Seasonal variability in whale encounters in the Western Antarctic Peninsula
Deborah Thiele1, Edwin Chester1, Sue Moore2, Ana Širovic3, John Hildebrand3 and Ari Friedlaender4
1Whale Ecology Group - Southern Ocean,
2NOAA/AFSC/National Marine Mammal Laboratory;
Multidisciplinary cruises were conducted in the SO GLOBEC, Western Antarctic Peninsula (WAP) study region under US and German programs during 2001 and 2002, focusing on winter processes that affect krill and their predators. The International Whaling Commission (IWC) conducted whale sighting surveys on all cruises. These data provide a series of seasonal (late summer, autumn and winter) snapshots of one region over two years with very different ice conditions. The visual data are complimented by concurrent passive acoustic studies that extend the spatial and temporal sampling beyond the study region and cruise dates. A circum-Antarctic long term program of baleen whale research has now been implemented: its design was facilitated by experience in integrating visual sighting with acoustic and other technologies, gained on the 2001 and 2002 cruises. The very different ice conditions in 2001 and 2002 provide a basis to explore the effects of variability in physical and biological processes on whale distribution and relative abundance. Although whale distributions varied somewhat between the two years, there was nevertheless a strong concordance of distribution in relation to biological processes that were linked to physical features in both years. Here we suggest that regional variability such as that observed in the WAP area can be analyzed in the context of global anomalies affecting Antarctic climate, using existing historical records of whale distributions and catch records.