[MARMAM] New paper on harbor seals

Thomas Jefferson sclymene at aol.com
Mon Jun 21 13:58:14 PDT 2021

Dear MARMAM,  My co-authors and I are pleased to announce the publication of our new paper on harbor seals in Washington State, USA:
Estimating the stock size of harbor seals (Phoca vitulina richardii) in the inland waters of Washington State using line-transect methods
Thomas A. Jefferson, Mari A. Smultea, Eric J. Ward, and Barry Berejikian

Harbor seals (Phoca vitulina richardii) in the inland waters of Washington were reduced by
predator control programs in the twentieth century, but stocks have rebounded since being
protected in the 1970s. Three management stocks are recognized, but there is little information
on their current abundance. We conducted 38,431 km of aerial line-transect surveys
throughout the range of these stocks in 2013–2016, sighting a total of 4,678 groups of harbor
seals. Line-transect analysis with Beaufort sea state as a covariate provided estimates
of the number of seals in the water. We then incorporated tagging data from 15 instrumented
seals to develop correction factors, both for seals missed in the water while diving, and
those that were on shore. Tagging data were modeled with generalized linear mixed models
to provide estimates of the proportions diving and hauled out. After applying these correction
factors, we estimated that the Hood Canal stock contained 1,368 seals (CV = 16.8%), the
Southern Puget Sound stock contained 1,976 seals (CV = 20.5%), and the Washington
Northern Inland Waters stock contained 7,513 seals (CV = 11.5%). This study presents a
non-traditional approach to estimating the size of Washington inland waters harbor seal
stocks, which may also be applicable to other species for which survey and tagging data are available.
The paper is open-acces and can be downloaded from this link:
Best wishes,Tom Jeffersonsclymene at aol.com
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