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

Original provider:
National Marine Mammal Laboratory

Dataset credits:
National Marine Mammal Laboratory

Abstract:
From 4 to 13 August 1991, as part of a larger study, Alaska harbor porpoise (<i>Phocoena phocoena</i>) 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 (500 ft) and at an airspeed of 185 km/h. A single zigzag trackline was flown along the north side of Bristol Bay, and the first of three identical sawtooth tracklines 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 = 0.35) and 4.48 groups/100 km2 (SE = 1.38).