Programma della conferenza

The interaction between small-scale fisheries and dolphins has always been contentious and often results in conflicts between fishermen and dolphins with important losses from both sides. These interactions could also often result in the entanglement of marine mammals in fishing gear, the major cause of mortality in marine mammals by human activities. The Tursionet project, funded by the Pelagos Initiative, aims to study the interactions and relationship between different types of fishing gear and the population of bottlenose dolphins that inhabit the coastal waters in the Pelagos Sanctuary, a Marine Protected Area for marine mammals located in the Northwestern Mediterranean between France, Italy, and Monaco. Several hydrophones have been deployed along the Ligurian coast near different types of fishing gear such as gillnets and pots in continuous recording to monitor the acoustic interactions of dolphins passing nearby. The frequency of encounters, the types of vocalizations, and the diel pattern are investigated to assess the intensity of these interactions and further explore the impacts they may have on the local population of dolphins. The different sites will also show if there are particular hotspots of activity where further monitoring may be needed. Finally, the results from this project will result in the development of automated systems that will be used in monitoring these interactions and ultimately develop mitigation strategies to reduce conflicts between the local fisheries and dolphins.

The soundscape is the acoustic environment resulting from natural and human sounds present within an ecosystem or an area. It acoustically profiles the location as a whole, comprising the fingerprint of the soniferous species using the area (biophonies), the noisy human activities (anthropophonies) and the physical phenomena (geophonies). As such, the study of the acoustic patterns and the spectral characteristics of the different components of the soundscape can be viewed as an ecological metric of the status, dynamics and health of an ecosystem, and an indicator of environmental changes.

This study aims to provide baseline information on the biophonic component of the underwater soundscape of the Marine Protected Area "Secche di Tor Paterno" (Mediterranean Sea), investigating site-specific diversity and temporal patterns in sounds’ production. Using autonomous recorders released/recovered in the MPA, 24-days acoustic data were collected in the summer 2020, 2022 and 2023. A total of 6.741 files corresponding to 113 hours of recordings was analysed using Raven Pro, Rx and Avisoft Pro software.

Biophonies were detected at all times. At least 8 categories of fish sounds were recognized, indicating the positive acoustic presence of Scorpaena spp., Sciaena umbra and the cryptic Ophidion spp. Bray-call series emitted by bottlenose dolphins (Tursiops truncatus) and impulsive sounds produced by Alpheidae species (i.e. snapping shrimps) were discriminated as well. The monthly/daily patterns revealed that fishes were acoustically active during the night, while crustaceans all-day-long, with two significant activity peaks (sunrise and sunset). The intense, concomitant nocturnal sound production by different fish species – mainly related to reproduction – was affected by the noise generated by vessels crossing the MPA, with a reduction of the emission rates.

These early findings emphasize the importance of soundscape studies to understand the acoustic community of a site, detect its changes/alterations, and improve MPA conservation effectiveness.