National Marine Mammal Laboratory (NMML)

Cetacean Assessment and Ecology Program

Cook Inlet Beluga Survey

Figure 2.  Beluga sightings recorded during six surveys of upper Cook Inlet, Alaska, 31 May to 9 June 2005.

Biologists from NMML, the NMFS Alaska Regional Office, and U.S. Army Fort Richardson (Anchorage) surveyed Cook Inlet, Alaska, for beluga whales (Delphinapterus leucas) 31 May to 9 June 2005, conducting 54.5 flight hours. Aerial survey procedures were kept consistent with protocol used since 1993, when these annual surveys began. An Aero Commander (a twin-engine, high-wing aircraft with bubble windows) was flown at an altitude of 244 m (800 ft) to survey coastal areas 1.4 km offshore around the entire inlet, including islands. Also, 1,363 km of offshore transects were flown. In total the survey covered approximately 28% of the surface area of Cook Inlet but 100% of the shoreline.

Paired, independent observers searched on the coastal (left) side of the plane, where virtually all beluga sightings occur, while a single observer was on the right. After finding beluga groups, a series of aerial passes was made so that each observer could make a minimum of four independent counts. This meant there were usually 16 counts of each group of whales each day. In addition, paired cameras captured images that will later be examined for precise counts that can be corrected for search time and applied to abundance estimates.

Beluga whales were found this year in the same areas they have been seen most years since 1993 (Fig. 2, above): the delta of the Big Susitna River, near the Little Su River, in Knik Arm, Turnagain Arm, and Chickaloon Bay. Besides the usual locations, some groups were seen along the shore of Fire Island. Similar to the distribution recorded over the past decade, all beluga groups seen in 2005 were in the northernmost parts of Cook Inlet, with no belugas seen south of Beluga River and Point Possession. The standard counting index, which is the summary of medians of counts of each whale group on each of the six survey days, was 192—comparable to annual index numbers since 1998 (ranging from 174 to 217).

By Dave Rugh and Kim Goetz


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AFSC Quarterly Research Reports April-June 2005