Abstract: Identifying the spatial pattern of fish assemblages is essential for the conservation and management of fish species diversity. Based on the data collected from 66 stream segments within the Chaohu basin in October 2013, we examined how stream fish assemblages varied spatially and assessed the classification strengths of three spatial schemes (i.e., subbasin, stream order and ecoregion) and fish taxonomic clusters in classifying fish assemblages. Our results showed that fish assemblages did not vary significantly among subbasins and stream orders but differed significantly among ecoregions. For the spatial schemes of subbasin and stream order, the mean withingroup similarity of fish assemblages was not significantly different from the mean betweengroup similarity, and thus the two spatial schemes presented very low classification strength for classifying fish assemblages. But for the spatial scheme of ecoregion, the mean withingroup similarity of fish assemblages was significantly higher than the mean betweengroup similarity, and thus its classification strength was relatively high. However, compared with the scheme of taxonomic clusters, the classification strength of the ecoregion scheme was relatively low. The results indicated that the spatial pattern of fish assemblages depended on the landscape conditions to a certain extent in the Chaohu basin, and also on the local environmental factors. In future research, it is necessary to further clarify the main environmental factors affecting the spatial pattern of fish assemblages in the Chaohu basin and the spatial distribution of these key factors, so as to provide scientific basis for the conservation and management of fish species diversity in the Chaohu basin.

Key words: principal component analysis, comprehensive evaluation., Fagopyrum tararicum, subordinate function, phosphorus tolerance