Abstract:
From 4 to 13 August 1991, as part of a larger study, Alaska harbor
porpoise (Phocoena phocoena) 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 (500ft) and
at an airspeed of 100 kn. A single zigzag trackline was flown along the
... north
side of Bristol Bay, and the first of three identical saw tooth track lines 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 = .35) and 4.48
groups/100km2 (SE=1.38). 
Purpose:
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. During the present study, it was not fiscally possible to survey
all areas of the state in any one year. Accordingly, we selected sections of
the state to survey in consecutive years to maximize the likelihood of
including all of the animals for a particular area surveyed while minimizing
the likelihood of significant movement between areas among survey years.
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
