Use of acoustics to enhance the efficiency of physical screens designed to protect downstream moving European eel ( Anguilla anguilla )

Abstract

European eel, Anguilla anguilla (L.), is vulnerable to entrainment at a variety of man‐made intakes, including those that lead to hydropower turbines or other abstraction points. Two experiments were conducted to investigate the potential for acoustic stimuli to improve the efficiency of a vertical bar screen to guide downstream moving eel. Three underwater speakers were installed along the channel wall of an external flume, upstream of the screen. In the first experiment (a), screen guidance efficiency recorded in the presence (treatment) and absence (control) of a continuous broadband stimulus was individually compared between fish from two respective groups. Adopting a “before‐after” design, the second experiment (b) assessed individually the guidance of control eels from the group previously used in experiment 1 when exposed to a 100 Hz pulse. The majority of eels reached the bypass in both experiments with only three passing through the screen during the controls against one during each acoustic treatment. Rejection of the area adjacent to the speakers was more common during the acoustic treatment, with eels moving past the speakers more rapidly in the presence of sound. The results suggest that employing acoustic stimuli enhances the guidance efficiency of physical screens.

Bibliographic Information