International Survey Counts Bowhead and Beluga Whales in the Beaufort Sea

Bowhead whales. Image captured during the 2025 aerial survey over the Beaufort Sea. Photo taken while working under authority of NOAA Fisheries Research Permit #25563-02. Credit: NOAA Fisheries & CICOES / Skyla Walcott

In 2025, NOAA and the Alaska North Slope Borough successfully completed a survey to count bowheadand belugawhales in the U.S. and Canadian Beaufort Seas and Amundsen Gulf. This international, multi-agency, multi-species project was the result of 3 years of planning. It will directly contribute to continued food security of Iñupiat and Inuvialuit communities in villages of the Alaskan and Canadian Arctic.

Western Arctic bowhead whales (also called Bering-Chukchi-Beaufort Sea bowhead whales) and Beaufort Sea beluga whales are critical subsistence and cultural resources for Iñupiat and Inuvialuit communities in the Arctic. To ensure these whale populations continue to thrive and support seasonal subsistence hunting, we need to understand how big they are.

NOAA and the Alaska North Slope Borough share responsibility for collecting data on bowhead whales. Both agencies provided considerable funding, staff support, and shared responsibility for planning and executing the project. The International Whaling Commission uses these data to determine bowhead whale harvest quotas(also known as strike limits).

NOAA and Fisheries and Oceans Canada also use data collected during the survey to assess the size and trend of the Beaufort Sea beluga whale population. Iñupiat and Inuvialuit communities hunt belugas and this population's summer range overlaps with the range of Western Arctic bowhead whales.

Bowhead and beluga whales seen together in the Beaufort Sea. Image captured during an aerial survey in the spring of 2011. Photo taken while working under authority of NOAA Fisheries Research Permit #14245. Credit: NOAA Fisheries & North Slope Borough / Vicki Beaver

Survey Design and Implementation

From July 28 to August 24, 2025, three teams of researchers assembled in the U.S. and Canadian Arctic to conduct the aerial surveys. One team was based in Deadhorse, Alaska, and used a NOAA-operated Twin Otter aircraft. The other two teams flew out of Inuvik, Canada, on Twin Otters contracted through Kenn Borek Air. Each team consisted of at least two pilots, three scientists, and a land-based engineer who prepped the planes and took care of any maintenance issues.

The NOAA Twin Otter aircraft stationed in Deadhorse, Alaska and the survey crew returned after a day of flying. Credit: NOAA Fisheries / Ron Pauley

Each evening, teams pored over weather forecasts-looking to see what the next day would bring. Storm systems, high winds, and fog presented obstacles. Transect lines on the far eastern and western ends of the survey area required fuel stops in remote villages. The amount of fuel needed changed based on flight plans and wind speeds. Often, teams adjusted plans the morning of the flight as conditions changed overnight.

Deadhorse survey team's morning pre-flight planning meeting on August 13, 2025. The team pored over weather forecasts and submitted required flight plans based on where there was good survey weather. Puzzles helped pass the time when the plane couldn't fly. Credit: NOAA Fisheries / Paul Hillman

The map below shows the survey areas, designed to cover the majority of the summer ranges for both Western Arctic bowhead and Beaufort Sea beluga whales. The teams were positioned strategically toward the center of their survey areas. Each team's goal was to fly all the transect lines in their survey area within the 28-day window. The two teams in Canada worked together to cover the larger area that extended into Amundsen Gulf.

Map of study area and proposed survey tracklines within each area. One team flew out of Deadhorse, Alaska, and two teams flew out of Inuvik, Canada. Credit NOAA Fisheries

Once on transect, the team was hyper focused on spotting whales. The pilots maintained a steady speed and altitude along the transect line, while two observers were dedicated to looking out of the bubble windows on either side of the aircraft. Over headsets, they communicated to the data recorder, who sat at a computer to enter data from the observers.

Observers Skyla Walcott and Tim Cole actively survey for bowhead and beluga whales, while Cynthia Christman records observation data on a laptop computer in the background. The observers use clinometers to measure the angle of the sighting. Knowing the altitude of the aircraft, they can calculate the horizontal distance of the whale from the aircraft, and record an accurate location of the animal. Credit: NOAA Fisheries / Paul Hillman

The data recorder annotated the location of the marine mammal sighting, the species, the number of animals, and their behavior. In some cases, the plane circled over the sighting to get a better look, confirm the species, and check for other individuals (like a calf). After circling, the observers got a short break while the pilots positioned the aircraft back on transect. Then, they got back on survey.

