三峡库尾江段鱼类行为节律研究

As the largest reservoir in China, the water environment and flow regime in the Three Gorge Reservoir (TGR) has been changed dramatically after impoundment of the reservoir. Patterns of fish biodiversity were reconstructed in the man-made reservoir ecosystem. A number of studies have indicated that fish stock and the diversity of fish community in reservoir depended on the fish recruitment from the upper reaches. As an ecotone between the river upstream and the lacustrine zones of the reservoir, the backwaters hold a high density of fishes. Fish movement between lacustrine zones and river sections upstream plays a crucial role in maintaining fish population dynamics and their diversity in reservoir. Under this background, it is urgent to understand the behavioral rhythms and ecological processes of fish in the backwaters of TGR. In this project, we will employ the mobile and fixed location split-beam horizontal echosoundings to monitor the movements of fish in Mudong reach. Combined with the fish catches, we aim to figure out the main species and its population size which moved up and down through the backwater for communications. Then, the influence of selected environmental variables, such as water temperature and discharge, on the movement of fish will be analyzed. Furtherly, we will evaluate the potential impact of reservoir operation on fish movements. These results can provide the scientific basis for making an optimal reservoir operation scheme to meet the goal of ecological sustainability.

三峡水库是我国最大的河道型水库，蓄水后库区的水文、水环境发生了极大的变化，鱼类多样性格局发生重构，水库型生态系统逐渐形成。研究表明，库区鱼类资源的丰度和群落多样性的形成依赖于上游河流区的补充过程。水库库尾江段作为上游河流区和下游湖泊区的过渡区域，鱼类多样性较高，同时也是上下游鱼类交流重要的生态通道，对于维持库区鱼类多样性的生态功能意义重大。本研究拟选取三峡库尾木洞江段为研究区域，运用水声学、渔获物调查等方法对鱼类行为交流的时空特征进行研究，分析鱼类在不同时间尺度（季节和昼夜）的行为节律以及鱼类对不同水域（或空间）的选择行为；对经过库尾生态通道进行上下交流的主要种类及其资源量进行调查；建立鱼类行为节律与水生态因子之间的对应关系，找出影响鱼类行为的关键因子；进一步模拟三峡水库运行调度对鱼类行为的影响，探索兼顾鱼类多样性保护与保证水利工程自身效益的生态调度模式。

生态交错区往往具有较高的生物多样性。三峡库尾江段作为连接上游“长江上游珍稀、特有鱼类国家级自然保护区”和下游水库淹没区的过渡地带，生态功能十分重要。本项目综合运用水声学探测、渔获物调查、早期资源调查和定点捕捞等多种方法，从三峡库尾木洞江段的鱼类多样性及群落结构、鱼类资源的时空分布特征、鱼类上下行的昼夜节律以及鱼类对微生境的选择等方面开展研究。结果表明，1）木洞江段共采集鱼类91种，隶属于6目15科。其中长江上游特有鱼类17种，外来种7种。群落结构方面，圆筒吻鮈是该江段的优势种，占总重量的50.4%，占总尾数的32.3%。春季木洞江段鱼类多样性高于秋季。调查表明，木洞江段既是圆筒吻鮈等特有鱼类的产卵场，也是鲤、鲫、长吻鮠、粗唇鮠、黄颡鱼等经济鱼类的育肥场，具有重要的生态功能。2）空间上，木洞江段鱼类资源主要集中在深沱水域（如王家沱、温家沱），同时洪水脉冲有利于鱼类资源的纵向扩散；昼夜节律上，鱼类活动高峰发生在夜晚。由于木洞及以上江段的鱼类繁殖活动，8月下行鱼类数量多于上行数量；随着三峡水库蓄水运行，10月上行鱼类数量多于下行数量。3）木洞江段鱼类分布主要与水深、底质和透明度等生境特征有关。圆筒吻鮈、长鳍吻鮈、宜昌鳅鮀、紫薄鳅、小眼薄鳅、犁头鳅等种类偏好于水体较深，河床质为石质的区域，而达氏鲌、光唇蛇鮈、蛇鮈、鲤、鲫等种类偏好于水体较浅，透明度较小的区域。4）结合项目成果及前期工作基础，提出了三峡库尾江段的鱼类保护措施与建议，如开展长江上游梯级工程的联合生态调度，确保库尾江段鱼类繁殖期所需的自然流态；开展沿岸带淤积区的生态修复，提高生境适宜性；加强三峡库区外来鱼类的监测与控制等。相关成果可为梯级工程影响下的鱼类多样性保护和栖息地的生态修复提供科学依据。