ECOLOGY, ECONOMY AND ETHICS: HOW TO CREATE HARMONY BETWEEN FISHERS AND COMMON BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS, MONTAGU 1821) IN THE NORTHERN TYRRHENIAN SEA

This PhD project (2021–2023), co-financed by the University of Siena and the Life DELFI project (LIFE 18 NAT/IT/000942), aimed to reduce negative interactions between small-scale fisheries and the common bottlenose dolphin (Tursiops truncatus). The study focused on using interactive acoustic deterrent devices (pingers) to minimize entanglement risks, bycatch, and economic losses for artisanal fishers. The research tested the DiD01 pinger (5–500 kHz, 168 dB 1 µPa at 1 m), developed by STM S.r.l., in the Northern Tyrrhenian Sea (southern Tuscany). An initial survey of 35 fishers identified 18 using fixed gillnets, with 83.33% reporting dolphin interactions, leading to an estimated economic loss of €4,800 ± €3,392.80 annually. About 77.78% were interested in testing mitigation measures. Over three years, 25 fishers from 20 vessels participated in trials across five areas: Porto Santo Stefano, Talamone, Marina di Grosseto, Piombino, and Porto Ercole (added in 2022). The study compared nets with (TEST) and without (CTRL) pingers across 868 fishing trials (573 TEST, 295 CTRL) from March 2021 to November 2023. It assessed species richness, catch per unit effort by weight (CPUEW), and pinger effectiveness in reducing damage. A total of 83 species were caught, with cuttlefish, red mullet, caramote prawn, and spottail mantis shrimp being most frequent. Species richness was higher in TEST nets, indicating reduced dolphin presence improved target species diversity. Statistical analysis showed CPUEW differences were significant in 2023, being higher in 2022–2023 (p<0.05), lower in winter vs. autumn, in northern vs. southern areas, and in deeper vs. shallower waters, but not significantly affected by dolphin interactions (p>0.05). Pingers reduced haul damage by 25.73% and net damage by 29.52%, leading to a 28% drop in harmful dolphin interactions and average annual savings of €1,924.33 ± €679.07. No dolphin bycatch occurred, though two stranded specimens showed signs of fishery interactions. An ex post survey of 18 fishers revealed 83.31% satisfaction with pingers, though 50% suggested technical improvements. Additionally, 66.67% expressed interest in alternative economic activities such as “pescaturismo” (tourist fishing).