鄱阳湖物理生境特征及其对鱼类群落结构的影响

湖泊鱼类群落结构与物理生境特征密切相关。为了探究鱼类群落结构与物理生境特征之间的关系，在鄱阳湖设立17个采样点，通过采集鱼类样本研究其群落结构，并利用遥感技术分析样点物理生境特征（包括岸线分形维数、距离指数和高程值）及其空间区域差异。结果表明，依据17个采样位点的物理生境特征，鄱阳湖丰水期物理生境空间上可以划分为3个区域，分别为北方区、南方区和主湖区，但枯水期鄱阳湖生境没有显著的区域划分规律。丰水期鄱阳湖鱼类可以分为北方群、南方群和主湖区群3个类群，而枯水期鱼类组成没有明显规律。从功能类群上看，鄱阳湖鱼类以杂食性、湖泊定居性和偏好于底层以及中下层栖息的中小型鱼类为主。不同区域的鱼类功能群之间存在时间和空间上的变化，北方区和南方区鱼类功能群组成相似，主湖区与北方区和南方区存在差异。总体上，鱼类群落结构的时空变化和差异与物理生境特征具有良好的一致性；未来鄱阳湖鱼类的保护工作需要关注湖泊物理生境特征，不同区域应制定不同的保护措施。

Physical Habitat Characteristics of Poyang Lake and Their Influence on Fish Community Structure

Poyang Lake is the largest freshwater lake in China, and one of the three lakes that still have a natural connection to the main stem of Yangtze River. The fish community structure of lakes is closely related to its physical habitat. In this study, based on fish survey data and ArcGIS analysis, we explored the relationship between fish community structure and physical habitat characteristics in Poyang Lake. We then explored differences in composition and functional groups of fish community within the different habitats. The fish survey was carried out at 17 representative sampling sites in January (dry season) and July-August (rainy season) 2018. The fish community structure was analyzed by cluster analysis and remote sensing technology was used to analyze the habitat characteristics of each sampling site, including fractal dimension, distance index, elevation value and the spatial difference of the regions. Based on physical habitat characteristics at the 17 sampling sites, the physical habitat of Poyang Lake in rainy season clustered into three zones: northern, southern and main lake. However, the sampling sites clustered irregularly in dry season. In the rainy season, the fish community fell into three groups that correlated significantly with the three habitat zones, but in the dry season no regularity in fish community composition was detected. Fish functional groups were described as follows: the community is dominated by omnivorous fish (> 50% of total fish species); bottom and middle layer fish were the main groups (>70% of the total species); limnophilic species was the primary ecological group and small and medium-sized fish dominated. The composition of fish functional groups presented obvious spatial and temporal differences. The fish functional groups of the northern and southern zones were similar and differed from the functional group composition of the main lake. Our study revealed the extent to which fish community structure is shaped by physical habitat in Poyang Lake. This will allow physical habitat characteristics to be more effectively used to guide future fish conservation efforts.