Environmental DNA Reveals the Fish Community Structure Exhibited Instability and Trend of Miniaturization in the Xijiang River Basin of the Guizhou

The seasonal monitoring of fish communities was conducted in the Xijiang River Basin of Guizhou Province using environmental DNA (eDNA) metabarcoding technology. A total of 97 fish species were identified during the 2023 survey, representing a detection rate of 61.94% compared to historical records. The findings demonstrated the following: (1) Fish communities exhibited significant spatiotemporal heterogeneity, with species diversity and composition varying seasonally and spatially; (2) human activities, such as reservoir construction, have led to the potential trend toward miniaturization of fish populations and pose a severe threat to the survival of indigenous species; (3) water NH 3 -N, altitude, and pH emerged as the key environmental factors influencing community structure. This research elucidated the dynamic characteristics of riverine fish communities in karst mountainous regions and provided a scientific foundation for the adaptive management of river basin ecosystems. Furthermore, this study represents the validation of eDNA technology's monitoring efficiency in karst areas characterized by complex geographical environments, thereby confirming its application value in assessing biodiversity in mountainous aquatic systems.