title: Spatial and temporal occurrence of blue whales off the U.S. West Coast, with implications for management.
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.
authors: 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.
authors: Ladd M
authors: LM
authors: Irvine
authors: 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.
authors: Bruce R
authors: BR
authors: Mate
authors: 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.
authors: Martha H
authors: MH
authors: Winsor
authors: 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.
authors: Daniel M
authors: DM
authors: Palacios
authors: NOAA/NMFS/SWFSC/Environmental Research Division, Pacific Grove, California, United States of America.
authors: Steven J
authors: SJ
authors: Bograd
authors: Ecology and Evolutionary Biology, Long Marine Laboratory, University of California Santa Cruz, Santa Cruz, California, United States of America.
authors: Daniel P
authors: DP
authors: Costa
authors: Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, Solomons, Maryland, United States of America.
authors: Helen
authors: H
authors: Bailey
mesh_terms: D063147:Animal Distribution; D025041:Animal Migration; D000818:Animals; D050616:Balaenoptera; D056727:Endangered Species; D010140:Pacific Ocean