Abstract: In this study, we examined the induction flow velocity for Schizothorax prenanti (body length: 26.3±1.1 cm), Schizothorax davidi (body length: 28.5±2.9 cm), and Triplophysa brevicauda (body length: 9.7±1.3 cm) in a Brett-type swimming ability test flume with the increasing velocity protocol. The results showed that the absolute induction flow velocity (AIV) was (10.2±2.3), (9.8±0.02), and (9.3±1) cm·s^-1 for Schizothorax prenanti, Schizothorax davidi,andTriplophysa brevicauda at the water temperature of 11.9-14.1 ℃, while the relative induction flow velocity (RIV) was (0.33±0.02), (0.32±0.08), and (0.96±0.09) BL·s^-1, respectively. The results of bivariate correlation analysis showed no correlation between AIV and RIV with body length (P>0.05) in Schizothorax davidi. By contrast, the AIV of Schizothorax prenanti andTriplophysa brevicauda was positively correlated with their body length, while the RIV of the two species was negatively correlated with body length. Results of one-way ANOVA showed that Schizothorax prenantiandSchizothorax davidi had no significant difference (P>0.05) but were both significantly different with Triplophysa brevicauda(P<0.05) in AIV. RIV values significantly varied across the three species (P<0.05). The rheotaxis of focal fish correlated exponentially with given flow velocities. Accordingly, the fish passage facilities targeting the three fish species in Dadu River are required to introduce a minimum flow velocity of 0.13 m·s^-1 in their mainstream zone, allowing for a 95% success rate in upstream migration. Our results can enrich the fish rheotactic behavior database and facilitate fish passage design in the Dadu River basin.

Key words: Schizothorax prenanti, Schizothorax davidi, Triplophysa brevicauda, inductive velocity, rheotaxis.