A recent study funded by the UC Davis School of Veterinary Medicine shows that northwest orca whales are accumulating contaminants from the salmon they eat.
The two-year study was led by Dr. Peter Ross of the Institute of Ocean Sciences in British Columbia and was funded by a grant from the Sea Doc Society, a program of the Wildlife Health Center at UC Davis. The study examined resident orca whales in the Puget Sound region spanning the coasts of British Columbia and Washington State.
“We knew from previous studies that these killer whales were among the most PCB contaminated marine mammals in the world,” Ross said. “Our aim in this investigation was to figure out the source of these chemicals.“
The study revealed that many of the contaminants are coming from salmon, which make up the majority of the orca’s diet.
“Orca whales are addicted to salmon,” Ross said. “It makes up about 90 percent of their diet. They especially like Chinook salmon which are the largest and heaviest species.“
A main focus of the study was investigating why southern populations of killer whales – those living between Seattle and Vancouver – had such higher levels of contaminants than northern populations. Ross said his study showed that the problem may have more to do with the type of salmon than actual contaminant levels in the water.
“Orcas primarily eat salmon for their fat content,” Ross said. “Northern populations of salmon tend to have much higher lipid content so the problem is likely that orcas in southern regions are simply having to eat more salmon to get the same amount of fat, and therefore are picking up more contaminants.“
One of the most significant findings of the study was that the salmon are not accumulating the contaminants from local waters, but are bringing them back from further out in the Pacific, said Dr. Joe Gaydos, regional director for the Sea Doc Society.
“This study is important because it shows us that this isn’t merely a local problem, but a global one,” he said. “It is really an issue of getting these contaminants out of the ecosystem.“
Gaydos said that studies similar to this one are very important to the future conservation of threatened species like orca whales.
“This study showed us that we really need to work with other countries to reduce these organic contaminants,” he said. “It is really important that before we take steps to protect these animals, we understand where the problems are coming from and how they can best be solved “
Kirsten Gilardi, assistant director for the Wildlife Health Center, said that one of the primary goals of the Sea Doc Society is getting the results of these studies to lawmakers.
“Our program really focuses in on the problems affecting the Puget Sound and figuring out where there are gaps in information,” she said. “We try to fund research that can answer some of these questions so that we can pass that on to the government and policy makers.“
Since its founding in 1999, the Sea Doc Society has awarded nearly $2 million to restore and maintain marine wildlife and ecosystem health. More information is available on their website at seadocsociety.org.
ERICA LEE can be reached at campus@theaggie.org.
