禁捕前鄱阳湖鱼类群落多样性及环境影响因子研究

为掌握鄱阳湖鱼类群落特征，课题组于2020年春季(5月)、夏季(8月)、秋季(11月)和2021年冬季(1月)4个季度，在鄱阳湖10个区域5种生境开展鱼类资源调查研究，同步采集水环境样品。研究共采集鉴定鱼类67种，隶属于8目14科47属，其中鲤科鱼类物种数最多(41种)，占比为61.19%。基于不同分组，鱼类生态类型分别以定居性鱼类(67.16%)、杂食性鱼类(44.78%)、中下层鱼类(35.82%)占据优势。该群落以小型鱼类为优势类群，数量占比为68.70%；鱼类优势种共有6种，第一优势种为似鳊。鱼类群落结构在季节上存在显著性差异，春季鱼类物种多样性指数高于冬季。非度量多维尺度分析(NMDS)显示，空间上鱼类可划分为2个类群，分别为湖口区类群和草型湖区-湖汊区-湖心区-沿岸带类群。冗余分析(RDA)显示，总磷、叶绿素a和透明度是影响鱼类物种时空分布的关键环境因子。丰度/生物量比较曲线(ABC曲线)分析表明，鱼类群落受到严重干扰(W=-0.091)。本研究成果可为鄱阳湖禁渔效果评估和鱼类多样性保护提供科学依据。

Fish community diversity and environmental influencing factors in Poyang Lake before the fishing ban

As an important component of aquatic biodiversity, fish are the most sensitive and reliable indicator of ecosystem function in aquatic areas. Its growth and development are closely related to the environmental factors of the inhabiting waters, and have an important indicator of environmental changes. In order to grasp the characteristics of the fish community in Poyang Lake, we conducted fish resource surveys in ten regions of Poyang Lake involving five habitats and collected water environment samples simultaneously in spring (May), summer (August), autumn (November) of 2020 and winter (January) of 2021 before the comprehensive fishing ban. We identified a total of 67 fish species, belonging to 8 orders 14 families 47 genera, of which Cyprinidae had the the maximum no. of species, accounting for 61.19%. According to different groups, the dominant ecological types of fish were mainly lake sedentary (61.19%), omnivore (44.78%), and lower fish (35.82%). Small fish was the dominant group in this community, accounting for 68.70%, and the index of relative importance (IRI) showed that there were six dominant species, the first one was Pseudobrama simoni. Significant seasonal differences were observed in fish community structure (P<0.05), and the fish species diversity index in spring was higher than that in winter (P<0.05), because the diversity and richness of species were affected by seasonal factors. Changes in water temperature and water level may be the main reasons for affecting the spatial and temporal pattern of fish community diversity in Poyang Lake. Non-metric multidimensional scaling analysis (NMDS) showed that fish could be spatially divided into two taxa, namely the estuary taxon and the grassy-lake branch-lake center-coastal zone taxon. In redundancy analysis (RDA), we observed that total phosphorus, chlorophyll a and transparency were key environmental factors affecting the spatial and temporal distribution of fish species. With the change of hydrological rhythm in the lake area, with the increase of water level, nutrients flow into the lake area, providing a rich food source for fish, and fish feeding activities are enhanced. When the total phosphorus is too high, it will lead to eutrophication of the water body, and the nutrient load and suspended solids will limit the habitat and even survival of sensitive species. Chlorophyll a is an important indicator reflecting the change of phytoplankton content, and in spring, with the increase of temperature, the surface water temperature rises rapidly, and phytoplankton in the water body begins to multiply in large quantities, which is reflected in the increase of surface chlorophyll a content. Abundance-biomass comparison curve (ABC curve) analysis showed that the fish community was severely disturbed (W=−0.091). This study can provide a scientific basis for the evaluation of the effect of fishing ban and the conservation of fish diversity in Poyang Lake.