NMML Harbor Porpoise Aerial Survey, Cook Inlet, 1991

On 1 and 2 August 1991, as part of a larger study, Alaska harbor porpoise (Phocoena phocoena) abundance was investigated during an aerial survey throughout the coastal waters of Cook Inlet. A Twin Otter was used to fly a single sawtooth trackline across Cook Inlet at an altitude of 152.2 m (500ft) and at an airspeed of 100 kn. Line-transect methodology was used, and only those observations made during optimal conditions were analyzed. Density of harbor porpoises was calculated using line transect estimates based on perpendicular distances of sightings to the cruise track of the airplane. On average, porpoise group size and density for Cook Inlet was 1.33 (SE = .33) and .54 groups/100 km^2 (SE=.31).