Spatiotemporal Variation Of Fish Community Structure And Its Driving Factors In The Backwater Area Of Xiaojiang River

Large-scale water conservancy projects have high social and economic benefits,and does great contributions to protect human life and property safety and facilitate human life.However,their destructive effects on river ecosystems usually be observed.Based on the fish resource surveys and habitat data collections conducted in the backwater region of Xiaojiang River from May to July and October to November in 2013 and 2019,respectively,the variations in the fish sources in the backwater region of Xiaojiang River are analyzed.Meanwhile,the relationship between spatial-temporal variations of abiotic factors and fish community structures in the backwater region of Xiaojiang River is quantified using the multivariate analysis methods.With those methods performed,the spatial-temporal change character of fish community structures and its driving factors in the Xiaojiang’s backwater region after the normal storage of the Three Gorges Reservoir are revealed.The main studied results are shown as follows:(1)A total of 74 fish species belonging to 7 orders,15 families and 56 genera are collected from the backwater area of Xiaojiang River in 2013 and 2019,including 15 dominant species,7 endemic species and 5 exotic species.At the taxonomic level,fish species are mainly comprised of Cypriniformes and Cyprinidae.In terms of ecological composition,the dominant fishes mainly are eurytopic fishes,benthic fish,omnivorous fishes,and fish species that spawn the demersal eggs.(2)After the impoundment and operation of the Three Gorges reservoir(TGR)for many years,the fish resources in the river sections of the backwater area of the Xiaojiang River have changed significantly between years: the numbers of endemic and rheophilic fish species,as well as fish species that spawn the drifting eggs,have decreased,while the number of exotic fish species have increased.(3)The fish community structures in the perennial backwater area have changed significantly in 2019,while no significant difference in the fish community structures in the river section of the variable backwater area of Xiaojiang River are observed between 2013 and 2019.(4)The fish community structures in the perennial backwater area of Xiaojiang River show obvious seasonal variation characteristics in 2013,but the seasonal variation characteristics become less obvious in 2019;the fish community structures in the variable backwater area of Xiaojiang River show obvious seasonal variation characteristics in 2013 and 2019.(5)Total phosphorus content,phosphate content,water temperature and flow velocity significantly affect the temporal and spatial change pattern of fish community structures in the backwater area of Xiaojiang River;phosphate content and water temperature are the two key factors driving the change of fish community structures in the backwater area of Xiaojiang River...