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Washington Sea Otter Surveys |
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The first comprehensive survey of the Washington sea otter was conducted in 1977. No surveys of the entire range
in Washington were conducted again until 1981. Surveys were done biennially from 1981 to 1989 and annually thereafter.
From 1977 to 1989, the population grew at near the maximum rate of increase for sea otter populations (17-20% per year).
Since 1989, however, the rate of increase appears to have declined to about 11% per year. In contrast, the sea otter
population in central California increased at an overall rate of about 4-5% annually until 1995, when a decline began
that continued through 1999. Results of the spring 2000 count indicate the decline in California may have ended (see
California Surveys).
Surveys are conducted annually during the first two weeks of July. The entire inshore area from Pt. Grenville (including Destruction Island) to the Pillar Point is surveyed. Surveys are conducted cooperatively by biologists of the Biological Resources Division of the United States Geological Survey, the Washington Department of Fish and Wildlife, and recently the Olympic Coast National Marine Sanctuary and the U.S. Fish and Wildlife Service. Most of the range is surveyed from a fixed-winged aircraft, but several ground stations are occupied each year. Protocol calls for two surveys per day over a period of three days. Thus, when conditions are favorable, six surveys of the entire range are completed. When weather conditions are unfavorable no counts are made. Because of the lower than expected count in 1998 and observations made by BRD researchers indicating some large groups of sea otters were resting offshore 1-2 kilometers, the protocol was modified in 1999 to include offshore transects. The survey total is calculated by summing the highest daily total for the south (Destruction Island to La Push) and north (La Push to Pillar Point) segments of the sea otter range. This assumes that there is little or no movement between the two segments during the survey period. Examination of survey data from years past and documented movements of instrumented sea otters by USGS researchers in Washington support this assumption. Large groups (more than 20) observed from the air are counted and photographed and recounted from the developed photographs. Counts from photographs are used when image quality is good.
Jim Estes Santa Cruz Field Station Long Marine Laboratory, UCSC 100 Shaffer Road Santa Cruz, CA 95060 Phone: (831) 459-2820 Fax: (831) 459-2249 Email: jim_estes@usgs.gov |
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