NMML Small Cetacean (coastal) Aerial Survey 1999, Gulf of Alaska

The National Marine Mammal Laboratory (NMML) conducted an aerial
survey for small cetaceans from 5 June to 4 July 1999 in Bristol Bay and along
southwestern Alaska Peninsula (out to the 1829 m (1000 fm) depth contour). A
total of 8,522 km were surveyed in a Dehavilland Twin Otter at 152.5 m (500 ft)
altitude and 185 km/hr (100 kts). Two overlapping sawtooth lines were designed
along the coastline of Bristol Bay. Both sides of each sawtooth were
approximately 37 km with a 46 km base. Large bays were also included in the
survey. Primary observers searched through bubble windows on the left and right
sides of the aircraft and reported sightings to a computer operator. To
estimate a perception bias correction factor for this study, an independent
observer was added at a belly window position to determine the number of
animals in the immediate vicinity of the trackline that were missed by the
primary observers. There were 215 sightings of harbor porpoise (260
individuals), 12 Dall's porpoise (24 individuals), and 16 Pacific whitesided
dolphins (170 individuals) while surveying tracklines. Additional cetacean
sightings included 12 gray whales (13 individuals), 18 humpback whales (29
individuals), 8 minke whales (13 individuals), and 3 killer whales (11
individuals).