Integrating Environmental Suitability and Functional Trait Analysis to Assess Relative Invasion Risk of Non-Native Fishes in the Pinglu Canal Region

Artificial canals enhance regional navigation capacity and promote economic development, but they can also alter connectivity between previously isolated aquatic systems, facilitating the movement of non-native species across drainage basins and increasing invasion pressure. The Pinglu Canal, a river-to-sea corridor connecting the Xijiang River with the Beibu Gulf in China, may create new opportunities for the dispersal and establishment of non-native fishes, yet the relative invasion risk of non-native fishes in this region remains poorly understood. This study integrated species distribution models with functional trait analysis to screen 25 non-native fish species for environmental suitability and biotic compatibility. An integrated index was subsequently developed to quantify relative invasion risk by combining these two dimensions. The models showed good to excellent discrimination under random-split evaluation, with temperature emerging as the dominant environmental factor shaping predicted suitability. Predicted suitability was shifted toward higher values for 12 species, with peaks between 0.50 and 1.00. Their predicted distributions were grouped into four spatial patterns, including a southward increase in suitability for six species that reflected regional temperature gradients. Trait-based analysis grouped the 25 species into four functional configurations based on the mean distance to the native assemblage and the minimum distance to the nearest native species; these configurations were used only to compare species positions in functional space. The integrated assessment classified eight species as high-risk, eight as medium-risk, and nine as low-risk; these categories represent relative rankings among the 25 candidate species within the Pinglu Canal region. Representative high-risk species included Cirrhinus mrigala and Coptodon zillii. These findings identify candidate species requiring priority surveillance and provide a basis for targeted prevention and management of non-native fish invasions in the Pinglu Canal.