Spatial and temporal occurrence of blue whales off the U.S. West Coast, with implications for management

Ladd M Irvine; Bruce R Mate; Martha H Winsor; Daniel M Palacios; Steven J Bograd; Daniel P Costa; Helen Bailey

doi:10.1371/journal.pone.0102959

Spatial and temporal occurrence of blue whales off the U.S. West Coast, with implications for management

PLoS One. 2014 Jul 23;9(7):e102959. doi: 10.1371/journal.pone.0102959. eCollection 2014.

Authors

Ladd M Irvine¹, Bruce R Mate¹, Martha H Winsor¹, Daniel M Palacios², Steven J Bograd³, Daniel P Costa⁴, Helen Bailey⁵

Affiliations

¹ Marine Mammal Institute, Department of Fisheries and Wildlife, and Coastal Oregon Marine Experiment Station, Oregon State University, Hatfield Marine Science Center, Newport, Oregon, United States of America.
² Cooperative Institute for Marine Ecosystems and Climate, Institute of Marine Sciences, Division of Physical and Biological Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America; NOAA/NMFS/SWFSC/Environmental Research Division, Pacific Grove, California, United States of America.
³ NOAA/NMFS/SWFSC/Environmental Research Division, Pacific Grove, California, United States of America.
⁴ Ecology and Evolutionary Biology, Long Marine Laboratory, University of California Santa Cruz, Santa Cruz, California, United States of America.
⁵ Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, Maryland, United States of America.

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.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animal Distribution*
Animal Migration*
Animals
Balaenoptera*
Endangered Species*
Pacific Ocean

Grants and funding

Funding for this research was provided by a variety of sources across 15 years including the Office of Naval Research (http://www.onr.navy.mil/), Tagging of Pacific Pelagics (http://www.topp.org/), the National Science Foundation (www.nsf.gov), the Oregon State University Marine Mammal Institute Endowment (mmi.oregonstate.edu), the Alfred P. Sloan Foundation (www.sloan.org), the Packard Foundation (www.packard.org), and National Geographic (www.nationalgeographic.com). Funding was also provided under the interagency NASA, USGS, National Park Service, US Fish and Wildlife Service, Smithsonian Institution Climate and Biological Response program, Grant Number NNX11AP71G (http://www.nasa.gov/topics/earth/features/climate_partners.html). Funding for OpenAccess provided by the University of California, Santa Cruz, Open Access Fund. While a number of the authors are employed by the Oregon State University Marine Mammal Institute, funding by the Marine Mammal Institute Endowment of some of the work presented here (typically in the form of matching funds) did not influence study design, data collection and analysis, decision to publish, or preparation of this manuscript. None of the other funding agencies influenced any aspects of this manuscript.