Ice-Based Census

Principal Investigators J. Craig George, Ph.D.
Collaborators Judy Zeh (University of Washington), Geof Givens (Colorado State University), Chris Clark (Cornell University), Robert Suydam


The ice-based bowhead whale census began in 1978 by NOAA after the moratorium imposed by the International Whaling Commission (IWC) in 1977 on subsistence whaling of bowhead whales. NOAA had conducted preliminary ice-based surveys before 1978. The IWC’s decision on a moratorium was based on NOAA’s report that there were fewer than 1000 bowhead whales in the Bering-Chukchi-Beaufort (BCB) stock and on an increasing number of strikes. The census effort was proposed to obtain a more accurate population count of the bowhead whales. The Bowhead Census project was transferred from NOAA to the AEWC in 1981 and then to the NSB Department of Wildlife Management (at that time, the department was named the Environmental Protection Office or EPO) in 1982.

The visual census occurs from about 15 April to the end of May. The census period captures most of the migration but some whales pass before and after the census period. A theodolite is used to position whales in the lead once they are spotted by eye or with binoculars. Three observers work 2-4 hour watches during daylight hours (which is 24 hours roughly by the first week of May). Whale positions are plotted to help determine if the sightings are new or duplicated. Also offshore distribution, whale speed and other statistics are estimated. A new abundance estimate is required by the IWC at least every 10 years.

The 2001 ice-based census estimate was 10,470 (or between 8,100 and 13,500 with 95% confidence intervals) bowhead whales (see George et al. 2004), and an updated estimate was obtained via aerial surveys and photogrammetry in 2004. The graph below shows the population trend as of 2004 when the calf production reached 10.4% and the growth rate was estimated at 3.4%, indicating a healthy, growing population of about 12,634 (or between 7,900 and 19,700 with 95% confidence intervals) (see Koski et al. 2010) bowhead whales in the Bering-Chukchi-Beaufort (BCB) stock.

A new ice-based census (combined with aerial surveys and photogrammetry) was carried out in the springs of 2009, 2010, and 2011. The 2011 bowhead whale census was the most successful ever conducted with full visual, acoustic and aerial coverage of the bowhead migration. After two years of intensive analysis, the new 2011 abundance estimate for the Bering-Chukchi-Beaufort Seas stock of bowhead whales was presented at IWC 2013 in Korea. The estimate is 16,892 with a “margin of error” between 15,704 to 18,928 whales. This stock continues to grow at about 3.7% annually, which indicates that the health status of this population is very good.

This is a drawing of the bowhead whale census camp in 1984. You can see the two perches placed on pressure ridges on either side of the drawing, two small camps, and one main campsite (drawing: Craig and Jean Craighead George)

Tim Obritschkewitsch looks through the theodolite to accurately position the location of a bowhead whale sighted in the lead Salomi Akpik, Kate Stafford, Perry Anashugak and Jason Herreman looking for whales from the perch in 2009

Population Estimates From 1978 to 2004

This graph shows the population trend for the Bering-Chukchi-Beaufort stock of bowhead whales obtained from census efforts between 1978 and 2001. The 2001 census estimate was 10,470 whales (or 8,100-13,500 with 95% confidence intervals). The population growth rate was estimated at 3.4% (or 1.7-5.0% with 95% confidence intervals) (Source: George et al. 2004). The graph below also includes an estimate from the 2004 photogrammetry work of 12,600 whales (95% confidence intervals 7,900 – 19,700).

The BCB bowhead whale population trend from 1978-2004. The circles indicate ice-based census estimates. The bars on the census estimates are the 95% confidence intervals (Source: Craig George)

Population Estimate From 2011

Census coordinators, Craig George and Robert Suydam, Director Taqulik Hepa and Deputy Director Harry Brower, Jr., and all from the NSB-DWM thank the whaling community, AEWC, NSB, NOAA, BP and other entities who have supported our research over the years. Maintaining the bowhead quota is one of our main goals, and this new estimate will help considerably with future quota renewals.

Bowhead Population Estimate 2011

Scenes From the Perch

Bowhead whale breaching in the lead system (photo: Kate Stafford) Splashing in the open lead near Barrow in the spring (photo: Peter Lourie)

Scenes From the Census Camp

On the way to the perch, crossing an active crack in the landfast ice. Note: this is a “good crack” at the beach head and is caused by tidal activity This photo shows a typical tent set up at the census camp. Note: freight sled set alongside the tent for hauling camp
This outhouse was carved out of a piece of multi-year ice at the census camp This ‘bear alarm’ is used to alert the census crew if a polar bear enters the campsite. Note: the rat trap mechanism at the heart of the device, which was designed by Dave Ramey


Banner photo credit: Lisa Baraff

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