Spotting an animal that blends into the ice, from an aircraft at 150 knots and 1,000 feet, is hard. So in 2016 American and Russian government scientists flew the Chukchi Sea with infrared cameras, which pick out warm bodies, paired with high-resolution cameras to identify what they found: seals and polar bears on the sea ice.
Why
The survey, by NOAA Fisheries and the Russian State Research and Design Institute for the Fishing Fleet, aimed at the first comprehensive, reliable abundance estimates of ringed seals, bearded seals and polar bears there. Bearded and ringed seals are vital to northern coastal Alaska Native communities and key species in Arctic ecosystems, yet across much of their range nobody knows how many there are. Estimates and maps underpin decisions on co-management, conservation and permits for activities that could affect them.
Ice seals
Bearded, ringed, ribbon and spotted seals are known together as ice-associated seals: they rest and raise their young on sea ice at key times of year. Because they also spend much time in the water, counting them is difficult. Only ringed and bearded seals are in the Chukchi Sea at that season, so the survey focused on them.
Ringed seal. NOAA Fisheries.
Bearded seal. NOAA Fisheries.
Spotted seal. NOAA Fisheries.
Ribbon seal. NOAA Fisheries.
The best time to count is the breeding and molting season, when seals haul out on the ice, the NOAA lead scientist explained, and repeated counts show long-term trends and how the species respond to a changing climate. Surveys ran from April to mid-June: early flights found mostly bearded seals and polar bears, and more ringed seals were expected from mid to late May, as they leave their snow lairs to bask. In 2016 that was harder than usual: a warm winter broke up the pack ice early.
Flying higher
Earlier surveys relied on observers looking out of the windows, at about 400 feet. Cameras let this one fly at about 1,000 feet, which greatly reduces disturbance to the seals, to other animals, and to subsistence hunters. Most of the work stayed far from shore and villages, and the team avoided flying over or near hunting areas for bowhead whales, walrus, bearded seals and other marine mammals.
Similar joint surveys of the Bering Sea in 2012 and 2013 gathered more than 2.2 million photographs and 5.4 TB of thermal video, improving estimates for all four ice seal species there.
Polar bears were counted too, with U.S. Fish and Wildlife Service scientists aboard: a predator of seals, and important to Alaska Native communities for food and tradition.
What the cameras see
In flight, observers watch the camera feeds on screens, along with a map of the planned tracks and a display from each of three thermal cameras.
The cameras’ feeds and track map on screen. NOAA Fisheries.
A thermal image shows warm hot spots; the high-resolution photo taken at the same moment shows what they are.
Two hot spots in a thermal image… NOAA Fisheries.
…and the photograph taken at the same moment: two bearded seals. NOAA Fisheries.
Some had thought polar bears were invisible to infrared. The survey showed otherwise: a bear shows clearly as a hot spot.
Thermal image (left) and photograph (right): the circled polar bear matches the hot spot. NOAA Fisheries.
Close up: a polar bear. NOAA Fisheries.
Sources
- NOAA Fisheries, "Bilateral Effort Underway To Assess Populations Of Arctic Seals And Polar Bears"; rewritten in hubnx's own words. Illustrations, photographs and thermal images: NOAA Fisheries.
Licence: CC0 1.0 (public domain) · Adapted from www.fisheries.noaa.gov
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