Results and evaluation of a survey to estimate Pacific walrus population size, 2006

Marine Mammal Science
By: , and 

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Abstract

In spring 2006, we conducted a collaborative U.S.-Russia survey to estimate abundance of the Pacific walrus (Odobenus rosmarus divergens). The Bering Sea was partitioned into survey blocks, and a systematic random sample of transects within a subset of the blocks was surveyed with airborne thermal scanners using standard strip-transect methodology. Counts of walruses in photographed groups were used to model the relation between thermal signatures and the number of walruses in groups, which was used to estimate the number of walruses in groups that were detected by the scanner but not photographed. We also modeled the probability of thermally detecting various-sized walrus groups to estimate the number of walruses in groups undetected by the scanner. We used data from radio-tagged walruses to adjust on-ice estimates to account for walruses in the water during the survey. The estimated area of available habitat averaged 668,000 km2 and the area of surveyed blocks was 318,204 km2. The number of Pacific walruses within the surveyed area was estimated at 129,000 with 95% confidence limits of 55,000 to 507,000 individuals. This value can be used by managers as a minimum estimate of the total population size.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Results and evaluation of a survey to estimate Pacific walrus population size, 2006
Series title Marine Mammal Science
DOI 10.1111/j.1748-7692.2010.00419.x
Volume 27
Issue 3
Year Published 2011
Language English
Publisher Society for Marine Mammalogy
Contributing office(s) Alaska Science Center Biology MFEB
Description 40 p.
First page 514
Last page 553
Country Russia, United States
Other Geospatial Bering Sea