Spring fish diversity in fluctuating backwater zone of Three Gorges Reservoir, Upper Yangtze River using eDNA metabarcoding

Abstract

[Objective] Continuous dynamic monitoring of fish resources in the fluctuating backwater zone of the Three Gorges Reservoir is essential for evaluating the effectiveness of conservation measures and for formulating targeted management strategies. Against the backdrop of the 10-year fishing moratorium on the Yangtze River, non-invasive environmental DNA(e DNA) metabarcoding offers an efficient and convenient means of acquiring information on fish assemblages. [Methods] The Guangyangba section in the fluctuating backwater area of the Three Gorges Reservoir, the Upper Yangtze River was selected as the study area. The e DNA metabarcoding was employed to investigate fish diversity within the fluctuating backwater zone of the Three Gorges Reservoir, analyze the fish community composition, and assess fish species within the area, thereby providing data support for conservation of fish diversity in the fluctuating backwater zone. [Results] A total of 63 fish species were detected by e DNA metabarcoding, belonging to 5 orders, 10 families, and 48 genera, with Cypriniformes being the most abundant, accounting for 73 % of all records. The species with relatively high relative sequence abundance included Cyprinus carpio(common carp), Hypophthalmichthys nobilis(bighead carp), Ancherythroculter wangi, and Ctenopharyngodon idella(grass carp). Key environmental factors driving the spatial distribution patterns of fish communities were identified as flow velocity and conductivity. α-diversity among fish in the Guangyangba section of the fluctuating backwater zone in the Upper Yangtze River exhibited minimal variation, with an average Shannon diversity index of 1. 67 and an average Simpson diversity index of 0. 63. β-diversity among different sampling sites was governed primarily by turnover components. Resident species favouring slow-flow habitats and those producing demersal eggs dominated the Guangyangba section. [Conclusion] The fish community structure in the fluctuating backwater zone of the Three Gorges Reservoir is undergoing a redistribution from a riverine to a river-reservoir ecosystem, with habitats preferred by rheophilic, rare, and endemic fish species of the Upper Yangtze River progressively shifting upstream towards the national nature reserve for rare and endemic fish species.

Keywords

environmental DNA / fluctuating backwater zone of Upper Yangtze River / fish community / diversity / ecological guild / environmental factors / conservation strategies / influence factors