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The application of GIS and spatiotemporal analyses to investigations of unusual marine mammal strandings and mortality events |
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| Authors: | Stephanie A. Norman Jessie Huggins Tim E. Carpenter James T. Case Dyanna M. Lambourn Jim Rice John Calambokidis Joseph K. Gaydos M. Bradley Hanson Deborah A. Duffield Sandra Dubpernell Susan Berta Matt Klope |
| Affiliation: | 1. Graduate Group in Epidemiology, W. Miller Laboratory, Vet‐Med: Pathology, Microbiology, Immunology, University of California, Davis, One Shields Avenue, Davis, California 95616, U.S.A. E‐mail: whaledoctor@gmail.com;2. Cascadia Research Collective, 218 1/2 W. Fourth Avenue, Olympia, Washington 98501, U.S.A.;3. Center for Animal Disease Modeling and Surveillance (CADMS), Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California at Davis, Davis, California 95616, U.S.A.;4. California Animal Health and Food Safety Laboratory, School of Veterinary Medicine, University of California, PO Box 1770, Davis, California 95617–1770, U.S.A.;5. Washington Department of Fish and Wildlife, 7801 Phillips Road SW, Lakewood, Washington 98498, U.S.A.;6. Oregon Marine Mammal Stranding Network, Marine Mammal Institute, Oregon State University, 2030 SE Marine Science Drive, Newport, Oregon 97365, U.S.A.;7. Cascadia Research Collective, 218 1/2 W Fourth Avenue, Olympia, Washington 98501, U.S.A.;8. University of California Davis, UC Davis Wildlife Health Center–Orcas Island Office, 942 Deer Harbor Road, Eastsound, Washington 98245, U.S.A.;9. NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, Washington 98112, U.S.A.;10. Department of Biology, Portland State University, PO Box 751, Portland, Oregon 97207, U.S.A.;11. Central Puget Sound Marine Mammal Stranding Network, Orca Network, 2403 North Bluff Road, Greenbank, Washington 98253, U.S.A. |
| Abstract: | In 2006–2007, an unusually high number of harbor porpoises (Phocoena phocoena) stranded along the Washington and Oregon coastlines. Spatiotemporal analyses were used to examine their ability to detect clusters of porpoise strandings during an unusual mortality event (UME) in the Pacific Northwest using stranding location data. Strandings were evaluated as two separate populations, outer coast and inland waters. The presence of global clustering was evaluated using the Knox spatiotemporal test, and the presence of local clusters was investigated using a spatiotemporal scan statistic (space–time permutation). There was evidence of global clustering, but no local clustering, supporting the hypothesis that strandings were due to more varied etiologies instead of localized causes. Further analyses at subregional levels, and concurrently assessing environmental factors, might reveal additional geographic distribution patterns. This article describes the spatial analytical tools applied in this study and how they can help elucidate the spatiotemporal epidemiology of other UMEs and assist in determining their causes. More than one spatial analytical technique should be used if the study objective is to detect and describe clustering in time and space and to generate hypotheses regarding causation of marine mammal disease and stranding events. |
| Keywords: | epidemiology harbor porpoise GIS Phocoena phocoena spatiotemporal analyses unusual mortality event |