Characteristics of surface flow field and substrate in the spawning ground of Schizothorax grahami

The Spawning ground is a crucial habitat for fish, and the physical characteristics of the habitat are important for fish life history. In this paper, Large-Scale Particle Image Velocimetry (LSPIV) was used to measure the surface flow field and the substrate (particle size and mineral composition) in the spawning ground of Schizothorax grahami. Based on the literature and consideration of experimental feasibility, two spawning grounds in the source of the Chishui River were selected—Erlongqiangbao (located in the mainstream) and Bamaoba (located in the tributary), two and three cross sections of each river section were analyzed respectively. The results show that Erlongqiangbao first flows in the direction of “southeast-northwest” and then “southwest—northeast” after crossing the bridge; the maximum velocity of the reach is 3.374m/s. The size of the substrate is mainly less than 1mm in the upstream section of Erlongqiangbao, both 25-50mm in the middle and downstream, and the substrate type mainly is quartz and calcite; Gushangtian flows in the direction of “southwest-northeast,” the maximum velocity of the reach is 1.537m/s, the size of the substrate is mainly greater than 50mm in the upstream, and 25-50mm in the middle and downstream, the substrate type mainly is quartz, calcite, and dolomite. The mineral compositions of the two spawning sites were analyzed by principal component analysis. Quartz and anorthose are more than 1 in composite scores, respectively ranked first and second, indicating that they play a dominant role in the mineral composition. This study could provide basic data and ideas for restoring S. grahami spawning ground.