18 May 2011

Bottlenose dolphin depredation in Sardinia

Perhaps as a consequence of prey scarcity caused by overfishing, in some Mediterranean Sea areas coastal communities of bottlenose dolphins have specialised in the depredation of fishing nets. While the problem is relatively widespread, it is particularly acute within a Marine Protected Area in western Sardinia, Italy, where angry fishermen blame dolphins for damaging gear and reducing landings.

A preliminary study conducted in February 2011, based on approximately 100 interviews to artisanal fishermen, helped define the magnitude of the conflict. In this area, the mean economic damage perceived by local fishermen (€8,500 boat/year) is the highest reported so far throughout the Mediterranean region. Several fishermen are now selling their boats as a consequence of unsustainable depredation suffered in recent years, while others advocate the use of acoustic harassment devices or threaten to kill the dolphins. Furthermore, depredation of fishing gear results in significant entanglement and incidental mortality, threatening a dolphin population classified as Vulnerable in the IUCN Red List.

Contrary to the findings in Apulia, Italy, boat surveys in Sardinia confirmed a high occurrence of bottlenose dolphins, and reports by the local fishermen appeared credible. However, the actual economic damage remains to be documented, as figures above refer to the perceived damage alone.

Lessons learned in our study were disseminated through a workshop with fishermen and local authorities, as well as through a comprehensive report to the MPA management and a digital photo book, with the goal of informing conservation management.

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