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Polar Ecosystems Program

Bering Okhotsk Seal Surveys (BOSS): Joint U.S.-Russian Aerial Surveys

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Apr-May-June 2012
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Figure 4. Map showing on-effort U.S. survey tracks and Russian flight tracks during the 2012 ice-seal Bering Sea survey. Click map to enlarge.

Researchers from the National Marine Mammal Laboratory’s (NMML) Polar Ecosystems Program (PEP), in collaboration with Russian colleagues, conducted synoptic abundance and distribution surveys for the four species of ice-associated seals (bearded, spotted, ribbon, and ringed seals) which are known to occupy and breed in the Bering Sea during the spring and summer (Fig. 4). This effort, supported by NOAA, the Bureau of Ocean Energy Management (BOEM), and several Russian institutions, constitutes the largest survey effort undertaken to estimate the abundance of these important seal species. The fieldwork was conducted using digital cameras and thermal imagers mounted in the belly ports of two U.S. and one Russian fixed-wing aircraft from 1 April to 23 May 2012.

The U.S. surveys consisted of flights originating from airports in Nome, Bethel, and Dillingham, Alaska. The U.S. team utilized airstrips in Gambell, on St. Lawrence Island, and St. Paul, in the Pribilof Islands, to reach the most remote areas of sea ice in the central Bering Sea. The Russian team began western Bering Sea surveys in mid-April from Ossora, Russia, on the Kamchatka Peninsula and worked their way north to the Bering Strait.

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Figure 5. Paired Canon Mark III 1Ds digital SLR cameras and FLIR SC645 thermal imagers mounted in the belly port of a NOAA Twin Otter (N56RF) aircraft.

Most U.S. flights lasted 4-9 hours and were flown at an altitude of 1,000 ft (300 m) to maximize the area surveyed and minimize the chance of disturbance to seals and other wildlife. A NOAA Twin Otter (N56RF) housed three FLIR SC645 thermal imagers, which recorded continuous data in the 7.5-13.0 µm wavelength. Each thermal imager was paired with a Canon Mark III 1Ds digital single-lens reflex (SLR) camera with a 100-mm Zeiss lens. All six instruments were mounted in an open-air belly port (Fig. 5). The combined thermal swath width was approximately 1,500 ft (470 m) at an altitude of 1,000 ft. A contracted Aero Commander aircraft carried two sets of paired thermal imagers (SC645) and digital SLR cameras (Nikon D3X) and surveyed a maximum swath width of approximately 900 ft (280 m). The two aircraft flew a total of 39 surveys, which covered over 14,000 nautical miles (27,000 km) of trackline and collected more than 885,600 images.

Advanced thermal-imaging technology was used on both the U.S. and Russian survey aircraft to detect the warm bodies of seals against the background of the cold sea ice. High-resolution digital images will be used to identify the species of seals detected by the thermal imagers (Fig. 6). Novel statistical approaches will also be used to tackle the unique challenges presented by the moving and melting sea-ice habitat. A second survey in spring 2013 will complete the coverage and increase the precision of the population numbers. Ultimately, this project will provide the first comprehensive estimates of abundance for the four species of ice-associated seals found in the Okhotsk and Bering Seas.

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Figure 6. Paired thermal and visual images, of a bearded seal on Bering Sea pack ice, collected during the 2012 survey. The images were collected using a Canon Mark III 1Ds digital SLR camera with a 100-mm Zeiss lens and an FLIR SC645 thermal imager mounted in the belly port of a fixed-wing aircraft flying at an altitude of 1,000 feet.

By Erin Moreland, Michael Cameron, and Peter Boveng


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