Coreius guichenoti, once widely distributed in the upper reaches of the Jinsha River, has become a nationally protected species in China due to the profound impacts of cascade reservoirs. To assess the influence of substrate on the suitability of spawning habitat for C. guichenoti, this study develops a substrate-inclusive habitat model using fuzzy logic based on expert knowledge. Taking the Pingdi Town section of the lower Jinsha River—a historical spawning site for C. guichenoti—as a case study from March to July 2020, we simulated changes in the spawning habitat suitability index (HSI) and compared the results with those from traditional models that exclude substrate factors. The results showed that in the first and second halves of May, Weighted Usable Area (WUA) and Overall Suitability Index (OSI) increased by 42.31% and 38.73%, respectively, while MSP exhibited dramatic increases of 236.04% and 614.56%. These improvements were primarily observed along the riverbanks, where HSI increased by approximately 0.25. From a management perspective, the HSI results provide a scientific basis for optimizing ecological flow regulation. Incorporating substrate factors into spawning habitat models offers a more objective and comprehensive assessment of habitat quality. Habitat restoration measures, such as targeted substrate improvement in key riverbank areas, may further increase habitat suitability, providing additional opportunities for conservation planning in regulated rivers.

The annular flume is an ideal hydrodynamic test device for studying river sediment, and it has been widely used in recent years to study the movement patterns of sediment and other particulate matter. Annular flumes have made outstanding contributions to research in fields related to sediment transport and the diffusion and migration of pollutants. The existence of circumfluence structures in annular flumes leads to complex and variable flow structures. To obtain a more stable and controllable water flow structure, a sophisticated three-dimensional mathematical model based on the Fluent software was established to study the development law of water flow structure in the flume by changing the size of the annular flume speed ratio. The results show the following: (1) The overall trend of the simulation results basically matched with the measured results; the average relative error was 3.54% and the Nash efficiency coefficient was 0.9934, close to 1. The model calculation data were highly credible. (2) The axial flow velocity of the water tank gradually showed a “U”-shape distribution with the increase in the speed ratio. (3) When the speed ratio was R ≤ 0.17 (where the speed ratio R refers to the ratio of annular groove to shear ring speed), there was only one vortex in the tank; when the speed ratio was R > 0.17, there were multiple vortices in the tank, and the flow pattern was more complicated. (4) When the rotational speed ratio R = 0.28, the secondary flow intensity of the annular flume reached the lowest point, which was only 39.28% of the secondary flow intensity of the conventional annular flume. (5) It was determined that the annular flume water flow structure was most stable and controllable when the rotational speed ratio R = 0.24. The results of the study can provide a further theoretical basis for research on sediment dynamics and its related fields conducted by applying an annular flume.