Behavioural changes in small-spotted catshark (Scyliorhinus canicula) exposed to shipping and biological sounds in aquarium

In this study, we exposed twelve specimens of small-spotted catshark (Scyliorhinus canicula) to biological and anthropogenic sounds in order to assess their behavioural changes potentially referable to pray presence and masking effect due to the shipping noise. Specifically, the sharks held individually in aquarium were exposed to four acoustic experimental conditions differentiated in their spectral (Hz) components (biological and anthropogenic mixed sources) and intensity (dB re 1 μPa) levels. Swimming behaviour and spatial distribution of the specimens were recorded. The results highlighted significant differences in time spent in swimming and in spatial use of the aquarium among the experimental conditions. The sharks concentrated their swimming behaviour in the aquarium’s lower sections when the intensity levels of the biological acoustic sources were higher than the anthropogenic ones. Conversely, when the intensity levels of the anthropogenic sources were higher than the biological, the specimens showed the highest values of time spent in swimming. In conclusion, this study hypothesised that the environmental soundscape could play an important role in the catshark prey-predator relationship and that the impact of masking effect can depend on the acoustic intensity levels.