Freshwater biodiversity is facing a great crisis due to the looming
threat of biodiversity loss. Some important target areas are difficult
to survey owing to their accessibility, making them susceptible to data
deficiencies. In this study, we surveyed 52 sites using environmental
DNA techniques to investigate fish biodiversity in the Chishui River
Basin of the Yangtze River. A total of 96,031 valid fish sequences were
read, resulting in the identification of 77 species belonging to six
orders, 62 genera, and 18 families. The dominant orders were
Cypriniformes, Siluriformes, and Perciformes. Among the identified
fishes, 71 were native and six were exotic, with the native fishes
including 16 endemic fishes from the upper reaches of the Yangtze River.
The upstream and downstream Shannon-Wiener indices differed
significantly, the Shannon-Wiener and richness indices of the
tributaries in the upstream section were significantly higher than those
of the tributaries in the downstream section, and we found that the
Datong River is the most diverse secondary tributary of the Chishui
River. Among the environmental factors in the Chishui River Basin,
altitude and electrical conductivity had the greatest influence on fish
diversity (P <0.01), whereas human factors had little effect.
Our findings highlight the application of environmental DNA technology
to modern biodiversity surveys and illustrate that the Chishui River
Basin is primarily affected by environmental factors at this stage.
However, continuing efforts are needed to protect freshwater
biodiversity, and additional research is required to better understand
the complex interplay between human activity and environmental factors.