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

From 4 to 13 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 Bristol Bay. 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. On average,
porpoise group size and density for Bristol Bay was 1.17 (SE = .35) and 4.48
groups/100km2 (SE=1.38).