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Pacific harbor seal, Phoca vitulina richardii, census in California during May-July 2002
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2003
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[PDF-2.27 MB]
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Description:An aerial photographic census of Pacific harbor seals (Phoca vitulina richardii) was conducted in California 22 May-1 July 2002 to document the number of seals hauled out during the molt period. To compensate for latitudinal differences in the timing of the molt, the state of California was divided into three sections and each section was surveyed on different dates. The three sections were: (1) Channel Islands and mainland coast of southern California from the U.S./Mexico border to Pismo Beach, (2) central California from Pismo Beach to Point Reyes and San Francisco Bay, and (3) northern California from Point Reyes to the California/Oregon border. Aerial photographic surveys at the Channel Islands and the mainland coast of southern California occurred during the high-low tide cycle in the afternoon on 22-25 May and the low-low tide cycle during the morning of 16 June. Surveys in central California and northern California occurred during the low-low tide cycle at tides under one foot on 16-17 June and 28 June-1 July, respectively. Color transparency photographs of harbor seals were taken with a 126-mm-format camera equipped with image motion compensation. The geographical position of each photograph was recorded by linking the camera to a computer and Global Positioning System (GPS). Three observers searched for hauled-out seals and photographed them, as the aircraft was flown over the coastline at 213 m (700 feet). A total of 467 haulout sites within the state of California was found during the surveys. At the Channel Islands there were 3,878 seals counted out of the water and 5 in the water near haulout sites. Along the mainland coast of California and San Francisco Bay there were 17,555 seals counted hauled out and 136 seals counted in the water near haulout sites. Statewide, a total of 21,433 seals were counted hauled out of the water and 141 seals were counted in the water. The mainland coast of California was stratified into nineteen 0.5 degree latitude segments with counts from the San Francisco Bay estuary making up the twentieth stratum. Stratum 37.50 to 37.99 had the most seals (n = 3,005), most seals per haulout site (n = 835), second highest number of haulout sites (n = 34), and third highest mean number of seals per haulout site ([mean] = 88.4). Of the eight Channel Islands in southern California, Santa Cruz Island had the most seals (n = l,085) and Santa Barbara Island the fewest (n = 15).
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Content Notes:Mark S. Lowry and James V. Carretta.
"September 2003."
System requirements: Adobe Acrobat Reader.
Mode of access: World Wide Web.
Includes bibliographical references (p. 7-8).
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Rights Information:Public Domain
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