4.3 Implications for conservation
This study was the first to describe the spatial-temporal variation of fish assemblages in mountain streams in the southwest China. Information obtained from this study will enhance our understanding of the variation in fish assemblages, and then help to develop strategies for future fish diversity protection in such mountain streams. A total of 21 fish species were collected during the sampling period. Among which, S. macrolepis and S. prenanti have been considered as vulnerable. These species used to be important commercial targets in Ren River basin. However, compared to history records, their distribution range has shrunk significantly, and their population size has declined seriously (Zeng 1991). In addition, the miniaturization tendency of these two species has become evident (Zeng 1991). The survive prospect of S. prenanti is gloomier, as only three specimens of were collected during our study period. Overfishing might be the main reason responsible for this phenomenon (Zeng 1991). To protect these vulnerable species, the local government should strengthen fishery management and fight against illegal strictly. In addition, the present study indicated that fish assemblages in streams of the Ren River basin were influenced mainly by landscape factors, such as altitude and C-link. Specially,R . oxycephalus , a representative cold-water species, was restricted to headwaters and small tributaries with higher elevation. This species is an excellent bioindicator species low-temperature water and a good model species for studying freshwater fish biogeographic, because of their typically low dispersal ability and restriction to small mountain habitats (Yu et al. 2014). Climate change and anthropogenic interferences have seriously threatened this species (Yu et al. 2014). Therefore, to maintain the stability of fish assemblage structure in such stream ecosystems, human activities that will destroy the naturality and connectivity of stream habitat, such as deforestation, dredging and damming, should be forbidden strictly.
Acknowledgements This study was supported by the National Natural Science Foundation of China (31400359), Natural Science Foundation of Shanxi (2018JQ5121) and Sino BON‐Inland Water Fish Diversity Observation Network. The authors are grateful to Lixia Shi, Zhi Zhang, Liangxia Su, Nenghan Wang, Jian Zhang and Chunsen XU for their help in filed samplings.