Interactions between air-breathing marine megafauna and artisanal fisheries in Southern Iberian Atlantic waters : results from an interview survey to fishers

Abstract

The coastal waters off Western Iberia are an important fishing ground and a marine megafauna foraging area. Overlap between fishery target species and the diet of several air breathing marine megafauna species can lead to negative interactions and consequently conservation and economic issues. This work aimed to assess marine megafauna (cetaceans, marine birds, and marine turtles) – fishery interactions through face-to-face interviews to fishers of the local and coastal artisanal fisheries fleets in the landing sites of the Portuguese mainland Southern coast (Algarve). The main goal was to identify and evaluate problematic interactions known to cause bycatch or economic loss through depredation. We found that bycatch is a concern for all marine megafauna groups, but depredation problems are mostly associated with cetaceans. Of the sampled artisanal fisheries (longlines, pots and traps, bottom set-nets, and purse seine), the fishing gears of most concern were purse seine and coastal bottom set-nets. Purse seine showed problems associated with important bycatch numbers, especially of common dolphins, Delphinus delphis, while bottom set-nets have considerable bycatch of all animal groups and depredation was highly associated with bottlenose dolphins, Tursiops truncatus. Bycatch and depredation were found to be species, gear, area, and vessel size dependent. Economic loss caused by depredation led to catch and gear damage and was widely reported by bottom set-net fishers, ranging from 7% to 21% of their revenue. Higher losses were reported for local vessels in leeward (eastern) Algarve area. This study showed that the active participation of fishers provides improved localized knowledge on interactions between local and coastal fisheries and marine megafauna, allowing for the definition of specific management and mitigation strategies.