Species diversity of fishes in the middle and upper reaches of the Yangtze River and impact of exotic invasions on fish communities

Fish species diversity is rich across the Yangtze River basin, but fishery catches are rapidly increasing in the past decades, and declining fish biodiversity poses risks for fishes resources. However, the degree of reduction in fish diversity and the change-drove factors of fish communities in the Yangtze River are still unknown. The data from investigation and the retrieved literatures were analysis the diversity and structure of fish community to explore the driving factors of fish diversity change and measure the change degree of fish diversity in the Yangtze River. Meanwhile, compared α and β diversity changes of fish communities at species and phylogeny levels during historical and current periods were analyzed. The results showed that 174 species, belonging to 92 genus, 22 families, and 9 orders were found in the main channel of the Yangtze River to date. Compared to historical period, 47 native species, and 27 endemic species decreased, but 11 invasive species increased in current period. The diversity of fish community in the upper stream was significant higher than that of the middle (P<0.05) and 43 species contributed to the diversity rates of community construction. All species and native species showed that the average taxonomic distinctness increased from history to the current at the α level, but the taxonomic distinct diversity decreased, and the loss of native species resulted in a decrease in community diversity. The β_sør values of the upper and middle communities showed significant changes at the β level, which was drivn by β_sne. The β_sne.phy that changed from 0.054 to 0.085 was mainly a contribution to the changes of β_sor.phy between the upper and middle communities from 0.290 to 0.314 at phylogenetic β level. The β_sor.phy for the native species did not change significantly, and the acquisition of exotic invasive species gave rise to changes in community taxonomic units, further resulting in significant changes between communities at the phylogenetic β level. By comparing the changes of fish diversity between historical and current periods, it suggested that the loss of indigenous species and the invasion of alien species had changed the spatial and temporal patterns of fish communities, and significantly affected the phylogenetic diversity of fish communities, which was expected to provide theoretical support for ecological restoration in the Yangtze River.