Alaska Ecosystems Program
Alaska Ecosystem Program (AEP) staff conducted field research on Steller sea lions (Eumetopias jubatus) in July near Kodiak Island, conducted northern fur seal (Callorhinus ursinus) research in August on the Pribilof Islands, and chaired a U.S.-Russia meeting on marine mammals at Listviaynka, Lake Baikal, Russia, during September.
Steller Sea Lion Research
A total of 17 juvenile sea lions were captured at Marmot Island (5), Chiniak Island reefs (2), and Two-headed Island (10) during 24 July-3 August 2002. Captured sea lions weighed 77.4-162.2 kg and comprised 8 females and 9 males. Ten sea lions were outfitted with SDR/VHF (satellite depth recorder/very high frequency) transmitters (Marmot Island n=3, Chiniak Island n=2, Two-headed Island n=5); and two of them had completed molting in the attachment area, so the SDRs were attached to new fur. Two sea lions had been captured and instrumented previously during the March 2002 capture trip. Both (one male and one female) grew 18 cm in length, but the male gained about 41% in body mass and 16 cm in girth, while the female gained about 28% and had no increase in girth.
Blood and blubber samples were obtained from all captured sea lions, genetic samples from 15 (since the two prior captures had already been sampled), and fecal samples from 8. The two recaptured sea lions still possessed both fore-flipper tags, and previous blubber and flipper biopsy sites were fully healed.
Twenty sea lions branded or tagged on previous trips were observed, including a female branded as a pup in 1988 at Marmot Island. Most observations were of sea lions branded as pups at Marmot Island, but also included a 1-year old observed at Chiniak Island that had been branded at Fish Island, and five that had been dive-captured during previous cruises.
The AEP has implemented a new service on its web site where the public can monitor the movements of sea lions at sea with satellite attached transmitters. The movement of the animals can be viewed at: http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/Satellite/Default.htm
Northern Fur Seal Research
By Tom Loughlin.
California Current Ecosystems
San Miguel Island
In 2002, total production for California sea lions was 23,604, which represents a 1.5% increase from 2001. The observed pup mortality rate was 21.8% by 3 months of age. We began a study investigating the causes of California sea lion pup mortality in the first year of life in June 2002. We collected up to 30 fresh dead California sea lion pups once each month between June and September and conducted a complete necropsy on each pup. Hookworm infection rates were near 100% . It is likely that these infections are a significant cause of mortality of California sea lion pups and may have a population level effect on the dynamics of the population if the high incidence and mortality continue over several more years. We plan to continue to monitor the health of the population to document the population response to this density-dependent parasite.
In September, 500 sea lion pups were branded marking the 15th year of branding at San Miguel Island. The branding study continues to provide data for estimation of age-specific survival and natality and recruitment rates of sea lions and will provide insight into the impacts of environmental changes and disease on the vital parameters of the population. In 2002, a total of 7,092 observations of 1,695 individually branded California sea lions, ages 1 to 15, were recorded between June and August 2002. The number of females with pups decreased 14% from 2001. The decrease in the number of pupping females may reflect adult female mortality related to a large-scale demoic acid event in the spring of 2002. More than 400 adult and juvenile sea lions were stranded along the central California coast. Most of those animals that were transferred to rehabilitation centers died due to demoic acid toxicity in the brain.
In 2002, total production of northern fur seals on San Miguel Island was 1,947, a 4.3% decrease from 2001. The northern fur seal pup production has slowly increased since the 80% decrease in pup production in 1998, but in 2002 production was still 37% below 1997 production. The slow recovery of the population from the 1997-98 El Niño event indicates that adult mortality occurred then, in addition to pup and juvenile mortality, and that full recovery of the population may be several years in the future.
Resights of tagged fur seals are also providing information on age-specific survival and recruitment of the small population at San Miguel Island. In September, 300 northern fur seal pups were tagged to continue long-term studies for estimation of vital parameters of this population.
Manuscripts on the age-specific survival and natality rates and the causes of pup mortality of California sea lions are being prepared for publication.
Aerial surveys of the five regions in the inland stock (San Juan Islands, Eastern Bays, Strait of Juan de Fuca, Puget Sound, and Hood Canal) were flown in August and September. Numbers appear consistent with previous years in all areas except Hood Canal, where numbers of seals appeared to be lower than in recent years. This may be a function of some seals in Hood Canal changing their preferred haul-out time from high tide to low tide.
During 18-20 September, 48 harbor seals were captured. In addition to tagging and branding efforts, blood samples were taken for disease screening, blubber samples were taken for contaminant analysis, and tissue samples were taken for genetic analysis of the inland waters stock structure. Four subadults tested positive for Brucella, which is consistent with past results.
Southern Resident Killer Whale Foraging Behavior
Harbor Porpoise Aerial
Inland Washington Waters Small Cetacean Boat Survey
By Harriet Huber.
Auke Bay Lab