Todd, V.L.G., Todd, I.B.
Acoustic Harassment Devices (AHDs) are used worldwide to deter pinnipeds from predating fish-aquaculture facilities; however, effects on non-target species are of concern. This study focused on the newly developed, Research & Development OTAQ Aquaculture Seal Fence AHD system, tested at a fully operational salmonid farm in Scotland, located within a Special Area of Conservation. The primary aim was to estimate the Source Levels (SLs) of the AHD system in real field conditions and assess its signal propagation. Field measurements revealed that AHD signals were detectable up to 4.2 km away. The estimated SLs ranged from 79.66 to 82.03 dB re 1μPa RMS @ 1 m, which is significantly lower than other commercially available devices; however, despite these low levels, introduction of anthropogenic noise into the marine environment, combined with other sources, should always be considered. This study provides valuable empirical data on the acoustic output of a new AHD system, highlighting its potential to minimise noise pollution compared to existing devices; however, further research is needed to evaluate its efficacy in deterring seals and its impact on non-target species.
