Abstract: By using self-made test chamber and the method of increasing velocity, this paper studied the induction velocity of juvenile grass carp (Ctenopharyngodon idellus) (body length 964±3.12 cm, body weight 20.97±16.71 g), silver carp (Hypophthalmichthys molitrix) (body length 10.60±3.45 cm, body weight 24.37±18.61 g), and darkbarbel catfish (Pelteobagrus vachelli) (body length 11.54±1.46 cm, body weight 20.98±6.94 g) at water temperature 21±1 ℃. The induction velocity of the juvenile grass carp, silver carp, and darkbarbel catfish was (8.21±0.68), (6.74±0.84), and (33.11±3.06) cm·s^-1, and the relative induction velocity was (0.91±0.22), (0.67±0.15), and (2.9±0.29) BL·s^-1, respectively. No significant difference was observed in the induction velocity between juvenile grass carp and silver carp (P>0.05), but the induction velocity of juvenile darkbarbel catfish was four times higher than that of the juvenile grass carp and silver carp. It was suggested that the juvenile grass carp and silver carp were more sensitive to the water velocity than the juvenile darkbarbel catfish. This study could provide scientific reference for designing the fish way and determining the trawling speed.

Key words: TN, TP, AP., NH₄⁺-N, Spartina alterniflora wetland