Alaska Ecosystems Research Program
Northern Fur Seal Research
Much of the northern fur seal research conducted by the Alaska Ecosystem Program continues the
National Marine Mammal Laboratory’s (NMML) long-term population monitoring study on the
Pribilof Islands. The annual count of both territorial adult males with females and idle adult males
was made in July 2004. The number of territorial males was estimated to be 3,286 on St. Paul Island
and 760 on St. George Island. The number of idle males was estimated to be 5,027 on St. Paul Island
and 905 on St. George Island. The percentage of idle males declined on both islands from last year
(idle = 33.6% on St. Paul Island and 21.8% on St. George Island), and territorial males declined by
10% on St. Paul and increased by 6.1% on St. George. Pup numbers are estimated biannually
and were counted in August 2004. We estimated 122,803 pups (SE = 1,290) were born on St. Paul
Island and 16,876 pups (SE = 239) were born on St. George Island. Pup production continued to decline
on both islands from previous years. The 2004 estimate for St. Paul Island is 15.7% less than the
estimate in 2002 and 22.7% less than the estimate in 2000. The 2004 pup production estimate for
St. George Island is 4.1% less than the estimate in 2002 and 16.4% less than the estimate in 2000.
To continue the work published in Robson et al. (2004), which demonstrated habitat partitioning by
island and rookery complex, we instrumented 39 parturient female northern fur seals with satellite
tags in August 2004. Nineteen adult female northern fur seals were captured on St. Paul Island, and
20 were captured on St. George Island. All fur seals were outfitted with satellite tags to collect
location data to track the animals’ movements, with 28 animals having additional instruments to
collect data on diving patterns (12 on St. Paul Island and 16 on St. George Island). The satellite
tags were left on the animals for multiple foraging trips in order to examine habitat site fidelity
among individuals. In late September and early October, 33 of the instrumented animals were
recaptured to recover the tags.
By Tonya Zeppelin
California Current Ecosystems Program
San Miguel Island Research
Resighting effort to determine survival and reproductive rates of branded California sea lions
and flipper-tagged adult northern fur seals began in May and continued through August. Live-pup
counts were conducted during July and August to assess the total pup production for both species.
Dead pups were counted for each species starting in July and will continue through October to document
the level and causes of pup mortality. Hookworms appear to be a major factor in mortality of both sea
lion and fur seal pups.
During July, an effort was made to recapture the four 3-year old California sea lions that were
outfitted with satellite telemetry instruments and from which blubber tissue biopsies were obtained
during April. These animals were sampled and instrumented as part of two studies: 1) to describe the
spatial patterns and distribution of juvenile sea lions using San Miguel Island; and 2) to assess the
bioaccumulation rates of environmental pollutants by California sea lions. Preliminary exploration of
the satellite telemetry data indicate that the animals frequented San Miguel Island and made daily or
multiple-day trips to forage in the southern California Bight and north of San Miguel. To date, these
individuals have not been recaptured.
In September the old field station on San Miguel Island was demolished and removed from the island.
Work on the new station is essentially complete.
Harbor Seal Research
Observations of tagged and branded harbor seals at Gertrude Island, south Puget Sound, Washington,
began in early July and will continue until the end of October. The peak number of seals was 526 in
mid-August. About 110 pups were observed. These counts are similar to previous years. Resights of
tagged and branded seals are used to determine survival, natality, and age of first reproduction.
During the month of September, 64 harbor seals were caught and tagged; 52 of those were branded,
increasing the number of seals branded since 1993 to 573.
Steller Sea Lion Research
Since July 2001, Steller sea lion pups have been tagged and branded at rookeries in southern Oregon
and northern California to determine survival, movements, and distribution of yearlings and juveniles.
Another cohort of 180 pups was branded at St. George Reef, California, in July 2004. Bimonthly vessel
and land-based surveys to resight branded sea lions were conducted in northern California, Oregon and
Washington. In addition, a series of remote cameras was installed at Rogue Reef, Oregon, for the third
year to assist in brand resights and a resight network established with biologists from Pacific Rim
National Parks, British Columbia, Canada. Preliminary evidence collected since 2001 indicates a general
northward movement/dispersal of pups and juvenile Stellers into Washington and British Columbia
beginning in September.
Sea Lion Symposium
Five members of the California Current Ecosystems Program presented oral (3) or poster (2)
presentations at the Sea Lions of the World Symposium held during 30 September through 3 October
in Anchorage, Alaska. The symposium was held to bring the international community of sea lion
researchers together to address issues concerning the five species of sea lions.
By Harriet Huber
AFSC Quarterly Research Reports July-Sept 2004