Spatial distribution of zebrafish (Danio rerio) as a behavioral index of stress in response to sound

Anthropogenic sounds are emitted from different origins in the natural environments in various time and space domains. These sounds may directly or indirectly affect physiology and behaviour of animals. Sound related spatial distribution changes can be used as an indicator to assess stress related behaviour in aquatic animals. For this purpose, the experiment was designed to investigate the effect of temporal variation of sound exposed zebrafish (Danio rerio) spatial distribution as a behavioural indicator of stress expression. The results showed that sound affected the spatial distribution pattern of zebrafish in such a way that in the brief time span, the fish in continuous (CS), regular intermittent (1:1) and regular intermittent (1:4) tend to spend more time in the lower layer of the tank. Also, in the prolonged time span, fish in all sound treatments irrespective to the temporal pattern tend to spend more time in the lower layer of the tank. Moreover, in the brief time span, there was a significant difference in horizontal displacement in the tank (distance from the sound source) when fish exposed to irregular intermittent (1:1-7) treatment (P<0.01). Also, there were significant differences in horizontal displacement in the tank when fish exposed to irregular intermittent (1:1-7) and continuous (CS) treatments (P<0.05). Further studies are needed to investigate the effects of anthropogenic sounds on both predator and prey and their interactions.