Abstract: To explore the effects of water level and temperature on fish community structure and diversity in Qili Lake, four surveys were carried out at high water level (wet season), flat water level (normal period I, II) and low water level (dry season) during 2019-2020, with environmental factors being measured. A total of 47 species were recorded in the survey, belonging to 4 orders, 10 families, and 36 genera. Cyprinids accounted for 65.96% of total species richness. More than 60% of the species were freshwater sedentary fishes, mainly dwelling in the upper and middle waters. The community was dominated by plankton feeding fishes, with Pseudobrama simoni asthe predominant species. The mean fish species richness in wet season and normal season was 35 species and 33 species, respectively, which were significantly higher than the 22 species in dry season (P<0.05). The average abundance of fish caught in the high water period was 1008, which was significantly higher than that of 662 fish and 594 fish in the low water period (P<0.05). The average weight of fish caught in different water periods showed no variation (P>0.05). The diversity index and richness index in the wet season were significantly higher than those in the dry season (P<0.05), but the dominance index was significantly lower than that in dry season (P<0.05). The results of cluster analysis showed that fish species composition in the dry season was classified into the group I, and that in the wet season and the normal season was classified into the group II, with a significant difference between both groups (P<0.01). In general, the diversity of fish community in the high water season was higher than that in the normal water season and the dry water season. Water level, water temperature, total phosphorus, and transparency were important environmental factors driving fish community structure (P<0.05).

Key words: Qili Lake wetland, community structure, diversity, influencing factor, clustering analysis, redundancy analysis.