Spatial distribution and introduction pathways of non-native freshwater fish species in China

Non-native freshwater fish species are regarded as a key factor responsible for the degradation of freshwater ecosystems. Although research on China's non-native freshwater fish species has been conducted at the national scale, the spatial distribution and introduction pathways of these species in China remain unclear. To address this knowledge gap, this study compiled a dataset of non-native freshwater fish species across administrative regions in China. We first assessed the number of non-native freshwater fish species by taxonomy, geographical origin, introduction pathway, and province. There were 177 non-native freshwater fish species, belonging to 17 orders, 48 families, and 118 genera. The orders Cypriniformes (33.3%), Perciformes (28.2%), Siluriformes (10.2%), and Salmoniformes (6.2%) accounted for the largest proportion of non-native freshwater fish species. Eighty-nine nonnative species were introduced from other countries or regions, mostly from North America (31 species; 34.8%), Asia (20 species; 22.5%), Africa (13 species; 14.6%), Europe (11 species; 12.4%), and South America (10 species; 11.2%). Aquaculture was the most common introduction pathway. Non-native freshwater fish species were more widely distributed in southwest China. Our study showed that there were obvious differences in the number and composition of non-native freshwater fish species across various provinces in China. The variation in the number of non-native freshwater fish species across provinces in China was attributed to distinct geographical features, development of the aquaculture industry, and efforts to study non-native freshwater fish species. Therefore, comprehensive surveys and studies of non-native freshwater fish species are needed, which are of great importance for the management and control of non-native species invasions.