Comparison of methods used to estimate numbers of walruses on sea ice

Marine Mammal Science
By: , and 

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Abstract

The US and former USSR conducted joint surveys of Pacific walruses on sea ice and at land haul-outs in 1975, 1980, 1985, and 1990. One of the difficulties in interpreting results of these surveys has been that, except for the 1990 survey, the Americans and Soviets used different methods for estimating population size from their respective portions of the sea ice data. We used data exchanged between Soviet and American scientists to compare and evaluate the two estimation procedures and to derive a set of alternative estimates from the 1975, 1980, and 1985 surveys based on a single consistent procedure. Estimation method had only a small effect on total population estimates because most walruses were found at land haul-outs. However, the Soviet method is subject to bias that depends on the distribution of the population on the sea ice and this has important implications for interpreting the ice portions of previously reported surveys for walruses and other pinniped species. We recommend that the American method be used in future surveys. Future research on survey methods for walruses should focus on other potential sources of bias and variation.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Comparison of methods used to estimate numbers of walruses on sea ice
Series title Marine Mammal Science
DOI 10.1111/j.1748-7692.2001.tb01007.x
Volume 17
Issue 3
Year Published 2001
Language English
Publisher Wiley
Contributing office(s) Alaska Science Center
Description 16 p.
First page 601
Last page 616
Country Russia, United States
Other Geospatial Chukchi Sea