Drivers of negative phonotaxis for common carp (Cyprinus carpio) in response to resonant insonified bubble curtains

Abstract

This thesis investigates the potential for insonified bubble curtains that use the resonant properties of bubbles to be used as behavioural deterrents for fish. This can help mitigate the ecological impacts of river and estuarine infrastructure such as hydropower technologies. To this end, in a series of four flume experiments, the following was tested: (1) the reactions of fish to a low air flow bubble curtain; (2) the effect of deconvoluting visual cues from stimuli generated by the bubble curtain; (3) the effectiveness of resonant versus non-resonant insonified bubble curtains to deter passage, determining the stimuli responsible for eliciting deterrence; (4) the question of whether regions with different levels of particle motion or acoustic pressure influence fish behaviour. Models of the extinction cross-section for each bubble population were used to explain the acoustical effects, confirming bubble resonance. Results of this fundamental study showed that bubble clouds with a higher proportion of resonant bubbles were better at deterring fish passage and this was likely influenced by multimodal cues, specifically, particle displacement, and sound pressure within a body length of the fish. All insonified bubble curtains were less effective in the presence of visual cues, likely because when available these are given greater importance by fish over mechanosensory cues. The benefits of energy-efficient, resonance-based acoustic behavioural deterrents examined by this thesis may be explored further for field-based applications. Finally, the importance of avoiding certain historical pitfalls when characterising acoustically active bubble curtains is discussed.

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Identifiers

ORCID for Nicholas Flores Martin: orcid.org/0000-0003-1131-2934

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

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