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

SUÁREZ, N.; IBARRA, C.; YORIO, P.

Conferencia; 3rd World Seabird Conference; 2021

Skuas are scavengers in both marine andterrestrial environments, feeding on a variety of prey types and takingadvantage of fishery discards. Little is known on the trophic ecology of theBrown Skua (Catharacta antarctica) breeding along the Patagonian coast,Argentina. To assess the interannual variation in the use of feeding areasduring the incubation period and the possible spatial interaction with coastaltrawl fisheries, a total of 24 global positioning system loggers were deployedon adults during the 2016 to 2018 breeding seasons. Skuas foraged mostly inopen waters in the three study years. During 2016, birds travelled east of thecolony (mean = 87.4º), reaching a maximum distance from the colony of 32.8 km(0.9-56.8; n = 10 birds and 108 trips) and covering over 1670 km2. During 2017 and2018, birds travelled mainly northeast (38.7º and 37.9º, respectively) up to61.2 km (1.1-109.52; n = 8 birds and 87 trips) and 48.7 km (1.3-97.48; n = 6birds and 92 trips) from the colony, respectively. In both years birds used alarger total area than in 2016 (3094 and 3727 km2, respectively). During 2017 and2018, 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 thethree years, as changes in market demands and target species resulted in the northwardmovement of fishing activity. These results show a similar use of marineenvironments between years and the importance of waters surrounding the colonyin the trophic ecology of the species. Results also suggest the need forfurther studies to assess the interaction between Brown Skuas and trawlfisheries, given the potential changes in the spatial pattern of fishingactivity.