Aerial Surveys for Marine Mammals in Washington and British Columbia Inside Waters

This report summarizes information gathered by Cascadia Research under Contract #52ABNF-6-00092 funded by the National Marine Mammal Laboratory (NMML). The primary purpose of this contract was to determine the abundance of harbor porpoise based on aerial surveys in the inland waters of Washington and British Columbia. In addition to this objective, the contract was amended to add an analysis of harbor porpoise distribution in the San Juan Islands in relation to distance from shore and to provide a summary of harbor porpoise sightings and survey effort from previous surveys in 1991 based on international boundaries and new stock definitions contained in the recent harbor porpoise status assessment determination.

In order to promote wide disseminated of these results within the scientific community, we have prepared two manuscripts for submission to peer-reviewed scientific journals. This report includes drafts of both of these manuscripts plus supplemental information that is pertinent to the contract but not considered suitable for publication. In order to improve the manuscripts so that they were complete, we conducted additional analyses that were not originally anticipated.

These included:

• A more complete re-analysis of the 1991 survey results. In addition to changes in the study area boundaries, a number of other analysis components needed to be reworked to make them more directly comparable to the 1996 surveys results, including new definitions of
distance bins by clinometer angles, the testing of a full range of models for the distance function, use of a new correction factor, and a determination of Dall’s porpoise abundance
(see below).
• The determination of Dall’s porpoise abundance in addition to that for harbor porpoise for both the 1996 surveys as well as the previous 1991 surveys.
• A more complete examination of habitat criteria for harbor porpoise including expanding our evaluation to all region surveyed in 1996 (not just the San Juan Islands) and an evaluation of other habitat criteria including water depth and geographic sub-regions.

This contract report is organized as follows:

• The complete text, tables, and figures of a draft manuscript “Abundance estimates of harbor and Dall’s porpoise in Washington and British Columbia inside waters” for submission to the journal Fishery Bulletin. This publication includes a summary of survey effort and sightings
for both the 1991 and 1996 surveys.
• The complete text, tables, and figures of our draft manuscript “Distribution and habitat preferences of marine mammals in Washington and British Columbia inside waters” for submission to Fishery Bulletin.
• A section that contains supplemental information, primarily tables and figures, that are not contained in the above publications. This includes some of the items called for in the contract and amendments including details of the raw data structure and aspects of the habitat
analysis in the San Juan Islands.


Calambokidis, J., S.D. Osmek, and J.L. Laake. 1997. Aerial Surveys for Marine Mammals in Washington and British Columbia Inside WatersFinal report to the National Marine Mammal Laboratory, Seattle, WA 98115.

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