Netherlands Polar Data Center

Abstract

Helicopter and shipboard surveys were conducted for cetaceans in the Weddell Sea from the German research vessel ‘Polarstern’. The first survey in 2006/07 started south of South Africa, went to Neumayer Station in Atka Bay (70°29.6’ S/07°57.6’ W), crossed the Weddell Sea from Neumayer to south of Elephant Island and worked around the South Shetland Islands and east of the Antarctic Peninsula in front of former Larsen A and B glaciers. The second survey covered two transects: the first more westerly one started at 57°09.3’ S/00°39.1’ E and went to Atka Bay (70°29.6’ S/07°57.6’ W) whereas the second (return leg) followed a more easterly course from Atka Bay over Maud Rise to 57°03.1’ S/12° 27.5’ W. No observations could be conducted from 63 to 57°S on the return cruise due to fog (visibility < 200 m) and swell. Standard line transect survey protocols were followed while the helicopter and the ship followed track lines that could not be designed (i.e. fully randomized) in advance due to unpredictability of the ice conditions and the need to meet several objectives simultaneously. Helicopter track lines covered a total of 13 124 and, 13 417 km in 2006 and 2008 respectively while the ship survey covered 1 171 and 2 011 km respectively. We were particularly interested in the distribution and abundance of Antarctic minke whales in the pack-ice. Minke whales were primarily seen in the ice. Killer and southern bottlenose whales were also seen in the ice while all baleen whales other than minke whales, and sperm whales were only observed in open water. Humpback whales were the most frequently sighted species on the shipboard survey in 2006/07 and the helicopter survey in 2008/09. Environmental information, including proportion ice coverage, was collected continuously. One striking finding from this summary was a much higher encounter rate for all cetaceans from the ship than from the helicopter. This difference could be explained by observers on the helicopter missing more animals on the track line than those from the ship (i.e. g (0) < 1); it could equally be explained if whales, were drawn to leads created while RV ‘Polarstern’ broke the ice. This discrepancy warrants closer attention

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Keywords

• aerial survey
• Antarctica
• AWI
• dolphins
• marine mammal
• RV Polarstern
• Weddell Sea
• whales