Recreational boating represents a primary source of underwater noise in coastal regions; its impacts on fish acoustic communities within Posidonia oceanica meadows, has a gap in knowledge. In the present study, passive acoustic monitoring (PAM) was used to evaluate how boat traffic influences fish biophony across two Mediterranean Marine Protected Areas (MPAs): Capo Gallo–Isola delle Femmine and Capo Caccia–Isola Piana. Data were collected from 16 sites, during the low and high tourist seasons of 2024. To assess the effects of boat disturbance on community-level biophony, generalized linear mixed models (GLMMs) were employed, using acoustic abundance and richness as response variables, while accounting for spatial and temporal factors (MPA and tourist season). Furthermore, individual-level responses were evaluated by analysing shifts in the acoustic features of Sciaena umbra and Scorpaena spp. sounds using generalized linear models.

Results indicate that the increasing of boat presence, from the low to the high tourist season, significantly reduced biophony in terms of acoustic abundance and richness. Moreover, findings show how boat traffic alters acoustics features of the fish signals: in S. umbra, peak frequency, bandwidth, and duration increased; conversely, in Scorpaena spp., bandwidth and duration increased while peak frequency decreased. Results highlight that recreational boating is a pervasive disturb that modify seagrass soundscapes by suppressing biophony and inducing, at individual level, plastic changes in acoustic key ecological functions signals. Also, results suggest that MPA zoning alone is insufficient to protect fish communities from boat noise, demonstrating a critical need for temporal vessel restrictions and the integration of passive acoustic monitoring into conservation management strategies.