Increased Harbor Porpoise Mortality in the Pacific Northwest, USA: Understanding When Higher Levels May be Normal

Authors

Jessica L. Higgins, Collective
Stephen A. Raverty, British Columbia Ministry of Agriculture
Stephanie A. Norman, Orca NetworkFollow
John Calambokidis, CollectiveFollow
Joseph K. Gaydos, University of California - DavisFollow
Deborah A. Duffield, Portland State UniversityFollow
Dyanna M. Lambourn, Washington Department of Fish and WildlifeFollow
James M. Rice, Oregon State UniversityFollow
Brad Hanson, Northwest Fisheries Science Center
Kristin Wilkinson, Office of Protected ResourcesFollow
Steven J. Jeffries, Washington Department of Fish and WildlifeFollow
Brent Norberg, NOAA Fisheries
Lynne Barre, NOAA Fisheries

Sponsor

Funding for stranding response and tissue analysis was provided by the John H. Prescott Marine Mammal Rescue Assistance Grant Program and the Marine Mammal Unusual Mortality Event Fund.

Published In

Diseases of Aquatic Organisms

Document Type

Article

Publication Date

7-23-2015

Subjects

Phocoena -- Behavior, Harbor porpoise -- Stranding -- Pacific Northwest, Harbor porpoise -- Mortality

Abstract

In 2006, a marked increase in harbor porpoise Phocoena phocoena strandings were reported in the Pacific Northwest of the USA, resulting in the declaration of an unusual mortality event (UME) for Washington and Oregon to facilitate investigation into potential causes. The UME was in place during all of 2006 and 2007, and a total of 114 porpoises stranded during this period. Responders examined 95 porpoises; of these, detailed necropsies were conducted on 75 animals. Here we review the findings related to this event and how these compared to the years immediately before and after the UME. Relatively equal numbers among sexes and age classes were represented, and mortalities were attributed to a variety of specific causes, most of which were categorized as trauma or infectious disease. Continued monitoring of strandings during 4 yr following the UME showed no decrease in occurrence. The lack of a single major cause of mortality or evidence of a significant change or event, combined with high levels of strandings over several post- UME years, demonstrated that this was not an actual mortality event but was likely the result of a combination of factors, including: (1) a growing population of harbor porpoises; (2) expansion of harbor porpoises into previously sparsely populated areas in Washington’s inland waters; and (3) a more well established stranding network that resulted in better reporting and response. This finding would not have been possible without the integrated response and investigation undertaken by the stranding network.

Description

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 Inter Research and can be found at: http://www.int-res.com/journals/dao/dao-home/

DOI

10.3354/dao02887

Persistent Identifier

http://archives.pdx.edu/ds/psu/18890

Citation Details

Huggins, J. L., Raverty, S. A., Norman, S. A., Calambokidis, J., Gaydos, J. K., Duffield, D. A., & ... Barre, L. (2015). Increased harbor porpoise mortality in the Pacific Northwest, USA: understanding when higher levels may be normal. Diseases Of Aquatic Organisms, 115(2), 93-102.