We measured persistent organic pollutant (POP) concentrations in chinook salmon (Oncorhynchus tshawytscha) in order to characterize dietary exposure in the highly contaminated, salmon-eating northeastern Pacific resident killer whales. We estimate that 97 to 99% of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), and hexachlorocyclohexane (HCH) in returning adult chinook were acquired during their time at sea. Highest POP concentrations (including PCBs, PCDDs, PCDFs, and DDT) and lowest lipids were observed in the more southerly chinook sampled. While feeding by salmon as they enter some more POP-contaminated near-shore environments inevitably contribute to their contamination, relationships observed between POP patterns and both lipid content and δ13C also suggest a migration-related metabolism and loss of the less-chlorinated PCB congeners. This has implications for killer whales, with the more PCB-contaminated salmon stocks in the south partly explaining the 4.0 to 6.6 times higher estimated daily intake for ΣPCBs in southern resident killer whales compared to northern residents. We hypothesize that the lower lipid content of southerly chinook stocks may cause southern resident killer whales to increase their salmon consumption by as much as 50%, which would further increase their exposure to POPs.
On February 11, 2012, a juvenile female southern resident killer whale, L-112, stranded just north of Long Beach, Washington. The whale was in good nutritional condition. Autonomous passive acoustic recorders off the coasts of Washington, Oregon and California indicated that the L subgroup to which L112 belonged were near Pt. Reyes, CA on January 30, 2011, Ft. Bragg, CA on January 31, off Westport, WA on February 5, 2012 and near Newport, OR on February 20-21, 2012. These data and drift patterns for coastal Oregon and Washington waters suggested that L-112 had likely died off northern Oregon or in the Columbia River plume. An intensive series of diagnostic studies were initiated. Gross examination revealed extensive subcutaneous bruising on the dorsolateral aspects of the head, tracking to the throat and anterior insertion of the right pectoral fin. Microscopic assessment of sampled tissues was hindered due to advanced autolysis; there was generalized gas accumulation in most major organs. Nematodes (Crassicauda sp.) were evident in the right peribullar space with associated chronic inflammation. There was mild nonspecific and multisystemic chronic inflammation. Results from extensive bacterial, viral, molecular and toxicological tests were inconclusive. Head imaging studies (CT scans) and subsequent gross dissection revealed disruption of the cerebral hemispheres with marked accumulation of clear fluid and variably extensive hemorrhage. Examination of the axial skeleton revealed incomplete ossification of the dorsal vertebral process of C7 and Computed Tomography (CT) suggested that this defect was a congenital anomaly and likely unrelated to its death. PCR of feces indicated the presence of Chinook and halibut L-112’s diet. Anisakis sp. Cf. A. simplex also were identified in the stomach. Blunt trauma to the head and neck is the prime consideration for the immediate cause of death of this whale. In contrast to initial media reports, no military activities involving sonar or explosives were undertaken in the immediate vicinity of this animal, at the time of death. There was no gross indication of fisheries interaction. While the extensive evaluations were all consistent with trauma being the cause of death, the exact type or source of the traumatic injuries remains unknown.
Infectious diseases have the potential to play a role in the decline of threatened wildlife populations, as well as negatively affect their long-term viability, but determining which infectious agents present risks can be difficult. The southern resident killer whale, Orcinus orca, population is endangered and little is known about infectious diseases in this species. Using available reference literature, we identified 15 infectious agents (bacteria, viruses, and fungi) reported in free-ranging and captive killer whales, as well as 28 additional infectious agents reported in free-ranging and captive odontocete species sympatric to southern resident killer whales. Infectious agents were scored as having a high, medium, or low ability to affect fecundity or reproductive success, to cause disease in individual animals, and to cause epizootics. Marine Brucella spp., cetacean poxvirus, cetacean morbilliviruses, and herpesviruses were identified as high priority pathogens that warrant further study. Using identified pathogens to develop a standardized necropsy and disease testing protocol for southern resident killer whales and sympatric odontocetes will improve future efforts to better understand the impacts of priority and non-priority infectious agents on southern resident killer whales. This model can be used to evaluate potential infectious disease risks in other threatened wildlife populations.
In this newsletter:
Collaborative research: How can scientists, anglers, SCUBA divers and others best work together?
New initiative to support peer-reviewed publication.
Mapping Killer Whale foraging.
Decision on octopus protection.
Legislature funds derelict gear removal.
Jonna Mazet joins board of Morris Animal Foundation.
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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Slightly larger version: Download here. Credit should read: "Jeff Jacobsen, Humboldt State University Vertebrate Museum."