Habitat suitability of Schizothorax wangchiachii in the Heishui River of the lower Jinsha River tributary, China.

As an important component of aquatic ecosystem, fish habitat is crucial for maintaining aquantic ecosystem, species diversity, and sustainable fisheries. To reveal the suitability of habitat factors and distribution patterns of Schizothorax wangchiachii in the Heishui River of the lower Jinsha River tributary, we selected the habitat indicators by the Spearman correlation single tail test, calculated the fish habitat suitability index by the random forest algorithm and weighted average method, based on the fish catch data and 16 related environmental factor data collected from 2018 to 2019. The results showed that the optimal range of water temperature, water depth, and altitude for S. wangchiachii was 16.3-16.8 ℃, 35-60 cm, and 637-816 m, respectively. From the upper reaches to the lower reaches, the habitat suitability of S. wangchiachii showed a longitudinal increasing trend. The proportion of the habitat quality below the good standard was 70%, while the proportion reaching the good and very good stan-dards was only 30%. The habitat of S. wangchiachii was mainly distributed in the natural flowing river sections with high hydrological connectivity of the river course, shallow water depth, abundant bait organisms and slow flow rate. The obvious spatial differences of its habitat suitability might be caused by human disturbances such as the construction of small dams.