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Polar Ecosystems

Harbor Seal Research in the Aleutian Islands, 2015

Research Reports
Summer 2015
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Figure 1. Locations and numbers of harbor seals captured in the eastern and central Aleutian Islands during September 2015

A team composed of eight biologists from the National Marine Mammal Laboratory’s (NMML) Polar Ecosystems Program, a veterinarian from the Marine Mammal Center of Sausalito, California, and a traditional ecological knowledge expert from the Aleut village of Atka, Alaska, conducted a research project on harbor seals in the Aleutian Islands aboard the chartered research vessel Norseman during 5-23 September 2015. The goal of this project was to collect baseline information on harbor seal health, behaviors, and genetics in the eastern and central Aleutian Islands to increase our understanding of this population’s status, ecology, and structure.

The research team captured a total of 31 seals at six different locations between Unalaska and Atka Islands (Fig. 1). The seals comprised a fairly representative sample of sexes and age classes (Table 1). Captured seals were examined, measured, and weighed to assess their physical condition. Blood and tissue samples were collected to analyze their health, physiology, diet, and genetic composition.

Table 1. Sex and age-class composition of captured harbor seals in the eastern and central Aleutian Islands during September 2015.




Weaned Pups

















Satellite tags were glued to hair on the heads or backs of 27 seals that had sufficiently completed their annual “molt” (shedding and regrowth of hair and skin) (Fig. 2). These tags will transmit the seals’ movement, dive, and haul-out behaviors for up to 1 year and then will fall off during next year’s molt. Smaller satellite tags were also attached to 25 of the subadult and adult seals whose hind flippers were large enough to accommodate the tags (Fig. 3). These tags will remain attached throughout the molt cycle and continue to transmit location and haul-out data during this important time of year.

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Figure 2. A satellite tag attached to the head of an adult male harbor seal. Photo by Shawn Dahle, NOAA Fisheries.

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Figure 3. A satellite tag attached to the hind flipper of an adult male harbor seal. Photo by Josh London, NOAA Fisheries.

A similar project was conducted during September 2014 in Clam Lagoon, Adak Island, Alaska, where 15 harbor seals were captured, sampled, and tagged. Another research cruise covering the central and western Aleutian Islands is planned for September 2016 to expand the spatial and temporal range of our dataset.

By Shawn Dahle




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