Cetacean surveys in the Southern Ocean using icebreaker-supported helicopters

Cetaceans in the Southern Ocean are potentially impacted by anthropogenic activities, such as direct hunting or through indirect effects of a reduced sea ice due to climate change. Knowledge on the distribution of cetacean species in this area is important for conservation, but the remoteness of the study area and the presence of sea ice make it difficult to conduct shipboard surveys to obtain this information. In this study, aerial surveys were conducted from ship-based helicopters. In the 2006/07 (ANT XXIII/8) and 2008/09 (ANT XXV/2) polar summers, the icebreaker RV 'Polarstern' conducted research cruises in the Weddell Sea, which offered the opportunity to use the helicopters to conduct dedicated cetacean surveys. Combining the results from both cruises, over 26,000 km were covered on survey effort, 13 different cetacean species were identified, and a total of 221 cetacean sightings consisting of a total of 650 animals were made. Using digital photography, it was possible to identify four different beaked whale species and to conduct individual photo-identification of humpback and southern right whales. Helicopter surveys allow the collection of additional information on sightings, (e. g. group size, species), as well as the coverage of areas with high ice coverage. The flexibility and manoeuvrability of helicopters make them a powerful scientific tool to investigate cetaceans in the Southern Ocean, especially in combination with an icebreaker.