Flow hydrodynamics drive effective fish attraction behaviour into slotted fishway entrances

Abstract

Effective shways rely on attracting sh, utilising the natural rheotactic behaviour of sh to orient into an attraction ow near the entrance. Despite the critical importance of attraction, understanding of the hydrodynamics of vertical slot entrances in relation to sh behaviour remains poor. Herein, hydrodynamic measurements of ows at slotted shway entrances were experimented with two different designs, two velocities, three water depths, and two sh species, silver perch (Bidyanus bidyanus) and Australian bass (Percalates novemaculeata). Fish behaviours were tracked in relation to hydrodynamic measures of three-dimensional velocity and turbulent kinetic energy (TKE). There were distinct differences in the attraction ow between entrance designs, irrespective of velocity and water depth. Plain slotted entrance produced a more symmetric ow in the centre of the ume, causing sh to approach the entrance by skirting the core of the attraction jet ow and areas of high turbulence. In contrast, streamlined slotted entrance design resulted in an asymmetric attraction ow which guided sh along the wall of the ume, improving attraction for both species. There were clear patterns in swimming trajectories for silver perch, swimming along the sidewalls of the observation zone towards the entrance, but Australian bass were less predictable, using random routes on their way to the slotted entrance. Both species preferred areas of low turbulence (TKE < 0.02 m 2 /s 2 ) and the asymmetric attraction ow along one of the sidewalls created by the streamlined entrance improved the sh attraction. This work has important implications for design of vertical slotted entrance systems.

An Open-Source Cross-Section Tool for Hydrodynamic Model Geometric Input Development

“…In oceans, hydrodynamic models can be used to help characterize the tides [1] and to simulate regional oceanic circulation [2]. In estuaries, hydrodynamic model results can be used to simulate shallow water wave motions [3,4], to simulate flooding [5], as input to water quality models, for purposes including water project operation [6], and as input to particle tracking models [7], for purposes including determining the effects of water project operations on fish survival rates [8][9][10]. In riverine systems, hydrodynamic modeling can be used to better understand flood risks [11] and to evaluate the effects of dredging [12].…”