Structure of the Cetacean Community Around the Antarctic Peninsula

Abstract

e aim of the present study was to investigate if cetacean diversity varies among areas with di erent oceanographic conditions around the Antarctic Peninsula. e study area consisted of the Drake Passage, Brans eld and Gerlache Straits and the Weddell Sea. is region has a complex circulation pattern, including mesoscale jets and eddies, which together with dimensions of shallows and canyons in bays, ords and straits make the complexity of current elds. ese characteristics play an important role in the transportation, concentration and retention of nutrients, favoring primary and secondary productivity and attracting the top consumers. e area was divided into 10 sub-areas based on oceanographic features such as surface circulation patterns. Cetacean distribution data were obtained during ship-based surveys run by the Brazilian Antarctic Program from 1998 to 2011 austral summers. Line transect sampling methods were used to calculate cetacean encounter rates. e diversity index for each area was determined by the Shannon-Weaver diversity index. Humpback, minke and killer whales were the most frequently sighted species, predominating in areas with low species richness such as Gerlache Strait. Areas without species dominance (e.g. Elephant Island and Weddell Sea) showed greater diversity. Our results suggest that open areas and areas close to oceanographic fronts sustain lower encounter rates for individual species but support greater diversity than con ned areas.