Effects of turbulence and velocity on the movement behaviour of bighead carp (Hypophthalmichthys nobilis) in an experimental vertical slot fishway

The vertical slot fishway (VSF) plays a major role in protection and restoration of migratory fishes at many migratory barriers. However, the VSF design greatly depends on fish response to hydraulics and swimming behavior, which are key to the design of effective VSFs for target fish species. This study evaluated the effects of hydraulic characteristics on movement behavior of bighead carp (Hypophthalmichthys nobilis) by combining spatial hydraulic distributions with fish movement trajectories in an experimental VSF. Fish spent more transit times in ranges of velocity (V) with 0.15-0.45 m/s, turbulent kinetic energy (TKE) with 0.020-0.043m(2)/s(2), turbulent dissipation rate (TDR) with 0.020-0.065m(2)/s(3) and strain rate (SR) with 2-7 s(-1) under different discharges (18.0L/s and 26.0L/s), respectively. Correlation were found between fish transit times and hydraulic variables of velocity (V) (Q = 18.0 m/s: r = 0.397, P < 0.01; Q = 26.0 m/s: r = 0.407, P < 0.01), turbulent kinetic energy (TKE) (Q = 18.0 m/s: r = 0.476, P < 0.01; Q = 26.0 m/s: r = 0.469, P < 0.01). TKE and V were the key hydraulic parameters associated with the fish transit movement times in VSF. The results provided key hydraulic parameters for bighead carp movement in VSFs, which can serve as reference design for the future VSF and others fishway designs for this species.