A Preliminary Analysis of Baleen Whale Distribution Around the Western Antarctic Peninsula
in the Austral Fall and Winter

A.S. Friedlaender1, D. Thiele2, E. Hofmann3, M. MacDonald4, S. Moore5, and R. Pirzl2

1Duke University Nicholas School of the Environment, Durham, North Carolina, 27713 USA

2Marine and Migratory Wildlife Ecology Group, School of Ecology and Environment, Deakin University,
GPO Box 423, Warrnambool, Victoria, Australia 3280

3Center for Coastal Physical Oceanography, Crittenton Hall, Old Dominion University,
Norfolk, VA 23529, USA

42535 Sky View Lane, Laramie, Wyoming 82072, USA

5NOAA/National Marine Fisheries Service, National Marine Mammal Laboratory, 7600 Sand Point Way NE,
Seattle, Washington 98115, USA

The International Whaling Commission (IWC) and Southern Ocean Global Ocean Ecosystem Dynamics (SO GLOBEC) program are collaborating on an ecosystem approach to understand baleen whale distributions in Antarctica. A primary research goal is to determine the winter distribution and foraging ecology of baleen whales relative to environmental characteristics and the distribution of primary prey, Antarctic krill, Euphausia superba. Observations from the first year of U.S. SO GLOBEC survey cruises, along the western Antarctic Peninsula near Marguerite Bay (68°S, 69°W) during April-May and July-August 2001, provide a comprehensive data set that can be used to address physical and biological relationships contributing to baleen whale distribution patterns. Visual cetacean sighting observations were made using standard line transect survey protocols, and data were recorded using the Wincruz Antarctic computer-based tracking program. Sightings data show humpback (Megaptera novaeangliae) and minke (balaenoptera acutorostrata) whales present in the study region in the austral fall and winter. Sighting numbers for both species were nearly equal around Marguerite Bay in late Austral fall. A GIS, using cetacean sightings data and concurrent hydrographic measurements, show whale distributions associated with: 1) the southern boundary of the Antarctic Circumpolar Current, 2) the frontal boundary between intrusions of warm Upper Circumpolar Deep Water and continental shelf water, and 3) the frontal boundary between inner shelf coastal current and continental shelf waters. Cetacean sightings were particularly numerous along the frontal boundary formed as the coastal current exits the southern end of Marguerite Bay. Humpback whales were associated with all three frontal boundaries while minke whales were found only along the continental shelf and coastal frontal boundaries. The correspondence between the cetacean sightings and hydrographic features suggests that the austral winter distribution of cetaceans along the west Antarctic Peninsula is not random, but rather is determined in part by the structure of the physical environment, which in turn determines prey distribution. Continued analyses and collection of cetacean sightings data in conjunction with concurrent prey and hydrographic distributions will allow determination of the causal relationships underlying austral winter cetacean distributions in the Antarctic Peninsula region.