Analysis of fish resources status and diversity in the middle reaches of Tuojiang River

In order to explore the characteristics of fish community structure in the Middle Reaches of Tuojiang River before the "ten-year fishing ban", based on the catch monitoring data from ten sampling sites of this section from 2017 to 2020, the characteristics of fish species composition, ecological types, community similarity, biodiversity and community structure stability were analyzed. The results showed that 87 fish species were collected, belonging to 5 orders, 14 families and 52 genera. Among which 18 species were endemic to the upper reaches of the Yangtze River and 6 species were exotic, accounting for 20.69% and 6.90% of the total species respectively. The fish community was dominated by demersal fish, sunken eggs and omnivorous fish. According to index of relative importance (IRI), the dominant fish species were small fishes, such as Saurogobio dabryi and Cyprinus carpio. Shannon-Wiener index, Simpson index, Margalef index and Pielou index ranged from2.700 to 3.742, 0.873 to 0.968, 5.374 to 11.323, 0.737 to 0.887, respectively. As a result, the community distribution uniformity was high in the Middle Reaches of Tuojiang River. The results of cluster analysis and non-metric multidimensional scale ranking (NMDS) analysis showed that the fish community types of ten sections in the Middle Reaches could be basically divided into three groups at a certain level of similarity, as Lianhuashan,Maliuba industrial park and Tielugou sections formed one group, Wangumiao , Wulidian hydroelectric station, Zizhou Bridge, Yinshan, Second Water Plant and Xilin Ferry section formed one group; Tuo Bridge section formed one group independently. The abundance/biomass comparison curve showed that the fish community structure in Xilin Ferry and Tuo Bridge section was relatively stable, but moderately disturbed in the other sections. The results showed that compared with the historical data, the fish community structure in the Middle Reaches of Tuojiang River has changed significantly, the proportion of economic fish has decreased, and the fish individuals have become smaller and younger. This study could supplement the basic data of fish community informationin the Middle Reaches of Tuojiang River, and also provide theoretically scientific support for fish resource management and ecological evaluation of "ten-year fishing ban" in this section of the river.