Exploring the fish assemblage structure in the process of ecological stocking: A case study of Daye Lake

As human activities cause water eutrophication and overfishing, which had a serious impact on fish resources, fish diversity showed a downward trend. In order to understand the changes of fish assemblage structure in the process of ecological stocking and effectively, the existing fish community in Daye Lake which was divided into 9 sites was evaluated in the summer of 2019 and 2020, and fish resources were investigated by traditional fishing and eDNA metabarcoding technology. The results showed that 33 species belonging to 18 genera, 6 families and 4 orders of fish were investigated in Daye Lake based on traditional fishing methods. Among them, Hypophthalmichthys molitrix and Hypophthalmichthys nobilis were the dominant species in Daye Lake all year round, and the dominant group was omnivorous, middle-lower fish. And the fish communities at the same point at different times were similar, the separation degree of fish communities was relatively high among different locations. Based on eDNA metabarcoding technology, the mitochondrial COI (cytochrome oxidase I) and 12S rRNA gene regions of eDNA were amplified respectively. A total of 10 species of freshwater lake fish were detected, of which 7 were detected together with traditional methods. Alpha and Beta diversity analysis showed that GJQ had the lowest species diversity, DW and LJH had the highest species diversity, and the biodiversity of adjacent sites was relatively similar. This study proved that ecological stocking will not have a great impact on the diversity of fish populations in lakes. At the same time, it proved the effectiveness of eDNA metabarcoding technology in fish diversity investigation.