In fall 1991, Southeast Alaska, Cook Inlet, and Bristol Bay, were
surveyed for harbor porpoise (Phocoena phocoena) from the NOAA John N. Cobb
using line transect methodology. The shipboard platform was 28.36 m (93 ft) in
length with a bridge height of 4.27 m (14 ft). To obtain data on seasonal
movements of porpoise, a limited number of transects were made in areas of
known porpoise concentrations. ... When a sighting was made, the following
variables were recorded: time, angle, number of reticles to the sighting, radar
distance (nm) to the shoreline at the same angle of the sighting, the species,
the count of the porpoise seen (best, high, and low), and the animal(s)
direction of travel. Search effort was recoded by noting the time and location
of the ship at the beginning and end of each transect.
Although harbor porpoises, Phocoena phocoena, are known to occur
throughout Alaska waters (Fiscus et al. 1976; Leatherwood and Reeves 1978;
Lawry et al. 1982; Leatherwood et al. 1983), few estimates of abundance exist.
In 1991, the National Marine Mammal Laboratory initiated a 3-yr study on Alaska
harbor porpoises. The objectives of this program were to: 1) Obtain minimum
population estimates in ... coastal waters using line transect methodology with a
coefficient of variation for density estimates of less than 30% for each survey
area. 2) Establish a baseline for detecting changes in abundance through time,
for analysis of trends.
SUPPLEMENTAL INFORMATION: Note: This dataset and associated effort data was
updated on Sept 8, 2005. Those who downloaded them before that date should
renew them. The ability of the observers to sight porpoise was sensitive to
environmental conditions. As expected, when conditions deteriorated the number
of porpoises observed declined.
CURRENTNESS REFERENCE: ground condition
SPATIAL REFERENCE INFORMATION -
Horizontal Datum Name: D_WGS_1984
Ellipsoid Name: WGS_1984
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257224