Abundance and spatial variability of invasive fishes related to environmental factors in a eutrophic Yunnan Plateau lake, Lake Dianchi, southwestern China

Abstract

Lake Dianchi is the largest freshwater lake on the Yunnan Plateau and the sixth largest one in China. In recent decades, a number of non-native fish species have been introduced into the lake intentionally or accidentally while human-accelerated eutrophication has been occurring. In this study, we provided a whole-lake assessment of species composition and abundance of the accidentally-introduced fishes, and described the spatial variability of invasive small fish community in relation to eight physicochemical environmental factors. Fish were sampled quantitatively at 30 sites throughout the lake with multiple mesh-sized gillnets in the autumn of 2008. A total of 2,050 individuals from seven non-native small fish species were captured. Thin sharpbelly Toxabramis swinhonis and piper halfbeak Hyporhamphus intermedius were recognized as dominant species, followed by barcheek goby Rhinogobius giurinus, topmouth gudgeon Pseudorasbora parva and redfin culter Culterichthys erythropterus, according to their abundance and occurrence. Principal component analysis (PCA) suggested that the fish community structure in the northern part was distinct from those in the middle and southern parts of the lake, corresponding to the increase of lake eutrophic level from south to north. Redundancy analysis (RDA) showed that redfin culter, piper halfbeak and thin sharpbelly were positively related to nutrient variables (total phosphorus, total nitrogen), while topmouth gudgeon and barcheek goby were associated with relatively higher secchi depth and lower nutrition level. Water depth seemed to have moderately negative influence on spatial distribution of all the fish species. Regression tree analysis was applied to visualize decision rules for the prediction of fish abundances (CPUE, ind/fishing pass/h) from key environment variables, and explained 51.5-69.0 % of the total variance of response values. The details of these findings are beneficial to understanding the establishment of invasive fish in degraded environment, and to developing suitable conservation strategies for the restoration and management of fish resources in Lake Dianchi as well as the other lakes of Yunnan Plateau.