Acoustic characteristics of Atlantic salmon feeding behaviour in RAS: Possibilities and pitfalls of using passive acoustics for monitoring in tanks

Summary

Recirculating Aquaculture Systems (RAS) are complex and require continuous monitoring of water quality and system performance. Monitoring of fish behaviour, and particularly feeding activity, can be difficult due to low visibility caused by turbid water and high stocking densities. Passive Acoustic Monitoring (PAM), a non-invasive method based on recording sounds that are present in an environment, could be a valuable monitoring tool in RAS since it is not dependent on visibility. This thesis aimed to improve current knowledge about sound in RAS and explore the possibilities of using PAM to optimise feeding, with the main objective being to determine acoustics characteristics of Atlantic salmon (Salmo salar) behaviour related to feeding in RAS. The results demonstrates that tank soundscapes are affected by feeding activity and feeding regimes (Paper I and II). Feeding events were found to be characterised by sounds of feed pellets hitting the water surface and specific feeding sounds likely associated with pellet capture and/or ingestion (Paper I). In addition, splashes from surface activity and a range of related sounds (Paper I and III) can be found during feeding. Acoustic indices, tailored to be affected by these sounds, revealed that the same feeding regime resulted in similar average soundscape patterns in two different RASs with different designs (Paper I and II). However, they also revealed that system operations can produce sounds masking those of interest and complicate the analysis of the acoustic indices investigated in the current research (Paper I and II). Linking data from system operation can help disentangling the noise sources present in RAS (Paper II). In addition, not all frequency bands are equally sensitive to masking by noise from system operation (Paper I, II, and III), and specific sounds related to surface activity could be used for behavioural monitoring for welfare purposes (Paper III). Combined, the findings of this thesis present possibilities and pitfalls for using PAM in commercial RAS farms and research facilities, for monitoring of both fish behaviour and system performance.

Read publication here:

NVA : hdl.handle.net/11250/5481063