2006-2008 Aerial Surveys of Endangered Whales in the Beaufort Sea

March 07, 2006

This report describes field activities and data analyses for aerial surveys of bowhead whales (Balaena mysticetus) conducted during fall 2006 (2 September – 16 October), fall 2007 (3 September – 10 October), and fall 2008 (5 September – 18 October) in the Beaufort Sea, between 140°W and 158°W, south of 72°N and north of the Alaskan coastline.

During September and October 2006-2008, ice cover was extremely light, with historic minimum summer sea ice retreat observed in 2007 and 2008.

In 2006, a total of 27 survey flights were attempted. There were 124 sightings of 406 bowhead whales. Additionally, 22 gray whales (Eschrichtius robustus), 525 belugas (Delphinapterus leucas), 59 bearded seals (Erignathus barbatus), 407 ringed seals (Pusa hispida), and 77 polar bears (Ursus maritimus) were observed. Total flight time was 90 hours, which included 56 hours of on transect survey effort.

Median distance from locations of sightings of bowhead whales in 2006 to a normalized shoreline was 34.3 km (range = 4-92 km) in the East Region, and 39.2 km (range = 3-74 km) in the West Region. Median depth at sightings was 44 m (range = 8-1,868 m) in the East Region, and 32 m (range = 7-204 m) in the West Region. Compared with other light ice years, sightings were significantly farther from shore and in deeper water in both the East and West Regions. The more seaward locations of bowhead whales may have been due to the presence of grounded ice in the East Region in September. Sightings in September 2006 in the East Region were significantly farther from shore and in deeper water than sightings in October. There was no statistically significant difference in the West Region between September and October.

In 2007, a total of 21 survey flights were attempted. There were 144 sightings of 409 bowhead whales. Additionally, 20 gray whales, 117 belugas, 106 bearded seals, 56 Pacific walruses (Odobenus rosmarus), 1,732 ringed seals, and 83 polar bears were observed. Total flight time was 93 hours, which included 36 hours of on transect survey effort.

Median distance from locations of sightings of bowhead whales in 2007 to a normalized shoreline was 21.8 km (range 1-74 km) in the East Region and 25.7 km (range 15-35 km) in the West Region. Median depth at sightings was 34 m (range 14-403 m) in the East Region and 22.5 m (range 12-35 m) in the West Region. Compared to other light ice years, sightings were significantly closer to shore and in shallower water in the East Region, but there was no significant difference in the West Region (sample size was very small in 2007 in the West Region). When non-migrating whales (feeding, milling, or resting whales) were removed from the central tendency analysis for all light ice years, bowhead whale sightings in the East Region were in significantly shallower water in 2007 than in previous light ice years, although distance from shore was not significantly different.

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Last updated by Alaska Fisheries Science Center on 03/12/2019

Research in Alaska Whales Aerial Surveys of Arctic Marine Mammals