NMML Harbor Porpoise Vessel, SE Alaska, Summer 1993

National Marine Mammal Laboratory

In summer 1993, the Alaskan panhandle and Prince William Sound 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, few estimates of abundance exist. In 1991, the National Marine Mammal Laboratory initiated a 3 year 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, and
2) Establish a baseline for detecting changes in abundance through time, for analysis of trends.
The ability of the observers to sight porpoise was sensitive to environmental conditions. As expected, when conditions deteriorated the number of porpoises observed declined.

This dataset and associated effort data were updated on September 8, 2005. Those who downloaded them before that date should renew them.

Overview

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
dataset
lineno
dupl
date
event
time
dtime
beaufort
weather
portvis
starvis
shiphead
latdeg
latmin
dlat
londeg
lonmin
dlong
pdisshor
pdismet
sdisshor
sdismet
pobs
recorder
sobs
species
common
tsn	Species ITIS TSN
scientific
group
bowangle
reticles
numret
distshor
disshorm
estdisan
edismet
raddis
perpdis
dirtrav
observ
best
high
low
speed
comments
excluded
oid	Unique ID number (generated by SEAMAP)