Depredation by marine mammals in fishing gear

Book excerpt: Marine mammal depredation refers to the phenomenon of marine mammals partially or completely removing catch from fishing gear. Its results, which can affect the survival of wild dolphin populations, as well as damage gear or target fish, disturb fishing activities and generate economic losses for fishers, are a growing cause for concern in several Mediterranean and Black Sea fisheries. Depredation events often leave dolphins injured or snared in fishing nets and fishers with damaged nets and lower catch values. As a result, these interactions can create conflicts between dolphins and fishers, undermining efforts to improve the sustainability of fisheries and the conservation of vulnerable species. This review offers an overview of historical and current trends of depredation by marine mammals in the region, including information on the contiguous Atlantic area west of Gibraltar. The publication aims to assess and synthesize depredation records and describe ongoing projects on depredation in order to improve knowledge on key aspects of depredation, such as the fishing practices associated with depredation events, the economic fallout caused by marine mammal–fisheries interactions and the species and populations most involved in depredation. In the Mediterranean and the Black Sea, coastal fisheries often come into contact with cetaceans, especially bottlenose dolphins (Tursiops truncatus), common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena relicta). These species feature most prominently in the depredation records assessed and are the main research focuses of ongoing monitoring projects in the region. However, Mediterranean monk seals (Monachus monachus) are also responsible for depredation, especially in the eastern Mediterranean, and are the subject of their own short chapter in this review.