Soundscape in a Northern Patagonian Fjord with Salmon Farms

Resumen: In the Patagonian Fjords (Chile), an explosive development of salmon aquaculture has occurred, making Chile the second largest salmon producer in the world. Several environmental impacts of this industry on marine ecosystems have been identified. However, descriptions of the underwater soundscape near the sea-based salmon installations are scarce. A continuous recording of ~45 h was conducted using a calibrated hydrophone (0.02–60 kHz) anchored at 20 m depth (2 m from bottom) and 250 m from a salmon net pen. Thirteen noises were identified (particle motion metrics were not included). The dominant noise had a peak frequency of ~80 Hz, probably due to electric generators (SPL_RMS ~ 120 dBre1μPa). The second dominant was ~2500 Hz, probably from automatic feeding systems or well boats in use (SPL_RMS ~ 142 dBre1μPa). Outboard motor noises were also present (SPL_RMS ~ 130 dBre1μPa). During only 1 h, anthropogenic noises were absent (SPL_RMS ~ 100 dBre1μPa), where snapping shrimps and fish sounds were found. Therefore, the soundscape was strongly dominated by anthrophony from the salmon net pen with 97% of the total time and ~ 40 dBre1μPa higher than natural sounds. Moreover, the highest noise might be roughly 175 dBre1μPa at 1 m from the net pen (regarding the simple geometric spreading loss model). Consequently, it is raising the necessity to evaluate the effects of these noises on the marine fauna.