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Sea Lion Science Takes to the Skies - Post 1

June 14, 2021

Join Alaska Fisheries Science Center staff as they survey and photograph Steller sea lions in Alaska aboard a NOAA Twin Otter aircraft.

Aerial photo of Steller sea lions on rocks surrounded by foaming sea waves. Aerial survey image of Steller sea lions on a rocky island. Credit: NOAA Fisheries.

Week of June 6, 2021

This summer, AFSC staff are partnering with NOAA’s Aircraft Operations Center to conduct our annual aerial survey of Steller sea lions in Alaska. We canceled the 2020 survey due to the COVID-19 pandemic and, after two years away, we are so excited to get back in the field!

Monitoring the abundance (how many) and distribution (location) of Steller sea lions is one of the top priorities of the Alaska Ecosystems Program (AEP) of the Marine Mammal Laboratory . Each summer, sea lions gather on shore to give birth, mate, and care for newborn pups. We take advantage of this season to count how many sea lions are on land and, in turn, estimate changes in their population size.

Photo of a NOAA Twin Otter aircraft flying against a clear blue sky.
NOAA Twin Otter aircraft in flight. Credit: NOAA Fisheries.

Our tried-and-true method for collecting count data is an aerial survey - in fact, Steller sea lions have been surveyed this way since the 1950s! With the help of NOAA’s Aircraft Operations Center, we fly over known sea lion rookery (or breeding) and haul-out sites in a Twin Otter airplane. Cameras mounted in the belly of the plane take high-resolution images of the sites below (more on this in a future post). Back in Seattle, researchers review those images and count the number of Steller sea lions at each site.

Photo of three cameras and their mounting apparatus in a NOAA Twin Otter aircraft.
Aerial survey camera system installed in the belly of the Twin Otter. The three cameras (center of image) take simultaneous high-resolution photos of sea lion sites. They are controlled by a computer (not pictured) that also records the GPS location, altitude, and speed of the airplane. Credit: NOAA Fisheries.

There is a catch, though: the window of opportunity to photograph the most sea lions on land is only about three weeks. After that, they begin to disperse (including the young pups!) and spend more time at sea. Despite our ability to cover a lot of ground in the Twin Otter, Steller sea lion sites are spread out over more than 2,500 miles of Alaskan coastline and weather conditions aren’t always favorable enough to fly safely and capture high-quality images. For these reasons, we split sites into three survey areas (see image below). In the Twin Otter aircraft, Southeast Alaska and the Gulf of Alaska are surveyed in odd-numbered years and the eastern and central Aleutian Islands are surveyed in even-numbered years. Most summers, AEP also conducts unmanned aerial system surveys of sites in the central and western Aleutian Islands as part of a Steller sea lion research cruise.

Map of Alaska showing the UAS Aleutian Islands survey area, even-numbered years manned survey area in the Aleutian Islands, and the odd-numbered years manned survey areas in the Aleutian Islands and southeast Alaska.
Map of Steller sea lion rookery (red triangle) and haul-out (blue circle) sites in Alaska. We use the Twin Otter aircraft to survey sites in Southeast Alaska and the Gulf of Alaska in odd-numbered years, and the eastern and central Aleutian Islands in even-numbered years. We use unmanned aerial systems (UAS) to survey the central and western Aleutian Islands. Photo Credit: NOAA Fisheries.

This year’s trip will be a little different from usual because we are incorporating extra safety measures to keep our field team healthy and COVID-free. Burlyn (co-blogger) and I will share more about this next week while we complete our 7-day Shelter in Place period in Anchorage. Until then, we’ll be busy preparing for our trip and packing warm clothes, sturdy shoes, datasheets, our marine mammal research permit, some books and crafts, and safety supplies! What would YOU bring on a four-week trip to Alaska?

Side by side photos of items to be packed for trip.
Some of the items that Burlyn (left) and I (right) will be packing for the aerial survey, including safety supplies (thermometers, disinfecting wipes, face coverings), data collection materials (notebook, pencils), warm layers (hats), and fun down-time activities (books, knitting, puzzles). Credit: NOAA Fisheries.
Next: Sea Lion Science Takes to the Skies - Post 2

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