Reactions of temperate reef fish larvae to boat sound

Abstract

ABSTRACT1. Anthropogenic sound as a stressor in aquatic systems is of increasing concern. The present study evaluated whether boat sound either deters larval fish or interferes with their ability to use biological sounds for navigating.2. Pre-metamorphic larval fishes were caught in a pair of light traps deployed off a shallow rocky reef in Port Phillip Bay, Australia, with one trap randomly assigned one of two boat sound treatments, at sound pressure levels experienced in situ, and the other without any sound treatment.3. The boat sound treatment included either (1) boat engine sound without any other sound, or (2) boat engine sound with biological and physical sound from a pier, a positive but weak cue indicative of much of the available benthic habitat in the vicinity.4. Total larval abundance and species composition of the assemblage were compared between the sound-exposed trap and the control trap. When only boat sound was broadcast, no significant differences between sound-exposed and control traps was observed. When boat sound was broadcast together with pier sound, significantly more fishes were caught in the sound-exposed trap (~300% of 'control' traps).5. The results of this study suggest that a) common boat sound is not readily avoided by larval fishes, and that b) larval fishes are attracted to biological sound in spite of the presence of boat sound. Together the results suggest that boat sound at levels experienced in situ might not have deleterious effects on recruitment of larval fishes, i.e. the capacity to alter recruitment patterns.

Boat noise disrupts orientation behaviour in a coral reef fish

“…Boat noise was not consistently avoided during our study, which is also in line with the recent result of Jung & Swearer (2011), who noted that boat noise played alone did not reduce the number of fish caught in light traps when compared with traps playing no sound. The lack of a significant effect of boat noise played with ocean noise could be because there is no baseline directional response in Apogon doryssa to ocean noise that could be interrupted, because they had already experienced boat noise in the ocean and become conditioned to this sound (Simpson et al 2010), or because boat noise in the ocean does not represent a threat that necessitates a behavioural response.…”

“…Sample sizes are given in parentheses. Asterisks show the p-values of chisquared tests for the comparisons of distributions indicated by the associated bars: *p < 0.05, ***p < 0.001 (Jung & Swearer 2011). However, the greatest observable differences in our choice chamber experiment were the proportions of fish swimming away from the playback and choosing the middle section; this would not have been observable in a light trap experiment, where only positive responses can be recorded.…”

“…Brandt et al 2011, Rodkin et al 2012. However, the lower intensity noise from boats, which is ubiquitous in populated coastal areas, is often ignored (although for exceptions see Picciulin et al 2010, Jung & Swearer 2011, Bracciali et al 2012. This source of noise has the potential for extensive effects and is likely to be especially damaging where human populations overlap with sensitive habitats where high numbers of endemic and rare species use sound, such as on coral reefs.…”

Signals and noise in the octavolateralis systems: What is the impact of human activities on fish sensory function?

“…In controlled experiments, however, it is not always the case that animals react to such noise sources adaptively. For instance, boat noise does not repel larval fish in a 2‐trap experiment (Jung & Swearer ). Boat noise alone is neither attractive nor repellent (equal trapping).…”

“…The use of reef sounds may remain behaviorally robust even in the face of anthropogenic pollution. Jung and Swearer () show that larvae were significantly attracted to a trap broadcasting reef plus boat sounds, despite the fact that the recorded reef was degraded (low biotic contribution to the sound) and the presence of boat noise was a potential masker.…”