NMML Small Cetacean (coastal) Aerial Survey 1998, Gulf of Alaska

Researchers from NMML's Cetacean Assessment and Ecology Program
conducted the line transect aerial surveys for harbor porpoise and Dall's
porpoise from 27 May to 28 July 1998 in the Gulf of Alaska (offshore waters
from Cape Suckling to Unimak Pass), Prince William Sound, and Shelikof Strait.
Surveys were conducted from a NOAA Corps DeHavilland Twin Otter, flown at an
altitude of 152.5 m (500 ft) and an airspeed of 185 km/hr (100 knots). Sawtooth
lines were designed to cover the offshore waters from Cape Suckling to Unimak
Pass (offshore of Kodiak Island) and included lines extending 15 nmi seaward,
or to the 50 fathom line, whichever was farthest from shore and lines extending
to the 1,000 fathom line. In Shelikof Strait a series of zigzag lines were
designed between the Alaska Peninsula and Kodiak Island. Larger inlets and bays
were also included in the survey. The survey in Prince William Sound consisted
of two lines: one covering the central waters and one along the coast with
extensions into selected inlets. Two primary observers surveyed from a bubble
window on the left and right sides of the plane. An independent observer was
positioned in a belly window. This observer surveyed the trackline directly
below the plane to record animals missed on the trackline by the primary
observers.