Behavioral changes in response to sound exposure and no spatial avoidance of noisy conditions in captive zebrafish

Abstract

Auditory sensitivity in fish serves various important functions, but also makes fish susceptible to noise pollution. Human-generated sounds may affect behavioral patterns of fish, both in natural conditions and in captivity. Fish are often kept for consumption in aquaculture, on display in zoos and hobby aquaria, and for medical sciences in research facilities, but little is known about the impact of ambient sounds in fish tanks. In this study, we conducted two indoor exposure experiments with zebrafish (Danio rerio). The first experiment demonstrated that exposure to moderate sound levels (112 dB re 1 μPa) can affect the swimming behavior of fish by changing group cohesion, swimming speed and swimming height. Effects were brief for both continuous and intermittent noise treatments. In the second experiment, fish could influence exposure to higher sound levels by swimming freely between an artificially noisy fish tank (120–140 dB re 1 μPa) and another with ambient noise levels (89 dB re 1 μPa). Despite initial startle responses, and a brief period in which many individuals in the noisy tank dived down to the bottom, there was no spatial avoidance or noise-dependent tank preference at all. The frequent exchange rate of about 60 fish passages per hour between tanks was not affected by continuous or intermittent exposures. In conclusion, small groups of captive zebrafish were able to detect sounds already at relatively low sound levels and adjust their behavior to it. Relatively high sound levels were at least at the on-set disturbing, but did not lead to spatial avoidance. Further research is needed to show whether zebrafish are not able to avoid noisy areas or just not bothered. Quantitatively, these data are not directly applicable to other fish species or other fish tanks, but they do indicate that sound exposure may affect fish behavior in any captive condition.

The effect of temporal variation in sound exposure on swimming and foraging behaviour of captive zebrafish

“…However, upward swimming responses may also suggest that the onset of sounds from experimental exposure draws attention and may induce explorative behaviour (cf. Neo et al, 2015). However, as we did not confirm this effect in the current data set, the intermittent treatments here might actually have been responsible for the fish missing the initial cue for the introduction of water fleas to the water.…”

“…In addition, sound exposure not only affected response latency to the water flea introduction and foraging efficiency, but also altered their swimming behaviour immediately after the onset of the sound exposure (cf. Neo et al, 2015). This behavioural change, which was true for relatively brief increases in swimming speed during two of the intermittent sound treatments, probably reflects the startle responses in the initial period of exposure.…”

“…Zebrafish showed only a brief startle response with the onset of the sound playbacks and did not show any sign of anxiety or unusual swimming behaviours in their holding tanks after the experiments (cf. Neo et al, 2015). All housing and experimental conditions were in accordance with the ASAB/ABS guidelines.…”

“…In the experimental studies on fish (Purser & Radford, 2011;Voellmy et al, 2014), it was assumed but not investigated that the effect of sound on foraging efficiency was caused by an impact on the predator and not on the prey and the relevance of temporal variation in sound characteristics (cf. Neo et al, 2015;Neo et al, 2014) remained unexplored.…”

“…Cachat et al, 2010;Egan et al, 2009;Gaikwad et al, 2011;Gerlai, Lee, & Blaser, 2006) and to tackle questions of the impact of sound on predatoreprey interactions in particular. Neo et al (2015) exposed adult zebrafish to different sound patterns and showed initial startle responses, relatively brief anxiety-related response behaviours, but no longer-lasting effects or spatial avoidance. They reported sound exposure-related changes in swimming speed and group coherence, while fish moved upwards in response to moderate sound levels (112 dB re 1 mPa) and downwards (for brief periods) in response to higher sound levels (120e140 dB re 1 mPa).…”