Abstract:
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. 
Purpose:
A 3-year survey began in 1997 to complete a new abundance
estimate by 1999. This survey will also include an abundance estimate for
Dall's porpoise (Phocoenoides dalli). Once the 3 years of surveys are
completed, the data will be used to estimate annual abundance of harbor
porpoise and Dall's porpoise, which is one of the key pieces of information
needed to manage
... marine mammal-fishery interactions, as required under the
Marine Mammal Protection Act.
SUPPLEMENTAL INFORMATION: Inclement weather restricted the completion of the
entire planned survey. Survey lines were completed in Prince William Sound and
an adequate number of survey miles were completed offshore from Cape Suckling
west along the Kenai Peninsula, offshore of Kodiak Island, west to Sutwik
Island (Alaska Peninsula), and in Shelikof Strait. A total of 49.09 survey
hours were flown, with sightings of 69 harbor porpoise, 60 Dall's porpoise, 13
killer whales, 46 humpback whales, 25 fin whales, 1 Cuvier's beaked whale, 11
unidentified dolphins/porpoises, 31 unidentified whales, 21 harbor seals, 18
Steller sea lions, and 8 unidentified pinnipeds. These numbers do not include
the independent bubble window observer sightings.
CURRENTNESS REFERENCE: ground condition
SPATIAL REFERENCE INFORMATION -
GEODETIC MODEL
Horizontal Datum Name: D_WGS_1984
Ellipsoid Name: WGS_1984
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257224
