Hydrodynamic thresholds during the spawning period of Schizothorax prenanti and habitat restoration study

Hydrodynamic thresholds are critical yet unquantified for spawning habitats of endangered fish in regulated rivers. This study integrates laboratory flume experiments with field investigations to establish species-specific requirements for Schizothorax prenanti (S. prenanti)—a vulnerable endemic fish in the upper Yangtze Basin. Video-tracking analysis identified optimal spawning flow velocities (0.63–1.29 m/s) and water depths (0.15–0.97 m), validated in Jinsha River tributaries. To rehabilitate degraded habitats, boulder clusters were deployed in priority reaches, significantly altering local hydraulics: minimum flow velocity decreased by 17.89 % while maximum velocity increased by 29.00 %, with water depth extremes rising 7.56–9.67 %. Hydraulic habitat assessment demonstrated post-restoration weighted usable area (WUA) gains of 13.49–21.08 %, confirming enhanced spawning suitability. This study provides empirical support for boulder-cluster restoration as an effective way to enhance S. prenanti spawning habitat and offers practical targets for conservation and river-ecosystem management. The findings contribute to the broader goals of biodiversity conservation and sustainable river restoration.