Bowhead Whale Census

Visual and acoustic monitoring to estimate the migrating whale population off the Alaskan coast

The ice-based bowhead whale census, initiated by NOAA in 1978 following the IWC’s 1977 moratorium on whaling, aims to monitor the migrating Bering-Chukchi-Beaufort population off Utqiaġvik (Point Barrow, Alaska) to establish subsistence hunting quotas. Early counts estimated fewer than 5,000 whales, prompting detailed monitoring to improve accuracy and enact required protections.

The census, a collaboration between Iñupiat, researchers and federal agencies funded by the local community of North Slope Borough, typically runs from April to late May, covering most of the bowhead migration period.

Ice-based observers use binoculars and a theodolite to track and record whale positions, speed, and distribution, ensuring sighting accuracy and avoiding duplicates. Every decade, the IWC requires an updated population estimate.

In 1984, the census expanded to include acoustic data collection. Hydrophones are placed in the water along the ice edge, enabling 24/7 monitoring used to estimate the number of whales within and beyond the area covered by the visual range (a semicircle from the ice’s edge with a 4 km radius), improving the accuracy of the overall population accuracy. Read more about Density Estimation.

A comprehensive census from 2009 to 2011, combining visual, acoustic, and aerial methods, produced a 2011 estimate of 16,892 whales with an annual growth rate of about 3.7%, reflecting a healthy, growing population. This outcome also protects Iñupiat food sustainability and cultural sovereignty. The next census is in the Spring of 2025.