Impacts of anthropogenic sound on fish behaviour

Abstract

Species like the European eel (Anguilla anguilla) and the river lamprey (Lampetra fluviatilis), as a consequence of their migratory life cycle, are more likely to experience several of anthropogenic pressures (e.g. infrastructures, pollution, barriers to migration). Both species populations have been severely declining for several decades, leading international organizations to institute some strict protective regulations. To meet the expectations of these regulations, there is a current need to investigate further the anthropogenic impacts responsible for this decline and to develop new methods to ensure the protection of these species. In addition, there is scientific concern about the rising underwater sound levels due to human activity and its consequences on marine and freshwater life. This thesis investigated the effects of basic anthropogenic sounds on the behaviours of European eel and river lamprey. Furthermore, this research also looked into re-using the previous findings to improve current knowledge in behavioural mitigation techniques for fish passage at infrastructures. Hearing capabilities of both species and their responses to acoustics were assessed using two approaches: (1) a confined experiment using specific test frequencies and allowing the establishment of a detailed panel of behaviour, (2) a novel approach involving an acoustic maze set in a large flume, to observe sounds impacts on fish movements. Finally, a third experiment involving a traditional mitigation system (bar-screen), tested the efficiency of this system in combination to two acoustic stimuli. In terms of hearing capabilities, both species appeared to be more sensitive to low-frequency sounds. Fish swimming trajectories were poorly affected by sound. Nevertheless, the time taken by fish to pass the acoustic area was modified by the presence of the acoustic stimuli compared to control conditions. A rejection behaviour was observed with several fish in presence of sound. Furthermore, our results indicate that the response is very dependent of the test subject. This research brought new material and methodology for the study of behavioural response of fish to sound. Nevertheless, more work is needed to develop a more effective acoustic signal to achieve better guidance of anguilliform species at infrastructure passage and also to determine long term effect of sound on fish.

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Identifiers

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

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

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

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