Conservation status of Chinese freshwater fishes and quantitative evaluation of extinction risk in the Schizothoracinae (Cyprinidae)

Freshwater fishes are a crucial component of freshwater ecosystems and play a vital role in maintaining aquatic ecological balance. China possesses a rich diversity of freshwater fish resources. Although there has been some research on ecology of Chinese freshwater fishes, specific mechanisms and quantitative analysis of their conservation status, particularly the extinction risk of Schizothoracinae, have not been sufficiently explored. Here, we utilized public datasets to conduct related analysis. The results show 1) Phylogenetic Isolation Index (PII): among 1591 Chinese freshwater fish species, ten species exhibiting the highest PII all belong to Nemacheilidae, 2) Threatened Status. Cyprinidae, which includes 199 threatened species, is the most severely threatened family, with approximately 28% of its species being at risk. In Schizothoracinae of Cyprinidae, 54.9% of species are at risk of extinction. Following Cyprinidae, Cobitidae, and Sisoridae have 53 and 19 threatened species, respectively. Extinction risk of Chinese freshwater fish is not randomly distributed among families; rather, the numbers of threatened species observed in these families align closely with expected levels. 3) Extinction Risk Mechanisms in Schizothoracinae: using Generalized Linear Models (GLM), we explored the association between multiple characteristics of Schizothoracinae and their extinction risk. This study represents the first comprehensive integration of the phylogenetic isolation index (PII), extinction risk non-randomness, and human disturbance to assess conservation priorities for Chinese freshwater fish. Results show that areas experiencing intensive human activity tend to have a higher presence of Near Threatened species, while Endangered species are mainly confined to less disturbed habitats. Our findings are of significant scientific importance and practical value for formulating effective conservation strategies for freshwater fishes, as well as for a deeper understanding of complex interactions within ecosystems.