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Alaska Ecosystems Program

Northern Fur Seal Research in 2010

see caption
Figure 1. Sheared and unsheared pups on East Reef rookery, St. George Island, Alaska, 2010. Photo by Jamie King.

The National Marine Mammal Laboratory’s (NMML) Alaska Ecosystems Program (AEP) conducted a number of studies on northern fur seals (Callorhinus ursinus) during 2010 with field components that began in July and continued through October. The primary research objectives of monitoring population trends and investigating the ecology and health of the fur seal population on the Pribilof Islands (St. Paul and St. George) were accomplished through a variety of projects, including studies of pup condition, causes of mortality, and testing of telemetry devices. However, the majority of the AEP’s research efforts involved three projects that collected data on fur seal abundance, fine-scale foraging behavior of adult females in the Bering Sea, and age-specific vital rates of females on St. Paul Island.

Northern fur seal abundance and population trends were assessed on the Pribilof Islands during 2010 by btaining counts of adult males and estimates of the numbers of pups born. Adult males were counted in July, and pups were sheared (Fig. 1) in August 2010. Analyses of the summer’s population assessment data will occur at the conclusion of this year’s field seasons.

Fine-scale foraging behavior studies of northern fur seals were conducted during August–October 2010 at St. Paul and St. George Islands. Specific objectives of the project were to obtain higher-resolution location and diving data during adult female foraging trips in the Bering Sea. Twenty-two instruments were deployed on St. Paul Island on females at four different rookeries, and 10 were deployed on St. George Island on females at two different rookeries. Known-age females were targeted at Polovina Cliffs rookery on St. Paul Island and on South Rookery on St. George Island.

Research efforts by the AEP on age-specific vital rates of northern fur seals continued on St. Paul and St. George Islands in 2010. Fieldwork on St. George Island focused on demographic objectives: tagging females for mark-recapture studies, extracting teeth for age estimation, large-scale pup tagging, and initiation of tag sighting and behavioral observations. Fieldwork on St. Paul Island focused on tag-sighting efforts throughout the summer and large-scale pup tagging in the fall.

By Rod Towell


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