AFSC/NMML: Small cetacean aerial survey in Alaskan waters, 1997-1999

Aerial surveys were conducted to produce abundance estimates for the three Alaska stocks of harbor porpoise. Surveys occurred from May to July 1997 for the Southeast Alaska stock, May to July 1998 for the Gulf of Alaska stock, and June to July 1999 for the Bering Sea stock. Two primary observers observed from bubble windows on the left and right side of the plane. A belly window observer with a view directly down along the trackline collected sightings that were matched to the side observers and used to estimate a correction factor for perception bias that was specific to harbor porpoise in Alaskan waters.

The primary objective was to collect line-transect data for abundance estimation, density, and distribution for the three stocks of harbor porpoise in Alaska waters and develop a correction factor for perception bias. The data was also used to estimate abundance, density, and distribution for Dall's porpoise throughout the study region.

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NOAA denies liability if the data are misused.

The data is available at http://data.nodc.noaa.gov/cgi-bin/iso?id=gov.noaa.nodc:0131991

There are no legal restrictions on access to the data. They reside in public domain and can be freely distributed.

User must read and fully comprehend the metadata prior to use. Applications or inferences derived from the data should be carefully considered for accuracy. Acknowledgement

of NOAA/NMFS/AFSC, as the source from which these data were obtained in any publications and/or other representations of these, data is suggested.

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All marine mammal species were recorded. Gaps in the survey occurred due to bad weather, particularly in the Gulf of Alaska south of Prince William Sound and south of the west end of the Alaska Peninsula. The data include possible doublecounts between observers. The belly window observer was an independent observer and matches between belly window and side window sightings were used to produce a correction factor for perception bias.

Data was edited each night after collection. Effort lines and sightings were plotted in ArcGis to assure accuracy of positional data.

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