ABSTRACT
Freshwater biodiversity is facing a great crisis due to the looming
threat of biodiversity loss. Certain 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.
Keywords: Chishui River, environmental DNA, environmental
factors, fish biodiversity, human activities, influencing factors