Together the three teams flew:

• 230 hours over more than 48,000 kilometers (30,000 miles)--that's more than one time around the Earth!!!
• 69.5 hours and 14,557 kilometers (9,045 miles) on transect-about 30 percent of the total

The remaining 160 hours were spent:

• Circling to confirm species identification and group size
• Traveling to and from the days' study area
• Running tests to evaluate the field of view for the observers-this helps determine how long they can detect animals from their bubble windows

Skyla Walcott surveys for marine mammals over the Beaufort Sea from a NOAA Twin Otter aircraft. The bubble window allows observers a much wider field of view. Credit: NOAA Fisheries / Paul Hillman

Survey effort in some areas was limited due to heavy sea ice, which made it difficult to see animals. When this happened, the team resurveyed some transects. Of the 14,557 kilometers (9,045 miles) flown on transect, 2,699 kilometers (1,677 miles) consisted of this sort of duplicate effort.

After preliminary review of the data, human observers recorded 1,177 marine mammal sightings (3,212 animals) including:

• 200 bowhead whale sightings (332 animals)
• 783 beluga whale sightings (2,377 animals)
• 194 other marine mammals sightings, such as other whale species and seals (503 animals)

Bowhead whale sightings (red stars) and transect effort (black lines). Credit: NOAA Fisheries Bowhead mother and calf pair swimming in the Beaufort Sea. Image captured during the 2025 aerial survey. Photo taken while working under authority of NOAA Fisheries Research Permit #25563-02. Credit: NOAA Fisheries & CICOES / Skyla Walcott Beluga whale sightings (white circles) and transect effort (black lines). Credit: NOAA Fisheries Beluga whales photographed during the 2025 aerial survey over the Beaufort Sea. This image was captured with the KAMERA camera system from the NOAA Twin Otter aircraft. Photo taken while working under authority of NOAA Fisheries Research Permit #25563-02. Credit: NOAA Fisheries & CICOES / Cynthia Christman

Maximizing Survey Accuracy and Estimating Abundance Trends

Each aircraft also included a camera system to capture images of bowhead and beluga whales. The NOAA Twin Otter based in Deadhorse, Alaska, carried a six-camera array. It collects very-high-resolution images directly below and slightly to the left and right of the path of the aircraft. The Twin Otters based in Canada each included a single Nikon camera.

Left: Cynthia Christman inspects the six-camera array pointed down through the belly of the NOAA Twin Otter aircraft. Right: looking down at the camera array during a survey over the Beaufort Sea. Credit: Paul Hillman / NOAA Fisheries

The imagery will be used to assess whether visual observers might have missed some animals. The imagery will also be added to the library of images, which can be used in future efforts to transition to using artificial intelligence to improve survey results.

We will analyze the counts of each species of whale in conjunction with the survey effort and sighting conditions to estimate the abundance of the Western Arctic bowhead and Beaufort Sea beluga populations. We will compare these estimates to estimates developed from the last survey in 2019. This will help us understand the population trend and determine whether these important whale populations are increasing, decreasing, or stable. The International Whaling Commission will use the resulting abundance and trend estimates to help determine the next Bering-Chukchi-Beaufort Sea bowhead whale quota or strike limit.

Success Through Collaboration

This project benefited from discussions with multiple representatives from subsistence hunting organizations, including:

• Alaska Eskimo Whaling Commission
• Inuvialuit/Canada Fisheries Joint Management Committee
• Hunters and Trappers Committees for multiple Inuvialuit Settlement Region coastal communities
• Inuvialuit Game Council

Support from the Inuvialuit/Canada Fisheries Joint Management Committee and the Department of Fisheries and Oceanswas key to the success of the project. The project was also a collaboration with the University of Washington's Cooperative Institute for Climate, Ocean, and Ecosystem Studies, which provided significant survey design expertise and field team leadership.

Operations in Canada were funded by the National Petroleum Reserve-Alaska Program (award 23-NPRA-212) made available through the State of Alaska Department of Commerce, Community, and Economic Development and NOAA Fisheries award for Community Directed Marine Mammal Research (award NA23NMF4690288).