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Alaska Ecosystems Program

Remote Cameras Increase Sightings of Marked Steller Sea Lions

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Tracking the demography of Steller sea lions in Alaska is a fundamental requirement to understanding population viability. Permanently marking Steller sea lion pups with an individual identification mark and then observing them throughout their life provides information to estimate survival and reproductive rates of the population, as well as understand their distribution and movements.


Figure 1. Biologists with the National Marine Mammal Laboratory work on remote cameras at Gillon Point (Agattu Island), Alaska. Photo NOAA Fisheries.


Since 2000, scientists with the Center’s National Marine Mammal Laboratory (NMML) have branded Steller sea lion pups in the western stock in Alaska at Ugamak, Marmot, Sugarloaf, Seal Rocks, and Fish islands during June and July. Observation effort by ship or land-based personnel is used to determine age/sex/cohort/rookery-specific survival, as well as age at first reproduction and reproductive rates.

In 2011, this study was expanded to the western portion of the Aleutian Islands in response to the continued significant decline of Steller sea lions. The application of permanent marks to pups in the farthest reaches of the Aleutian Islands began in 2011 at Gillon Point (Agattu Island) with additional cohorts marked in 2013 and 2015. A second rookery at Hasgox Point, Ulak Island, was added in 2013 and was also included in 2015.

Since the Aleutian Islands are too remote to establish field camps, the National Marine Fisheries Service (NMFS) has staged remote digital cameras at six different sights on five islands (Fig. 1). The 20 remote cameras (Fig. 2) capture images (Fig. 3) every 5 to 20 minutes during daylight hours throughout the entire year. These images are retrieved once or twice a year and analyzed at NMML facilities by volunteers and NMFS biologists to look for branded sea lions. Along with marked animals from the western portion of the Aleutian Islands, a few sea lions that were marked in Russia as pups have been seen.

  Figure 2. The six Steller sea lion sites in the western portion of the Aleutian Islands where 20 remote cameras capture images of marked sea lions. Sea lion pups have been marked on Gillon Point (Agattu Island) and Hasgox Point (Ulak Island) rookeries. (Number of cameras dedicated to each site shown in parentheses)

Figure 3. An image from a remote camera stationed at Hasgox Point (Ulak Island) rookery captured during the peak summer breeding season. Photo NOAA Fisheries.


By Kathryn Sweeney


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