June 5, 2013 - for immediate release
Dr. Joe Gaydos, SeaDoc Society: 360.376.3910
Dr. Stephen Raverty, British Columbia Ministry of Agriculture 604.556.3026
Dr. Michelle Barbieri, NOAA Fisheries 443.834.8612
Dr. Brad Hanson, NOAA Fisheries 206.860.3220
Efforts to learn more from stranded killer whales are working
In a first-of-its-kind study published last week in the journal Marine Mammal Science, researchers analyzed North Pacific killer whale strandings dating back to 1925.
“This was a herculean effort to learn more about one of the ocean’s top predators,” says lead author Michelle Barbieri, a former SeaDoc scientist and currently the lead veterinarian for the Hawaiian Monk Seal Research Program. “We could not have done this without the collaboration of dozens of killer whale scientists from around the world who provided stranding and population data from Washington State, Oregon, California, Alaska, Hawaii, British Columbia, Mexico, Japan and Russia.
The final report noted that while orcas are some of the most widely distributed whales on earth, very few dead ones are ever found. Over the last two decades, an average of just 10 a year have been discovered stranded across the entire North Pacific Ocean. The study determined that 88% of all reported killer whale strandings are fatal while only 12% make it off the beach alive. It’s those dead whales, though, that can provide critical clues to the species’ overall life history, genetics, health and causes of mortality. With such limited opportunity to do comprehensive sampling and studies, the study’s authors noted the disturbing fact that, until recently, less than 2% of those dead killer whales were thoroughly examined.
“Each stranded orca should be viewed as a unique opportunity to enhance our understanding of this magnificent species,” says co-author and veterinary pathologist Stephen Raverty. To maximize the science gathered from each stranding, Raverty and Joe Gaydos, SeaDoc Director and another of the paper’s co-authors, created a standardized killer whale necropsy protocol in 2004. The analysis of strandings since then has shown that the protocol -- along with funding from the US National Marine Fisheries Service and Canadian Department of Fisheries and Oceans dedicated to southern resident killer whale recovery – has boosted the collection of complete data from killer whale strandings. Where traditionally only one in fifty would be analyzed, one in three now get a full work-up.
While this new study was designed to look at stranding trends and did not evaluate the causes, necropsies on beached orcas have shown that they absorb extremely high loads of manmade toxins, suffer from infectious diseases, and in the case of fish-eating populations, depend primarily on severely depleted salmon stocks. With the standardized protocol now in place providing much more complete data on strandings, researchers are getting a clearer picture of killer whale life and death.
“As apex predators and flagship conservation species, killer whale strandings are sad events,” says Gaydos, “but this paper confirms that if we make every effort to understand why the stranding occurred, we will ultimately improve the fate of the species.”
To view the paper, see below.
The SeaDoc Society is about people and science healing the sea. It is a program of the Wildlife Health Center, a center of excellence at the UC Davis School of Veterinary Medicine.
Barbieri, Michelle M., S. Raverty, M.B. Hanson, S. Venn-Watson, J.K.B. Ford, J.K. Gaydos. 2013. Spatial and temporal analysis of killer whale (Orcinus orca) strandings in the North Pacific Ocean and the benefits of a coordinated stranding response protocol. Marine Mammal Science, DOI 10.1111/mms.12044
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Images for press use:
Slightly larger version: Download here. Credit should read: "Jeff Jacobsen, Humboldt State University Vertebrate Museum."