NMML Harbor Porpoise Aerial Survey, Kodiak Island, Replicate 3, 1992
National Marine Mammal Laboratory

Dataset credit

National Marine Mammal Laboratory


Primary contact Kimberly Goetz Duke University
Primary contact Janice Waite National Marine Mammal Laboratory
Data entry Ei Fujioka Duke University



On 6 July to 9 August 1992, as part of a larger study, Alaska harbor porpoise (Phocoena phocoena) abundance was investigated during an aerial survey off Kodiak Island. Employing a Twin Otter as the survey platform, the third of three identical sawtooth tracklines was flown at an altitude of 152.2 m (500 ft) and at an airspeed of 185 km/h. 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 off Kodiak Island was 1.41 (SE = 0.13) and 1.85 groups/100 km2 (SE = 6.03).


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.
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.

Supplemental information

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




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

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes in dataset provided

Attribute (table column)Description
Marine mammals90
Sea turtles0
Rays and sharks0
Other species0
Non spatial0
Non species0
Date, Begin1992-07-12
Date, End1992-08-09
Temporal prec.111111
Latitude56.03 - 58.75
Longitude-154.86 - -151.61
Coord. prec.5 decimal digits
Data typeAnimal sighting
EffortYES (ID: 163)
Traveled (km)1,745
Effort hours9
Sharing policy CC-BY-NC (Minimum)
Also availalbe from iOBIS
See metadata in static HTML
See metadata in FGDC XML
See download history / statistics