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Dispatches from the field

Studying at-risk harbor seals in western Aleutians


harbor seals
Harbor seals rest on shore of Clam Lagoon on Adak Island, Alaska  Photo: Dave Withrow, NOAA Fisheries

Harbor Seals
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September 13, 2016óRight now, Alaska Fisheries Science Center researchers are in the western reaches of US waters leading a 20-day research mission that will increase our understanding of harbor seals in the Aleutian Islands.

Harbor seals along the Aleutian chain are at risk. The population declined about 67 percent during the 1980s and 1990s, including an alarming 86 percent decline in the western Aleutians. Their numbers appear to have stabilized now but at a historically low level. Unfortunately, scientists donít know what caused the steep declines, which complicates our ability to conserve the species.

tagged harbor seal
Harbor seal swims with a back-mounted satellite tag  Photo: John Jansen, NOAA Fisheries

To better protect harbor seals, we need to know more about their health and ecology, that is, harbor sealsí relationship with their environment. Center scientists have launched new research initiatives over the past two years in hopes of unraveling the mystery of harbor sealsí past decline and current status.

Researchers have already captured and released 46 seals from the eastern and central Aleutian Islands, collecting valuable information about the animalsí diet, condition and genetic composition. They also attached two types of satellite tags on the animals which allow researchers to remotely monitor the sealsí movements, dive patterns and timing of when they are at sea versus on shore. These behavioral data are used to analyze the seals' seasonal habitat use and improve abundance estimates from aerial surveys.

taking blood
NOAA biologist Heather Ziel collects a blood sample from a captured harbor seal  Photo: Josh London, NOAA Fisheries

Now Center scientists and a collaborative team from Alaska SeaLife Center and SeaWorld are on a research vessel in the western Aleutians. They will work from Adak to Attu, until the end of September. The goal is to sample and satellite tag more harbor seals to gain critical information that will help us conserve the species now and into the future.


Meet the Team

Shawn Dahle
Shawn Dahle

Josh London
Josh London

Peter Boveng
Peter Boveng

Heather Ziel
Heather Ziel


Shawn Dahle is a biologist at the Alaska Fisheries Science Centerís Marine Mammal Laboratory. Shawn joined the Lab's Polar Ecosystems Program in 2002 after completing his M.S. in Fisheries Conservation at the University of Minnesota. His research focuses on population monitoring and status assessments of seals in Alaska.


Josh London is a wildlife biologist at the Alaska Fisheries Science Centerís Marine Mammal Laboratory. He focuses on population assessment and ecology of harbor seals and ice seals. Josh received a B.S. and Ph.D. from the University of Washington.


Peter Boveng is the leader of the Polar Ecosystems Program for research on harbor seals and ice-associated (ringed, bearded, spotted, and ribbon) seals in Alaska. His primary research interests are in the estimation of fundamental quantities for population assessment, such as abundance, trends, and vital rates, and in satellite telemetry studies of movements, distribution, and foraging behavior. Peter received Ph.D. and M.S. degrees in biology from Montana State University and a B.A. from Cornell University.


Heather Ziel is a research biologist at the Alaska Fisheries Science Center's Marine Mammal Labratory. She works in the Lab's Polar Ecosystems Program.



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