Aerial Surveys of Beluga Whales (Delphinapterus leucas) in Cook Inlet, Alaska, June 2014

NOAA Fisheries has conducted aerial surveys of the beluga population in Cook Inlet, Alaska, each June, July, or both from 1993 to 2012, after which biennial surveys began in 2014. The current document presents survey results and subsequent analyses yielding an abundance estimate and population trend based on data collected during June 2014.

Surveys occurred June 3-12, 2014 (52 flight hours). All surveys were flown in twin-engine, high-wing aircraft (i.e., an Aero Commander) at a target altitude of 244 m (800 ft) and speed of 185 km/hour (100-120 knots), consistent with NOAA Fisheries' surveys of Cook Inlet conducted in previous years. Tracklines were flown 1.4 km from the shoreline along the entire Cook Inlet coast, including islands. Additionally, sawtooth pattern tracklines were flown across the inlet. These aerial surveys effectively covered 32% of the total surface area of Cook Inlet and 100% of the coastline. In particular, most of the upper inlet, north of the Forelands where beluga whales are consistently found, was surveyed six times (out of eight attempts).

Paired, independent observers searched on the coastal side of the plane, where virtually all beluga sightings occur, while a single observer searched on the inlet side. A computer operator/data recorder periodically monitored distance from the shoreline (1.4 km) with a clinometer (angle 10°). After finding beluga groups, a series of aerial passes allowed all observers to each make four or more independent counts of every group (i.e., typically 16 counts of each group conducted during eight passes). In addition, whale groups were video recorded for later analysis and more precise counts in the laboratory.