低头坝养鱼对上下游局域栖息地和鱼类群落时空格局的影响

河流鱼类的群落特征会随栖息地环境的变化而发生变化.为了解鱼类群落对低头坝养鱼的响应程度,2013—2014年共6次调查了乌龙河(长江下游支流)两个可涉水河段样点(上游坝和下游坝)的环境因子、鱼类多样性及其群落结构.共采集到5目10科21属24种鱼类,以鲤形目鲤科最多,占总数的58.3%.通过解析时空动态变化与局域栖息地条件对鱼类群落的影响,发现季节因素对鱼类群落结构无显著影响,而鱼类群落所在空间位置(上游坝,下游坝)对群落结构差异具有较显著影响,其中上游中华鳑鲏(Rhodeus sinensis)、(Hemiculter leucisculus)、棒花鱼(Abbottina rivularis)、大鳍鱊(Acheilognathus macropterus),下游食蚊鱼(Gambusia affinis)的多度决定了这种差异;而3个栖息地变量(溶解氧浓度、电导率和流速)均对鱼类群落特征具有显著性影响.栖息地环境差异对河流上、下游鱼类群落的影响较大,具体体现在下游样点鱼类的捕获重量、捕获数量、密度、多样性明显下降,推测利用低头坝养鱼是造成这些现象的重要原因.

Low-head-dam fish culture effects on spatial-temporal patterns of local habitat and fish assemblages in the upstream and downstream of rivers

Fish assemblage will change along with the river habitat environment. In order to find the response degree of fish assemblage to fish culture within low-head-dam water, two low-head dams (including the upstream and downstream dams) of the Wulong River (a tributary of the lower reach of the Yangtze River, China) were selected as sampling sites, where the habitat variables, the fish diversity and fish assemblage structure were surveyed for 6 times from 2013 to 2014 in these wadeable reaches of the sampling sites. A total of 24 fish species which belong to 5 orders, 21 genera and 24 species were caught, with dominant Cyprinidae accounting for 58.3% of the total. After an analysis on the influences of temporal changes and local habitat conditions upon the fish assemblage, seasonal factors were found to have no apparent effect on the fish assemblage structure. The spatial location (the upstream dam or the downstream dam) affected the assemblage''s structural differences significantly, which were determined by the abundance of Hemiculter leucisculus, Abbottina rivularis, Rhodeus sinensis, Acheilognathus macropterus in the upstream site, and the abundance of Gambusia affinis in downstream site. Besides, all the three habitat variables including dissolved oxygen, conductivity and current velocity exerted a great impact on the fish assemblage. The differences in habitat environment bring about some great influences on the fish assemblage, showing in the dramatic decrease of capture weight, quantity, density and diversity of fish in the sampling sites of the downstream dam, which are probably caused by the fish culture within the low-head dam.