M. F. Blasi • F. Roscioni • D. Mattei
Abstract Traditional fish aggregating devices (FADs) have long been used throughout the Mediterranean Sea, but few data are available on their interactions with Loggerhead Turtles (Caretta caretta). In this study, we examined the influence of FADs on the spatial and seasonal distribution of Loggerhead Turtles in the Aeolian Archipelago (Italy) as well as the pattern of bycatch and other FAD-related impacts. We implemented an overlap analysis between FAD locations and the distribution of Loggerhead Turtles per season. We found that the geomorphology of the volcanic islands significantly influenced the selection of foraging hotspots. However, during the fishing season, the turtles strongly interacted with FADs, moving from neritic to oceanic habitats. Specifically, during the fishing season, we found 1) a higher number of turtles, 2) a clear overlap between Loggerhead Turtle and FAD locations and 3) shorter distances between turtles. Turtle-FAD interaction occurred in all life stages, although bycatch was more frequent for smaller turtles. FADs also affected the distribution of turtles across years by habituating them to temporary and unnaturally aggregated food sources. We found high levels of bycatch in FADs (19.4%), especially for turtles already entangled in longlines (33%). FADs were potentially dangerous because the turtles became entangled in the anchoring lines of nylon, which wrapped around their necks, flippers and posterior limbs. We suggest further investigations to assess the influence such illegal devices pose on the foraging ecology of Loggerhead Turtles and the levels of bycatch in other Mediterranean areas.