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Cetacean Assessment & Ecology Program

Beluga Whales in Northern Cook Inlet, Alaska, August 2007

Figure 2 map, see caption
Figure 2.  Click image to enlarge.

An aerial survey of the beluga population in Cook Inlet, Alaska, was conducted 1-2 August 2007. The 13.1-hour survey covered all coastal areas north of Moose Point and the Native village of Tyonek in the northern part of the inlet (Fig. 2). Consistent with NMFS surveys conducted since 1993, the August 2007 survey was flown in a high-wing, twin-engine aircraft (NOAA Twin Otter N56RF) at an altitude of 244 m (800 ft) and a speed of 185 km/hr (100 knots).

The survey track paralleled the coast (1.4 km offshore) and crossed the inlet from just north of Moose Point to Tyonek on the first day and from Point Possession to the Beluga River on the second day. Two flights were flown each day to coincide with the morning high tide and the afternoon low tide. The intent of the survey was to obtain high-resolution video of each beluga group to determine age structure (white relative to gray individuals and dark gray calves) and an index of calf numbers.

Despite extensive surveys of the northern inlet, belugas were found only in the Susitna delta. During the morning high tide on 1 August, belugas were dispersed and swimming in random directions across the delta from the Ivan River to the eastern tributary of the Susitna River, precluding us from acquiring any useable video or counts. A smaller group in tight formation traveling upriver near the oxbow in the Little Susitna River was videotaped and counted (median count = 27 whales). By the afternoon low tide, whales were found in three compact groups traveling along the edge of the mudflats near the mouth of the Ivan River (median count = 53 whales), the eastern tributary of the Susitna River (median count = 96 whales), and the mouth of the Little Susitna River (median count = 32 whales) for a total median count of 181 whales.

Similar results occurred on 2 August, with belugas found dispersed during the morning high tide across the Susitna delta and from the mouth to approximately 5 miles up the Little Susitna River. The afternoon low tide yielded two compact groups, one near the mouth of the Ivan River (median count = 88 whales) and the other near the Little Susitna River (median count = 53 whales), for a total median count of 141 whales. It was unusual that whales were not found in Chickaloon Bay or Knik Arm.

The daily median estimates (a quick index of relative abundance not corrected for missed whales) were on par with August 2006 counts (126 belugas on 16 August, 143 on 17 August) but were below counts made in August 2005 (236 belugas on 11 August, 277 on 12 August).

By Kim Shelden, Kimberly Goetz, and Julie Mocklin

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