Understanding the impact of human sounds on eel behaviour, a way to develop behavioural guidance techniques

Abstract

The use of sound as a fisheries management tool is a growing area of research. A large amount of interest has been directed towards the use of ultrasound as a means of deterring clupeid and salmonid fish from hazardous areas and guiding them towards safer alternative routes. Infrasound has been used also in an attempt to deter other species, such as the European eel (Anguilla anguilla).
The aim of this study was to investigate the potential use of sound to manipulate fish behaviour in order to mitigate the impacts of man-made structures. Attempts were made to deter, attract, or elicit other behavioural responses in two migrating species, the European eel and the River lamprey (Lampetra fluviatilis). Various sound intensities and frequencies were investigated under different experimental settings. Individuals were exposed to tones of incrementally changing frequency, at various sound levels, in single tanks while their behaviours were recorded. This allowed us to study the response of the two species to sounds of different frequencies at different levels.
In order to see if these findings could be applicable outside of such restricted tank environments, another set of experiments have been conducted in an outdoor re-circulatory flume.
The first experiment consisted of an "Acoustic maze" which presented each fish, one at a time, with a multiple choice of corridors to go through, with some corridors containing far more intense sound fields than others. The aim of this experiment was to observe any bias in favour of either the corridors with sound or the corridors without sound illustrating an attraction or repulsion for the stimulus. A continuous broadband noise including frequencies between 60 and 1000Hz was used as the stimulus.
The second experiment consisted of a setup with a standard vertical bar screen and a bypass channel. In this experiment, a series of three underwater speakers were set up in order to create an area of sound anterior to the screen. The effectiveness of using combined physical and acoustic screens to deflect fish to more benign bypass routes was tested. The same type of stimulus as in the previous experiment was used and another run of trials was done with 100 Hz pulsed tones.
Preliminary results have suggested that sound was having an effect on both species behaviours, although the response varies intra- and interspecifically. In addition, fish have shown significant numbers of repulsions to sound's exposure in both experiments held in the re-circulatory flume.

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Identifiers

ORCID for Timothy Leighton: orcid.org/0000-0002-1649-8750

ORCID for Paul White: orcid.org/0000-0002-4787-8713

ORCID for Paul Kemp: orcid.org/0000-0003-4470-0589

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