Dolphins and coastal fisheries within a marine protected area: mismatch between dolphin occurrence and reported depredation

1. Dolphins are often blamed for reducing fisheries catches and may be killed in retaliation. Depredation of fishing gear in coastal Mediterranean waters is normally caused by bottlenose dolphins. Economic impact, however, may be modest even within areas of reportedly acute conflict. 2. Boat surveys and interviews were conducted to investigate dolphin occurrence and interactions with fisheries within the 167km(2) Porto Cesareo Marine Protected Area (MPA) in southern Italy. Based on 69 interviews with fishermen using bottom-set trammel and gill nets, there was reportedly a high occurrence of depredation by bottlenose dolphins. Depredation was reported by 92% of the fishermen operating in or near the MPA, and 67% of them claimed an economic cost in excess of (sic)1000 per year, with a mean reported cost of (sic)2561: a higher impact than in other Mediterranean studies. 3. According to local fishermen, dolphin occurrence and depredation peaked in spring and autumn, coincident with the study's surveys at sea. Dedicated visual surveys totalling 1255km of effort, however, resulted in no encounters with cetaceans. Information from interviews and boat surveys was therefore contradictory, suggesting that reports of acute depredation do not imply a constant presence of dolphins within the MPA. 4. While depredation in the MPA might be caused by wide-ranging dolphins or incursions occurring overnight, damage may well be overestimated or over-reported. As local fishermen had previously benefited from subsidies, interviews made during this study could be perceived by some as an opportunity to influence future decision-making regarding monetary compensation for the impact of depredation. 5. Evidence from interviews also indicated that species and factors other than dolphins were responsible for part of the damage. Copyright (C) 2011 John Wiley & Sons, Ltd.