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Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management

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Title Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management
Names Irvine, Ladd M. (creator)
Mate, Bruce R. (creator)
Winsor, Martha H. (creator)
Palacios, Daniel M. (creator)
Bograd, Steven J. (creator)
Costa, Daniel P. (creator)
Bailey, Helen (creator)
Date Issued 2014-07-23 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by the Public Library of Science. The published article can be found at: http://www.plosone.org/.
Abstract Mortality and injuries caused by ship strikes in U.S. waters are a cause of concern for the endangered population of blue
whales (Balaenoptera musculus) occupying the eastern North Pacific. We sought to determine which areas along the U.S.
West Coast are most important to blue whales and whether those areas change inter-annually. Argos-monitored satellite
tags were attached to 171 blue whales off California during summer/early fall from 1993 to 2008. We analyzed portions of
the tracks that occurred within U.S. Exclusive Economic Zone waters and defined the ‘home range’ (HR) and ‘core areas’
(CAU) as the 90% and 50% fixed kernel density distributions, respectively, for each whale. We used the number of
overlapping individual HRs and CAUs to identify areas of highest use. Individual HR and CAU sizes varied dramatically, but
without significant inter-annual variation despite covering years with El Niño and La Niña conditions. Observed within-year
differences in HR size may represent different foraging strategies for individuals. The main areas of HR and CAU overlap
among whales were near highly productive, strong upwelling centers that were crossed by commercial shipping lanes.
Tagged whales generally departed U.S. Exclusive Economic Zone waters from mid-October to mid-November, with high
variability among individuals. One 504-d track allowed HR and CAU comparisons for the same individual across two years,
showing similar seasonal timing, and strong site fidelity. Our analysis showed how satellite-tagged blue whales seasonally
used waters off the U.S. West Coast, including high-risk areas. We suggest possible modifications to existing shipping lanes
to reduce the likelihood of collisions with vessels.
Genre Article
Access Condition http://creativecommons.org/licenses/by/3.0/us/
Identifier Irvine LM, Mate BR, Winsor MH, Palacios DM, Bograd SJ, et al. (2014) Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management. PLoS ONE 9(7): e102959. doi:10.1371/journal.pone.0102959

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