Abstract: An investigation of fish species composition and assemblage structure was conducted in the Lake Erhai from 2014 to 2015, and the environmental factors were determined at the same time. 24 species of fish belonging to 6 orders, 11 families and 21 genera were collected, including 19 exotic species and 5 native species. There were 13 species from Cyprinidae and 2 species from Gobiidae, which accounted for 54.2% and 8.3% of the total species, respectively, with only one species in each of the remaining 9 families. The spatial distribution of fish assemblages consisted of two major types: species living in pelagic zones and those in littoral zones. The fish density and biomass in both pelagic zones and littoral zones were higher in May and July than those in January and September. Compared with littoral zones, both the density and biomass in pelagic zones were much higher. Notably, the structure of fish assemblages was found to be miniaturized and simplified. As revealed by the index of relative importance (IRI), five dominant species were Neosalanx taihuensis, Hemiculter leucisculus, Hypophthalmichthys molitrix, Carp cyprinus and Carassius auratus. Three diversity indexes showed low assemblage diversity throughout the year; the spatial distribution of Shannon index (H) and Pielou’s evenness index (J) had a trend similar to that of fish density and biomass. The spatial differences in fish density and biomass as well as assemblage diversity were significant (P<0.05), but the seasonal differences were not significant (P>0.05). Furthermore, water depth, dissolved oxygen and eutrophication were the main environmental factors affecting the spatiotemporal distribution of fish assemblages.

Key words: eco-environment quality, contiguous special poverty-striken area, economic development composite index, coupling coordination degree, coupling coordination type.