Diving Behaviors and Movements of Juvenile Steller Sea Lions (Eumetopias jubatus) Captured in the Central Aleutian Islands, April 2005

摘要

From the late 1970s to the early 1990s, the endangered western distinct population segment (wDPS) of Steller sea lions (Eumetopias jubatus) in the United States declined to less than 75,000 animals, equating to a reduction of approximately 80% (Loughlin 1998, Calkins et al. 1999). Initially, a precipitous decline was observed during the 1970s in the eastern Aleutian Islands (Braham et al. 1980) and then it spread east to the central Gulf of Alaska and west to the central Aleutian Islands (CAI) during the late 1980s (Merrick et al. 1987). The rate of decline decreased during the 1990s (NRC 2003) and from a regional perspective, rates of decline were greater at the fringes of the wDPS' geographical range than at the center. Population trends, which are dependent on the temporal scale examined, have varied among sub-regions of the U.S. wDPS, including the eastern, central, and western Gulf of Alaska, and eastern, central, and western Aleutian Islands (including the eastern Bering Sea). Overall, the population of Steller sea lions has stabilized in many areas since 2002, but recent trends in the western Aleutian Islands (WAI) and western CAI have been negative, suggesting a stable or slight negative trend for the population as a whole.