Abstract
Human noise pollution has increased markedly since the start of industrialization and there is international concern about how this may impact wildlife. Here we determined whether real motorboat noise affected the behavior, space use and escape response of a juvenile damselfish (Pomacentrus wardi) in the wild, and explored whether fish respond effectively to chemical and visual threats in the presence of two common types of motorboat noise. Noise from 30 hp 2-stroke outboard motors reduced boldness and activity of fish on habitat patches compared to ambient reef-sound controls. Fish also no longer responded to alarm odours with an antipredator response, instead increasing activity and space use, and fewer fish responded appropriately to a looming threat. In contrast, while there was a minor influence of noise from a 30 hp 4-stroke outboard on space use, there was no influence on their ability to respond to alarm odours, and no impact on their escape response. Evidence suggests that anthropogenic noise impacts the way juvenile fish assess risk, which will reduce individual fitness and survival, however, not all engine types cause major effects. This finding may give managers options by which they can reduce the impact of motorboat noise on inshore fish communities.
Highlights
Sound is a fundamentally important sensory cue for marine organisms[1], but in most inshore waters the natural soundscape generated by biological and physical sources is polluted by anthropogenic noise[2,3]
Little is known of how the alteration of natural soundscapes by anthropogenic noise influences the information-base upon which behavioural decisions are made
Many studies have found that anthropogenic noise affects communication, movement patterns and foraging[2,9,50,51], but it is often difficult to link these effects to individual fitness or population-level repercussions[24]
Summary
Sound is a fundamentally important sensory cue for marine organisms[1], but in most inshore waters the natural soundscape generated by biological and physical sources is polluted by anthropogenic noise[2,3]. Noise that alters the ability of fishes to get information through sound, or disrupts the auditory system, may have ecological consequences for each part of a fish’s lifecycle While these have been explored to a limited extent using noise playback in laboratory conditions, we know little of the effect of anthropogenic noise on marine organisms within a natural setting. Most marine organisms have complex life cycles, where embryos develop into dispersive larvae that metamorphose and settle to join the juvenile and/or adult population It is during this transitional stage between environments when anthropogenic noise can have a strong influence on survivorship and cohort success[19,24,25]. Anything that alters the ability of an organism to use sensory information to assess or judge risk will modify their behavioural decisions and probability of death[2,21,28]
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