Abstract: To investigate the swimming ability of two Schizothorax species in the Yalung River and provide basic parameters for the studies on fish behavior and the design of fish passage, we exa-mined the induced velocity, critical swimming speed, and burst swimming speed in Schizothorax dolichonema and Schizothorax prenanti with incremental velocity method and the durable swimming speed in S. dolichonema with fixed velocity method. The results showed that the induced velocity of both species increased first and then plateaued with the increases of body length, with the maximum values being lower than 0.2 m·s^-1. The critical swimming speed and burst swimming speed of S. dolichonema were (0.81±0.20) and (1.49±0.26) m·s^-1, respectively, while the relative critical swimming speed and the relative burst swimming speed were (4.90±1.73) and (9.77±1.72) BL·s^-1 (BL: body length), respectively. For S. prenanti, the critical swimming speed and burst swimming speed were (0.73±0.24) and (1.17±0.39) m·s^-1, respectively, while the relative critical swimming speed was (6.88±2.82) BL·s^-1, and the relative burst swimming speed was (11.75±2.77) BL·s^-1. The swimming duration of S. dolichonema was negatively correlated with the flow velocity of 0.7-1.5 m·s^-1, and the relationship between fatigue time (T) and flow velocity (V) was fitted into lgT=-2.52V+5.59. The relationship between expected fishway length (d) and the tolerable maximum average flow velocity (V_{f max}) was accordingly derived to be V_{f max}=-0.17lnd+1.74. Taken together, the fishway targeting S. dolichonema and S. prenanti was recommended to generate the in-channel velocity larger than 0.2 m·s^-1, while the velocity at the entrance and verticle slot should be 0.73-1.67 m·s^-1, and the main-flow velocity in rest pools should be 0.2-0.7 m·s^-1.

Key words: Schizothorax dolichonema, Schizothorax prenanti, swimming ability, fishway design