Issue
The western population of Steller Sea Lions (SSL) has been in decline
for several decades and is now considered endangered. There are several
possible factors causing this decline, including an increase in parasites
and disease, predation by killer whales, nutritional stress caused
by competition with other species for food and/or changes in abundance,
quality and distribution of prey, and environmental factors such as
pollution and climate change. Current management efforts are focused
only on commercial fishing in habitat critical to the SSL, which is
thought to cause a harmful reduction in SSL prey availability.
Approach
To determine if other factors might be important in the decline of
the western SSL population, NCCOS' Center for Sponsored Coastal Ocean
Research (CSCOR) has been directed to conduct research focused on potential
changes in predator/prey relationships in the Gulf of Alaska and the
Bering Sea. This research is coordinated with NOAA
Oceanic and Atmospheric Research, which is supporting studies on
the potential impacts of ocean climate regime shifts on Steller Sea
Lion populations. The studies are implemented through the Cooperative
Institute for Arctic Research.
Predator-Prey Investigations of Killer Whales and Steller Sea
Lions in Alaska - This project addresses the role that killer
whale predation plays in the decline of Steller sea lions. Scientists
from the North Pacific Universities Marine Mammal Research Commission
will involve the local mariner community to assess knowledge of the
abundance and distribution of killer whales, and initiate a photo-census
to keep track of whales in the region. Direct observations of killer
whale predation will estimate the impacts of predation on recovery
of SSL populations. Data derived from this study will be incorporated
into a model of killer whale predation, which is funded through the
North Pacific Marine Mammal Research Commission.
The Role of Physiological Constraint in the Acquisition of Foraging
Ability: Development of Diving Capacity in Juvenile Steller Sea Lions -
This project looks at the reduction in juvenile survival as a cause
of SSL population decline. It examines the diving capacity of juvenile
SSLs, and how diving ability may change with development; as well
as how juveniles forage and what constrains their feeding ecology.
The University of Alaska will work in collaboration with the National
Marine Mammal Laboratory in the collection of animals for physiological
measurements. The results should allow determination of when and
why juveniles are most vulnerable to ecological disturbances such
as prey removal, and help identify factors that have a high probability
of impacting successful recruitment.
Seasonal Assessment of Prey Competition between Steller Sea Lions
and Walleye Pollock - The diets of walleye pollock and Steller
Sea Lions overlap, including prey such as forage fish and juvenile
pollock, yet the role of pollock as a prey competitor of SSLs has
not yet been examined. This project will determine the current importance
of juvenile pollock in the diet of SSLs and adult pollock to predict
how the pollock population affects the population of SSLs as ocean
conditions and fish communities change. Ultimately, the project could
address the efficiency and effects of restricting pollock harvests
inside SSL critical habitat areas.
Investigation of Foraging Behavior of Steller Sea Lions in the
Vicinity of Kodiak Island, Alaska - This project will locate
and quantitatively assess overwintering herring and SSL populations
in the vicinity of Kodiak Island. Their distributions in the west
will be compared to those in the east (Prince William Sound) during
the crucial fall-winter feeding period. This will provide direct
observational evidence of SSL foraging behavior, a current gap in
knowledge about SSLs. NOAAs Environmental Technology Laboratory will
work in collaboration with the Prince William Sound Science Center
and the Alaska Department of Fish and Game on this project.
Climate-driven Bottom-up Processes and Killer
Whale Abundance as Factors in Steller Sea Lion Population Trends
in the Aleutian Islands - COP and NOAA's Office of Oceanographic
and Atmospheric Research (OAR) are jointly funding this large, integrated
ecosystem study. It comprises measurements of primary production,
zooplankton distribution and abundance, and forage fish and seabird
distributions. Collaboration with the National Marine Mammal Laboratory
will allow determination of diet and foraging locations of SSLs,
and abundance estimates and identification of killer whales in the
region. These measurements will be taken in conjunction with OAR's
ongoing physical and nutrient measurements by the NOAA Pacific Marine
Environmental Laboratory. Comparisons of two regions, the Seguam-Amukta
Pass area where SSL populations are in decline and the Akutan-Unimak
Pass area where they are stable, will provide insight into the physical
and biological factors affecting SSL population decline. The study
will provide the first comprehensive investigation of the ecosystem
supporting SSLs in critical habitat areas.
For more information:
Elizabeth Turner
CSCOR/Coastal Ocean Program
phone: 301-713-3338
e-mail: coastalocean@noaa.gov
Last Updated: May 15, 2003