Study on Fish Diversity in Chongqing Jiangbei Section of Upper Reaches of Yangtze River Based on Environmental DNA Technology.

To understand the fish diversity in the upper reaches of the Yangtze River in Chongqing, environmental DNA (eDNA) technology was used to analyze the fish diversity during a one-year water body sampling period from April 2021 to January 2022. The results showed that a total of 82 fish species (including Oreochromis, which was not identified to species level). 7 orders and 19 families and 63 genera were detected in the Jiangbei Section of the upper Yangtze River in Chongqing including 5 species of national key protected animals, 8 species of endemic animals in the upper reaches of Yangtze River and 8 exotic species. The number of fish species showed a seasonal trend of autumn > winter > summer > spring, among which Cyprinus carpio, Hypophthalmichthys nobilis, Pelteobagrus fulvidraco, Hemiculter tchangi and Ctenopharyngodon idella were all detected in the four seasons and had high sequence abundance. The Chao1 and ACE indices differed significantly between seasons (P<0.05) and the alpha diversity index in winter was higher than the three other seasons. The PCoA results showed that the heterogeneity between spring and summer samples was low and the species composition was similar, while the fish species composition in autumn and winter were significantly different and the heterogeneity was high. RDA analysis showed that water level, water flow and water temperature were the main factors affecting the seasonal distribution of the fish community. They were negatively correlated with water temperature and water flow, positively correlated with water level in spring and summer, and negatively correlated with water temperature and flow and positively correlated with water level in winter. Spearman's correlation test showed that water temperature was significantly negatively correlated with Shannon diversity, Chao1 index and ACE index (P<0.01); conductivity was negatively correlated with Coverage index (P<0.05), and water temperature, water flow was negatively correlated with Simp- son diversity (P<0.05). Overall, this study shows that eDNA technology can rapidly analyze fish species composition and distribution, and has great potential and importance in the monitoring fish resources in the Yangtze River. [ABSTRACT FROM AUTHOR]