NMML Harbor Porpoise Aerial Survey, Bristol Bay, Replicate 1, 1991

A Twin Otter was used as the survey platform. The surveys were flown at an altitude of 152.2 m (500ft) and at an airspeed of 100 kn.

A single zigzag trackline was flown along the north side of Bristol Bay, and the first of three identical saw tooth track lines was flown along the south side. 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.