The soundscape of a mussel farm: Biophony and man-made noise levels

peer reviewedDuring the summer of 2015, four Passive Acoustic Monitoring (PAM) surveys were carried out over a mussel farm in the Venetian (Italy) littoral zone at night-time hours. A qualitative and quantitative analysis of the soundscape was carried out. The high frequencies component of the soundscape (i.e above 2 kHz) was dominated by snapping shrimps sounds, while the low frequency component (i.e. below 2 kHz) was characterized by fish vocalization, mainly emitted by Sciaena umbra (Sciaenidae), with less frequent occurrences emitted by Gobidae spp. S. umbra highest vocal activity was recorded from June to August inside the mussel farm. The low frequency component of the soundscape was dominated by boat noise; in particular, low frequency noise (i.e. below 4 kHz) emitted by commercial ships and passenger cruises. The Acoustic Complexity Index (ACI) was found to increase concurrently with the number of S. umbra vocalizations: ACI highest values corresponded with S. umbra chorus recorded during July. The results of this study suggest that the mussel farm may function as a Fishery Aggregated Device (FAD), where fish might utilize it for different ecosystem services. Despite this, man-made noise was present in most of the acoustic samples, suggesting a potential impact on the local faun