Cetacean habitats in the Alaskan Arctic

This dissertation is based upon cetacean sighting data from ten years (1982-91) of aerial surveys offshore northern Alaska. The first chapter provides an introduction to the physical oceanography of the Alaskan Arctic, and to seasonal patterns of distribution, migration, and feeding ecology for bowhead whales (Balaena mysticetus), white whales (Delphinapterus leucas) and gray whales (Eschrichtius robustus). The effects of aircraft configuration, species, group size, behavior and environmental features on the detection distance of surfaced whales is examined in Chapter 2. Detection distance varied primarily with animal size, group size, behavior and ice cover. Germane to interpretation of habitat selection in subsequent chapters is the result that ice cover hampered the detection distance of bowhead whales, but not white whales.; Cetacean distribution and habitat selection are topics of the last two chapters. Seasonal differences in habitats based upon classification by bathymetry and ice cover are presented in Chapter 3. Between summer and autumn, bowhead whales shifted from continental slope to inner shelf, and white whales from slope-basin to slope habitat in the Alaskan Beaufort Sea. Gray whales were strongly associated with the Chirikov Basin in the northern Bering Sea in summer, and with shallow shoal and coastal habitat in the northern Chukchi Sea in both summer and autumn. Selection of ice-cover habitat was less straightforward. For example, in autumn, bowheads selected {dollar}{dollar}70% ice habitat in the northern Chukchi Sea.; The effects of oceanographic climate on cetacean habitat selection is examined in Chapter 4. Bowhead whales exhibited greater habitat selection variability than either white or gray whales. In the Alaskan Beaufort Sea, bowheads selected outer shelf and slope habitat in heavy-ice conditions, while white whales remained associated with slope waters in all ice cover conditions. In the northern Chukchi Sea, gray whales occupied shallow coastal/shoal waters in all conditions, but selection of this habitat was especially strong in high-transport years. In years of moderate and low-transport, bowhead and gray whales selected shelf/trough habitat, possibly in response to migratory cues evident in the currents channeled there.