Hydrokinetic Turbine Effects on Fish Swimming Behaviour

Hydrokinetic turbines, targeting the kinetic energy of fast-flowing currents, are under development with some turbinesalready deployed at ocean sites around the world. It remains virtually unknown as to how these technologies affectfish, and rotor collisions have been postulated as a major concern. In this study the effects of a vertical axishydrokinetic rotor with rotational speeds up to 70 rpm were tested on the swimming patterns of naturally occurringfish in a subtropical tidal channel. Fish movements were recorded with and without the rotor in place. Results showedthat no fish collided with the rotor and only a few specimens passed through rotor blades. Overall, fish reduced theirmovements through the area when the rotor was present. This deterrent effect on fish increased with current speed.Fish that passed the rotor avoided the near-field, about 0.3 m from the rotor for benthic reef fish. Large predatory fishwere particularly cautious of the rotor and never moved closer than 1.7 m in current speeds above 0.6 ms-1. Theeffects of the rotor differed among taxa and feeding guilds and it is suggested that fish boldness and body shapeinfluenced responses. In conclusion, the tested hydrokinetic turbine rotor proved non-hazardous to fish during theinvestigated conditions. However, the results indicate that arrays comprising multiple turbines may restrict fishmovements, particularly for large species, with possible effects on habitat connectivity if migration routes areexploited. Arrays of the investigated turbine type and comparable systems should therefore be designed with gaps ofseveral metres width to allow large fish to pass through. In combination with further research the insights from thisstudy can be used for guiding the design of hydrokinetic turbine arrays where needed, so preventing ecologicalimpacts