AERIAL SURVEYS OF BELUGAS IN COOK INLET, ALASKA, AUGUST 2007

The National Marine Fisheries Service (NMFS) conducted an aerial survey of the beluga population in northern Cook Inlet, Alaska, 1-2 August 2007. The 13.1 hour survey covered the coastal areas north of Moose Point and the Native Village of Tyonek. 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 kt). The survey track paralleled the coast (1.4 km offshore) and crossed the Inlet the first day from just north of Moose Point to Tyonek, and the second day from Point Possession to Beluga River. Two flights were flown each day coinciding with the morning high tide and 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 number of calves. Video cameras used during past surveys (1999-2001 and 2002-2005) were paired with the high-definition video camera used in 2006-2007 to test for differences in video quality across years. 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 up river near the oxbow in the Little Susitna River was video-taped 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 mouth of the Little Susitna River (median count = 32 whales) for a total median count of 181 whales during the afternoon tide. Similar results occurred on 2 August, with belugas found dispersed across the Susitna delta and from the mouth to approximately 5 miles up the Little Susitna River during the morning high tide. 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. Belugas were not seen in Chickaloon Bay and 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).