Long-term study of the at-sea distribution of seabirds and marine mammals in the Scotia Sea, Antarctica

This paper presents the results of at-sea monitoring of seabirds and cetaceans over five summer seasons, 2010 to 2014, at the Scotia Sea, Antarctica, covering a total of 1463 nautical miles with 1100 ten-min counts. Among birds, six species of Procellariiformes were abundant: Black-browed Albatross, Cape petrel, Southern Fulmar petrel, Antarctic Prion, Wilson’s Storm petrel, and Black-bellied Storm Petrel. Antarctic Prion was the dominant species within the 5 years whereas Cape petrel showed successive decreases in abundance. Five baleen whales where recorded: Humpback, Sei, Southern Right, Fin and Minke, which had different abundances during our study. Fin whale had the highest mean encounter rate in the five years (0.29 ± 1.57 whale/nautical mile), followed by Humpback whale (0.09 ± 0.54). Annual dissimilarity in abundance of both birds and cetaceans occurred in conjunction with changes in sea surface temperature and ice cover, showing the dependence of top predators to environmental changes. The largest aggregations of all top predators (seabirds and cetaceans) were recorded mainly in two regions: west and south of South Orkney Is., suggesting important prey availability, especially krill, in those areas.