| Abstract: | Sea otters (Enhydra lutris) occur in shallow coastal habitats and can be highly visible on the sea surface. They generally rest in groups and their detection depends on factors that include sea conditions, viewing platform, observer technique and skill, distance, habitat and group size. While visible on the surface, they are difficult to see while diving and may dive in response to an approaching survey platform. We developed and tested an aerial survey method that uses intensive searches within portions of strip transects to adjust for availability and sightability biases. Correction factors are estimated independently for each survey and observer. In tests of our method using shore-based observers, we estimated detection probabilities of 0.52-0.72 in standard strip-transects and 0.96 in intensive searches. We used the survey method in Prince William Sound, Alaska to estimate a sea otter population size of 9,092 (SE = 1422). The new method represents an improvement over various aspects of previous methods, but additional development and testing will be required prior to its broad application. |
| Genre: | Article |
| ProdID: | 87239 |
| Citation Author: | Bodkin, J. L.; Udevitz, M. S. |
| Citation Contributing Office: | Alaska Biological Science Center |
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| Citation Editor: | Garner, G. W.; Amstrup, S. C.; Laake, J. L.; Manly, B. F. J.; McDonald, L. L.; Robertson, D. G. |
| Citation End Page: | 26 |
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| Citation Language: | English |
| Citation Larger Work Title: | Marine mammal survey and assessment methods |
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| Citation Number Of Pages: | 14 |
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| Citation Phsyical Description: | 13-26 |
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| Citation Publisher: | A. A. Balkema |
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| Citation Search Results Text: | An aerial survey method to estimate sea otter abundance; 1999; Article; Report; Marine mammal survey and assessment methods; Bodkin, J. L.; Udevitz, M. S. |
| Citation Start Page: | 13 |
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| Citation Year: | 1999 |
| Type: | citation/reference |
| Text: | An aerial survey method to estimate sea otter abundance; 1999; Article; Report; Marine mammal survey and assessment methods; Bodkin, J. L.; Udevitz, M. S. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1999 00:00 -0600 |
| Publisher: | A. A. Balkema |
