Effects of dams and fish passage facilities on the longitudinal movement of Coreius guichenoti in the Jinsha River Basin

The construction of hydropower dams has provided energy, water management, and flood control, yet it has also presented considerable ecological challenges. In the Jinsha River Basin, the construction of hydropower dams has disrupted the longitudinal movement of Coreius guichenoti. This study employs the Dendritic Connectivity Index for Potadromous (DCI_P) to evaluate the impact of dams on the connectivity of this species and to investigate the potential for enhancing connectivity through fish passage facilities under scenarios of high and limited efficiency. The results demonstrate a notable decline in DCI_P scores between January 1990 and January 2024, with a reduction from 100 to 11.52 (high efficiency) and 9.68 (limited efficiency). In the future, scores are expected to improve slightly to 13.21 (high efficiency) and 9.7 (limited efficiency), as all dams and upstream facilities are completed. Furthermore, incorporating a single upstream or downstream facility can enhance connectivity, albeit to a limited extent. For the three plans of adding bidirectional facilities at all dams, scores could reach 100 under high efficiency, but they only reached 12.83 under limited efficiency. In both scenarios, the highest DCI_P score improvements in Phase I of Plans 1 and 2, which added only one type of facility (either upstream or downstream), were lower than in Plan 3 (an equal number of facilities), which added both types simultaneously. The study emphasizes the importance of constructing efficient bidirectional fish passage facilities to ensure the effective longitudinal movement of Coreius guichenoti. The results are related to mitigating the negative impacts of dams on connectivity and can provide a reference for species conservation and river health management.