Abstract: Based on the monitoring data of catches, fish passing and environmental factors of Duobu Hydropower Station in Xizang, we screened out the factors affecting the passing of protected fish species. The results showed that: (1) The same-side vertical slit fishway design adopted by the Dobu fishway can better meet the fish passage of the river section. (2) The amount of fish passage in May was significantly greater than that in June. The active period of Schizothorax macropogon Regan, Schizothorax waltoni Regan and Schizopygopsis younghusbandi Regan generally occurred before June. The active period of Schizothorax o’connori Llord could be up to mid-June. (3) Among the examined water quality indices, higher dissolved oxygen content, lower pH, and smaller turbidity were beneficial for fish passage. The increases of water temperature had stronger inhibitory effects on the amount of passage of Schizothorax waltoni than other fish species. Schizothorax o’connori was more tolerant to the reduction of water quality than other three fish species. (4) Among the project operating parameters, the increases and drastic changes in the inflow, downstream flow and tailwater level had greater negative impacts on fish passage. Decreasing and fluctuating of average head was associated with the reduction of passage for Schizothorax waltoni, Schizopygopsis younghusbandi, and Schizothorax o’connori. Decreasing and fluctuating of reservoir water level had an inhibitory effect on dam-crossing activities of Schizothorax waltoni. Schizothorax o’connori adapted to a greater range of changes in the project operating parameters than other fish species. (5) The change of hydraulic parameters in the fishway had no significant effect on Schizopygopsis younghusbandi. Small water depth and high variability of fish entrance were conducive to attracting Schizothorax macropogon to pass through the fishway. Greater flow, water depth, and fish outlet flow velocity in the fishway as well as their greater variability were more favorable to the passage of Schizothorax waltoni. Drastic changes in flow and flow rate in the fishway were more favorable to the passage of Schizothorax o’connori.

Key words: Xizang, Duobu Hydropower Station, fishway, influencing factor