NATIONAL MARINE MAMMAL LABORATORY (NMML)

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
The purpose of the Steller sea lion research was to capture juvenile (<3 years old) Steller sea lions, determine their condition through tissue sampling and morphometric measures, and deploy up to 10 satellite-linked depth recorders to track the animals’ movements and diving patterns off the east side of Kodiak Island.  The work was performed in conjunction with studies of oceanography and fish abundance and distribution in the areas of Marmot Island, Long Island,  and Cape Chiniak by researchers with the University of Alaska Fairbanks (UAF), and with studies of trawl fishery effects on fish distribution and abundance in Chiniak and Barnabus Troughs by the Center’s Resource Assessment and Conservation Engineering (RACE) Division.

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
Northern fur seal research conducted by the AEP is a continuation of the NMML’s long-term population monitoring study. Numbers of northern fur seal pups were estimated by shear-sampling, a mark-recapture method, on the Pribilof Islands in August 2002. AEP staff estimate 145,701 (SE  = 1,629) pups were born on St. Paul Island and 8,262 (SE = 191) born on Sea Lion Rock, a small island approximately 500 m from St. Paul Island.  They also estimate 17,060 (SE = 526.6) pups were born on St. George Island.  During 1998-2002, pup production declined on St. Paul Island at 5.14% per year (SE = 0.26%,  P =0.03) and at 5.35% per year (SE = 0.67%, P = 0.08) on St. George Island. For the Pribilof Islands as a whole (excluding Sea Lion Rock), pup production declined at  5.20% per year (SE = 0.19%, P = 0.02).  Estimated pup production is now below the 1921 level on St. Paul Island and below the 1916 level on St. George Island; during those years, the northern fur seal population was increasing at about 8% per year as it recovered from a pelagic harvest that took place in the late 19th and early 20th centuries. On Sea Lion Rock, pup production is slightly greater than the 8,061 pups counted in 1922.

U.S.-Russia Meeting
AEP staff attended the 2nd Russian Marine Mammal Council meeting and then the 17th Working Group Meeting of the U.S.-Russia Agreement on Cooperation in the Field of Environmental Protection which were held consecutively at Listviaynka, Lake Baikal, Russia during 6-19 September.  The AEP Leader is the U.S. chair of the Marine Mammal Working Group which meets about every 18 months to discuss collaborative research and to share information on marine mammals of mutual interest.  Results of the workshop found in a protocol signed by each nation is available on the web at  http://nmml.afsc.noaa.gov/AlaskaEcosystems/sslhome/
protocolUSRus.htm.

By Tom Loughlin.

California Current Ecosystems

San Miguel Island
Population assessment studies of California sea lions and northern fur seals were conducted from May through September at San Miguel Island, California.  The field research in 2002 was a continuation of long-term studies of survival, recruitment, natality, and health of California sea lions and northern fur seals.

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.

Harbor Seals
Observations of marked and branded harbor seals began in July and will continue until the end of October.  Resighting of branded seals gives information on age-specific natality and survival.  Analysis of data from 1993 to 2001 indicates that survival in the first year is about 60% and thereafter about 90%.  This is unusual, in that most subadult (age 1 to 3) animals have lower survival rates than adults. First age of reproduction was age 3, but only a small proportion of females gave birth then.  By age 7, all females have been recruited into the population.

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
In early July, seven time-depth recorders were attached with suction cups to southern resident killer whales in the San Juan Islands region.  From these instruments we got 78 hours of data – increasing our database by 25%.  Of note were dives in excess of 100 m including some dives to over 200 m.  Some of the deep dives occurred at night. We were also successful in deploying a “critter cam” (video camera) on one of the killer whales.  No foraging was observed during the hour and a half of video obtained.  While the camera was in place, the whales appeared to be socializing.

Harbor Porpoise Aerial Surveys
Cascadia Research Collective, under contract to the NMML, conducted aerial surveys of harbor porpoise from 5 August to 16 September.  The survey covered U.S. and Canadian waters from 42EN to 50EN from the coast to the 200 m isobath and the inland waters of Washington State and British Columbia to 50EN.  The inland portions of the survey were timed to occur at the same time as NMML’s small boat surveys.  The concurrent surveys this year and in the next 2 years will be used to develop a calibration between aerial and small boat surveys in the inland waters.

Inland Washington Waters Small Cetacean Boat Survey
From 12 to 30 August, boat surveys were conducted for small cetaceans in the eastern Strait of Juan de Fuca and San Juan Island area to coincide with harbor porpoise aerial surveys described above.  Weather conditions during the surveys were excellent: the majority of the 1,151 km of effort were conducted in conditions less than Beaufort sea state 1.  As a result, a large number of sightings were obtained, including 817 harbor porpoise and 54 Dall’s porpoise.

Washington Harbor Porpoise Movements
From 16 September to 2 October eight harbor porpoise were tagged with satellite and VHF transmitters off the mouth of the Sekiu River to provide movement data relative to stock boundaries.  As of early October, some of the porpoises moved northwest of Neah Bay while others moved east into the central Strait of Juan de Fuca.

By Harriet Huber.

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AFSC Quarterly
Research Reports
July-Sept 2002