Interannual variation in Brown Skua foraging areas and assessment of spatial interaction with trawl fisheries in coastal Patagonia, Argentina.

SUÁREZ, NICOLÁS; IBARRA, CYNTHIA; YORIO, PABLO

Congreso; World Seabird Conference; 2021

Skuas are scavengers in both marine and terrestrial environments, feeding on a variety of prey types and taking advantage of fishery discards. Little is known on the trophic ecology of the Brown Skua (Catharacta antarctica) breeding along the Patagonian coast, Argentina. To assess the interannual variation in the use of feeding areas during the incubation period and the possible spatial interaction with coastal trawl fisheries, a total of 24 global positioning system loggers were deployed on adults during the 2016 to 2018 breeding seasons. Skuas foraged mostly in open waters in the three study years. During 2016, birds travelled east of the colony (mean = 87.4º), reaching a maximum distance from the colony of 32.8 km (0.9-56.8; n = 10 birds and 124 trips) and covering over 1670 km2. During 2017 and 2018, birds travelled mainly northeast (38.7º and 37.9º, respectively) up to 61.2 km (1.1-109.52; n = 8 birds and xx trips) and 48.7 km (1.3-97.48; n = 6 birds and xx trips) from the colony, respectively. In both years birds used a larger total area than in 2016 (3094 and 3727 km2, respectively). During 2017 and 2018, tracked individuals used 70 and 81% of the area used in 2016, respectively. The operation of the coastal trawl fishery based in Rawson port, which consisted of 40 vessels, showed no overlap with foraging skuas in the three years, as changes in market demands and target species resulted in the northward movement of fishing activity. These results show a similar use of marine environments between years and the importance of waters surrounding the colony in the trophic ecology of the species. Results also suggest the need for further studies to assess the interaction between Brown Skuas and trawl fisheries, given the potential changes in the spatial pattern of fishing activity.