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Cetacean Assessment & Ecology Program

Cook Inlet Beluga Survey, June 2007

After one of their airplanes disappeared near Anchorage, Alaska, in July 2006, Commander Northwest—the company that had provided aircraft for the NMFS Cook Inlet beluga surveys in Alaska since 1993—went out of business. When it became clear in May 2007 that the subsequent company, Northern Commanders, would not be able to provide a plane for the June 2007 beluga survey, we conducted exhaustive efforts to contract another private airplane.

The impending listing of Cook Inlet beluga whales as endangered under the Endangered Species Act (ESA) triggered strong requests for the survey from NOAA Administrator Vice Admiral Conrad Lautenbacher, NMFS Assistant Administrator Bill Hogarth, AFSC Science and Research Director Doug DeMaster, and Senator Ted Stevens. However, with only a few weeks until the proposed survey, all reasonable options for contracting private aircraft withered due to scheduling conflicts. Then, on 5 June, NOAA’s Aircraft Operation Center called to say they had managed to reschedule other projects in order to fly the beluga survey if we could arrive in Anchorage the next day. We did.

Accordingly, we conducted an aerial survey of the beluga population in Cook Inlet, 7-15 June 2007. The survey (47.2 flight hours) was flown in NOAA’s Twin Otter at an altitude of 244 m (800 ft) and speed of 185 km/hr (100 knots), consistent with NMFS’ surveys conducted each year since 1993. The study in June 2007 included one or more surveys of coastal areas (flown 1.4 km offshore) around most of the inlet and 1,342 km of transects across the inlet, effectively searching 25% of Cook Inlet and 71% of the coastline.

figure 1 map, see caption
Figure 1.  June 2007 daily beluga sightings in Cook Inlet.  Each symbol represents a group of beluga whales.

Paired, independent observers searched on the coastal (left) side of the plane, where virtually all beluga sightings occur, while a single observer and computer operator/data recorder were on the right side of the plane. After finding belugas, multiple aerial passes were made with paired observers doing four or more independent counts of each group.

Daily median counts made on seven different days ranged from 64 to 126 belugas in the Susitna delta (between the Beluga and Little Susitna rivers), 0 to 9 belugas in Knik Arm, and 8 to 60 belugas in Turnagain Arm and Chickaloon Bay (including whales seen north of Point Possession) (Fig. 1 above). Belugas were not observed in lower Cook Inlet, which has been typical of the annual surveys.

In June 2007, the highest daily median estimate, used here as an index for relative abundance (not corrected for effort nor for estimates of missed whales), was 224 belugas. This is below index counts for survey years prior to 1998 (305 belugas in 1993, 281 in 1994, 324 in 1995, 307 in 1996, and 264 in 1997) but higher than index counts made during the past 9 years (193 in 1998, 217 in 1999, 184 in 2000, 211 in 2001, 192 in 2002, 174 in 2003, 187 in 2004, 192 in 2005, and 153 in 2006).

By Dave Rugh, Kim Goetz, and Julie Mocklin

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