Abstract: Lake Taihu is the third largest freshwater lake in China. The fish community and the correlations between the fish species and environmental factors were investigated from 2018 to 2020. Customized gillnets and fixed cages were arranged to conduct 40 sampling events at the 24 sampling points in different regions of the lake. Taxonomic identification of the 4 160 specimens revealed that all the bony fishes, belong to 6 orders, 11 families, 37 genera, and 52 species. Coilia nasus (specifically a geographical/ecological population formerly recognized as Coilia ectenes taihuensis) dominated in numbers, and Cyprinus carpio dominated by weight. The lake's fish community is characterized by a dominance of small-sized surface-dwelling fishes and a decreasing proportion of carnivorous fishes. Cluster analysis of the fish community data (Ward's minimum-variance method) showed different assemblages in the northwestern and southeastern areas of the lake. Canonical correspondence analysis of environmental variables in relation to the fish community data found that water clarity (SD), pH, a fish-based index of biotic integrity (F-IBI), water temperature, and the chemical oxygen demand based on potassium permanganate (COD_Mn) were key factors. COD_Mn was the main environmental factor affecting several of the predatory and omnivorous species. Hemiculter leucisculus and Culter alburnus were mainly influenced by SD; Tachysurus fulvidraco by pH; and Sarcocheilichthys nigripinnis by F-IBI. On the basis of the present aquatic environment and the existing methods for biomanipulation of fish communities, management efforts to increase the carnivorous fish such as the species of Culter and Cultrichthys would reduce the dominance of Coilia nasus, thereby expanding the zooplankton population available to suppress planktonic algae.

Key words: Lake Taihu, cluster analysis, multivariate data, polluted condition, biomanipulation