Abstract:

Aims: The Kansu Corridor serves as a critical ecological protection area in northwest China. This study aims to investigate the fish diversity and resource status of the interior drainage systems within this region. 

Methods: Between April 2019 to October 2023, eight fishery resource surveys were conducted at 25 sampling sites across inland river basin of the Kansu Corridor. The relative importance index (IRI) was used to determine the dominant species of the population. Fish diversity was analyzed using the Margalef species richness index, Shannon-Wiener diversity index, Simpson dominance index and Pielou evenness index. The similarity matrix constructed based on Bray-Curtis similarity coefficient was used to cluster and sort the distribution characteristics of fish using non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) was employed to examine the gradient relationships between fish community composition and environmental factor using Canoco 5.0 software. 

Results: A total of 9,743 fish belonging to 4 orders, 8 families, 20 genera and 29 species were identified. Among them, 12 species were indigenous, including Gymnocypris chilienensis and Schizopygopsis pylzovi, which are under Gansu Provincial protection. Schizopygopsis huanghe was identified as a new recorded species in the interior drainage of Kansu Corridor, and 5 species, including Triplophysa yarkandensis and Silurus soldatovi, are classified a vulnerable or near-threatened under the Red List of Biodiversity of China. The fish populations were predominantly composed of small-sized species, with Gymnocypris chilienensis, Triplophysa hsutschouensis and Carassius cuvieri as the dominant species. Notable differences in dominant species were observed across different river systems and temporal intervals. The fish diversity in the inland river system of Kansu Corridor was generally low across the inland rivers. The Margalef species richness index was the highest in summer (2.215). While the Simpson dominance index peaked in autumn at the 0.715. Both Shannon-Wiener diversity index (1.463) and Pielou evenness index (0.716) reached their maxima in spring. Among the rivers, the Heihe River exhibited the highest species richness index of Margalef (2.767 ± 1.455) and Shannon-Wiener diversity index (1.549 ± 0.432), whereas the Shulehe River recorded the highest Simpson dominance index (0.755 ± 0.060) and Pielou evenness index (0.807 ± 0.095), respectively. The NMDS analysis revealed significant differences in fish species composition between the upper and middle-to-lower reaches of rivers. Redundancy analysis indicated that total phosphorus was primary environmental factor influencing fish community structure. 

Conclusion: Compared with the survey data from the 1980s, the distribution areas of Gymnocypris chilienensis and Triplophysa yarkandensis have been reduced, while the distribution areas of other Triplophysa species have remained relatively stable. Key factors affecting fish diversity and distribution in the region include water resource scarcity, invasive spices, and water conservancy projects.

Key words: Kansu Corridor, interior drainage, species diversity, fishery resources, protection management