosha Reservoir of Yangtze River Estuary

为研究上海青草沙水库的鱼类物种组成、多样性及其空间变化,2010年7—10月在该水库共捕获鱼类993尾,隶属5目,18种,其中淡水鲤形目鱼类最多,占总物种数的72.2%。群落优势种为贝氏、刀鲚、鲫、光泽黄颡鱼。聚类分析表明,鱼类群落类型存在较显著的空间差异,刺网网目大小对渔获物物种组成有较显著的影响。物种多样性与丰富度和均匀度均显著正相关,但更多地受丰富度的影响。单因素方差分析表明,鱼类物种多样性在空间上无显著差异。4种摄食功能群中,无脊椎动物食性(44.4%)和杂食性(33.3%)鱼类物种数比例较高;4种生态类群中,定居性鱼类占绝对优势(77.8%)。青草沙水库鱼类群落表现出淡水或长江口低盐淡水区鱼类区系的主要特征,与以近海鲈形目鱼类为优势的长江口邻近水域的鱼类群落差异巨大,推测水库建设导致的隔离与盐度下降是形成该水库鱼类群落趋于淡水区系的主要原因。

In order to provide basic data for the oncoming bio-manipulation based on fish and reference system for hereafter investigating its subsequent effect on fish composition in a newly established water supply reservoir （Qingcaosha Reservoir in Shanghai of China）, fish assemblages in this reservoir were sampled by multimesh gillnets from Jul. to Oct. in 2010. A total of 993 individuals, belonging to 18 species, representatives of 5 orders, were caught, of which Cypriniformes accounted for 72.2% of the total species number. Based on importance value, Hemiculter bleekeri, Coilia nasus, Carassius auratus and Pseudoba- grus nitidus were the dominant species. Clustering analysis （CA） showed that fish assemblages signifi- cantly differed spatially, and there were marked effects of net size on species composition of fish catch. One-way ANOVA indicated that there were no significant spatial differences in fish diversities. Although Shannon＇s species diverisity （H＇） was conspicuously positively correlated with Margalef＇s species richness （R） and evenness （J）, respectively, H＇ was governed more by R. Invertivorous （44.4%） and omnivorous （33.3%） fishes prevailed in species number among the 4 feeding functional groups, and sedentary fishes （77.8%） predominated among the 4 ecological groups. Contrasting to the adjacent estuarine zone with more species of Perciformes and dominated by estuarine and/or inshore fishes, Qingcaosha Reservoir was characterized by dominance of freshwater or low salinity water fishes. It is presumed that isolation and decreased salinity that resulted from reservoir construction would be responsible for the fish characteristics of Qingcaosha Reservoir.