Contaminated Salmon Make Unhealthy Meals for Killer Whales

February 12, 2009

Photo: killer whale rising out of water

Killer whales, or orcas, are being contanimated by chinook salmon that they
eat. The salmon are acquiring the contaminants, such as PCBs, in the ocean.

A new study funded by UC Davis shows how killer whales (orcas) in the
Pacific Northwest accumulate contaminants such as PCBs, which can reduce
their ability to fight disease and have healthy offspring.

The contaminants are coming from the chinook salmon that are the majority of
the whales' diet, said study lead author Donna Cullon of the Institute of
Ocean Sciences, Fisheries and Oceans of Canada. And the salmon are acquiring
the contaminants while at sea, not while in rivers -- a finding that could
help conservation efforts.

Cullon and colleagues tested young salmon as they headed to sea, and mature
salmon as they returned to rivers to spawn. They measured the fishes' levels
of persistent organic pollutants, including flame retardants, industrial
by-products, and organochlorine pesticides.

A particularly worrisome finding of the study was that the salmon eaten by
the southern population of resident whales (off Seattle, Wash., and
Vancouver, British Columbia) had much higher concentrations of pollutants
than those eaten by the northern resident population (off central and
northern British Columbia). While both populations are at risk, the southern
population is considered at greater risk and classified as endangered, while
the northern is classified as threatened.

The two-year study was conducted by American and Canadian scientists and
supported by a competitive grant from the SeaDoc Society, a program of the
Wildlife Health Center at the UC Davis School of Veterinary Medicine.

(The SeaDoc Society has funded nearly $2 million in grants to restore and
maintain marine ecosystem health in the North American Pacific region. Grant
applications for the 2010-2011 funding cycle will be due in fall 2009. More
information is online at:
http://www.seadocsociety.org/node/47#fundedresearch.)

The study, "Persistent Organic Pollutants in Chinook Salmon (Oncorhynchus
tshawytscha): Implications for Resident Killer Whales of British Columbia
and Adjacent Waters," is online at
http://www.allenpress.com/pdf/ENTC_28.1_148.pdf.