New study: Tainted salmon poisoning orcas
VANCOUVER, British Columbia (AP) - Resident killer whales in Puget Sound and off the west coast of North America are being poisoned by eating salmon laced with toxic PCBs, according to a study on the dwindling orca population.
Researchers in British Columbia found enough polychlorinated biphenols other man-made pollutants in the whales' main food - chinook salmon - to jeopardizing the large orcas.
The levels of PCBs in the salmon are relatively low, but even in small amounts there was enough to pose a significant risk, said Peter Ross of the Institute of Ocean Sciences in Sydney on Vancouver Island.
Ross says whales are particularly sensitive because they eat massive amounts of fish over a long life - killer whales can live for 80 or 90 years - creating a massive buildup of toxins.
That means the whales, particularly the southern resident population, have become some of the most contaminated marine mammals in the world.
"Killer whales are long-lived, top-of-the-food-chain animals. They have small, isolated populations. They have very large habitat needs," said Ross, supervising researcher on the study published in the current issue of the journal Environmental Toxicology and Chemistry.
"If we're trying to protect 84 animals in an area where we've got 8.5 million people, we've got a bit of work to do."
Northeast Pacific resident killer whales are divided into two populations.
The northern population, about 200 whales living off Vancouver Island and northern British Columbia, is listed as threatened under Canadian law legislation.
The southern population, 84 animals off southern British Columbia and Washington state, are listed as endangered under Canadian and U.S. law.
The latest study followed one in 2000 that found dangerous levels of pollutants which can damage the whales' immune systems, affect reproduction and lead to developmental abnormalities.
The earlier study found southern whales had four times the amount of toxins such as PCBs - an industrial chemical that has been banned in North America since the late '70s - as their northern counterparts. It wasn't clear where the whales were picking up the toxins until now.
Southern resident whales are eating salmon from waters, especially Puget Sound, that have high levels of PCBs. Salmon in those regions tend to have less fat as they return to coastal streams to spawn, so the whales eat more of them.
The study appears to confirm that contaminated whales are getting the chemicals from salmon, which should inform policy-makers in Canada and the U.S. as they try to protect the iconic orcas, Ross said.
"We were already assuming what was going on or taking steps to mitigate or manage (the effects of the pollutants)," says Ross. "There are things currently underway to try to reduce noise and disturbance, increase salmon productivity, and reduce chemical contamination. Some of these will take a long time to bear fruit."
Even so, Ross said there is reason to be optimistic.
In more than 30 years since PCBs have been banned in Canada and the U.S., contamination levels in killer whales have dropped by 250 per cent, Ross said.
"While we still have extraordinarily contaminated killer whales, things are better," he said. "We expect them to continue to get better."
Researchers in British Columbia found enough polychlorinated biphenols other man-made pollutants in the whales' main food - chinook salmon - to jeopardizing the large orcas.
The levels of PCBs in the salmon are relatively low, but even in small amounts there was enough to pose a significant risk, said Peter Ross of the Institute of Ocean Sciences in Sydney on Vancouver Island.
Ross says whales are particularly sensitive because they eat massive amounts of fish over a long life - killer whales can live for 80 or 90 years - creating a massive buildup of toxins.
That means the whales, particularly the southern resident population, have become some of the most contaminated marine mammals in the world.
"Killer whales are long-lived, top-of-the-food-chain animals. They have small, isolated populations. They have very large habitat needs," said Ross, supervising researcher on the study published in the current issue of the journal Environmental Toxicology and Chemistry.
"If we're trying to protect 84 animals in an area where we've got 8.5 million people, we've got a bit of work to do."
Northeast Pacific resident killer whales are divided into two populations.
The northern population, about 200 whales living off Vancouver Island and northern British Columbia, is listed as threatened under Canadian law legislation.
The southern population, 84 animals off southern British Columbia and Washington state, are listed as endangered under Canadian and U.S. law.
The latest study followed one in 2000 that found dangerous levels of pollutants which can damage the whales' immune systems, affect reproduction and lead to developmental abnormalities.
The earlier study found southern whales had four times the amount of toxins such as PCBs - an industrial chemical that has been banned in North America since the late '70s - as their northern counterparts. It wasn't clear where the whales were picking up the toxins until now.
Southern resident whales are eating salmon from waters, especially Puget Sound, that have high levels of PCBs. Salmon in those regions tend to have less fat as they return to coastal streams to spawn, so the whales eat more of them.
The study appears to confirm that contaminated whales are getting the chemicals from salmon, which should inform policy-makers in Canada and the U.S. as they try to protect the iconic orcas, Ross said.
"We were already assuming what was going on or taking steps to mitigate or manage (the effects of the pollutants)," says Ross. "There are things currently underway to try to reduce noise and disturbance, increase salmon productivity, and reduce chemical contamination. Some of these will take a long time to bear fruit."
Even so, Ross said there is reason to be optimistic.
In more than 30 years since PCBs have been banned in Canada and the U.S., contamination levels in killer whales have dropped by 250 per cent, Ross said.
"While we still have extraordinarily contaminated killer whales, things are better," he said. "We expect them to continue to get better."