Global warming threatens Arctic whales

Scientists worried about spread of brucellosis


[foto] Beluga testicles, shown here below the animal’s penis, become bloated and filled with cysts from a disease called brucellosis, which appears to be on the rise in Arctic waters. Researcher Ole Nielson with the Department of Fisheries and Oceans says stress caused by climate change could be responsible for the four-fold increase in infected narwhal and beluga he’s observed over the last four years. (PHOTO COURTESY OF OLE NIELSON

Global warming could cause diseases to flourish in the Arctic’s whale populations, causing dramatic die-offs, warns a researcher with the federal Department of Fisheries and Oceans.

One such disease is brucellosis, which is caused by bacteria and exhibits itself as nasty cysts in the flesh of animals. The disease also causes fevers, weakness and other symptoms.

Over the last four years, Ole Nielson, a DFO biologist, has examined samples from diseased whales provided by hunter and trapper organizations around the Canadian Arctic.

“In some of the communities, half of the whales are... positive for brucellosis,” Nielson said on Tuesday. “It looks like a four-fold increase since 2002.”

Eating raw, infected meat could spread the bacteria to people.

So when hunters in Grise Fiord caught a narwhal several years ago with such cysts, they threw the carcass away, Nielson said. “That’s probably the smart move.”

Just as people are more susceptible to picking up the common cold or flu when they’re stressed out and tired, marine mammals may be more open to infections as they adapt to warmer ocean temperatures, Nielson suggests.

“It’ll put considerable stress on the animals. The ecosystem is changing,” he said.

That’s good news for bacteria and viruses, which could discover a wider range and more hosts to live off. But it’s bad news for marine mammals, and for people who hunt them.

Nielson said he’s particularly concerned of how brucellosis-infected whales have “huge cysts” in their genitals.

“I’m not a veterinarian, and I don’t know just how much this would affect reproduction, but this can’t be good for them, to have these huge cysts on their reproductive organs,” he said.

Nielson fears this could lead to a slow, steady decline in populations. But he also worries another disease, distemper, could cause far larger, and far quicker, die-offs in whale populations.

Just as distemper infects dogs, causing symptoms such as vomiting, fevers and seizures, a similar variety of the virus also infects marine mammals.

Distemper caused some 20,000 seals to die in the North Sea during the late
1990s, Nielson said. “Half of them actually died, in three or four months.”

Carriers of the disease could be none other than Canadian harp seals that had migrated to the area, Nielson said.

Several years later a different variety of distemper infected dolphins and porpoises in the same area.

Ring seals in the Canadian eastern Arctic are also known to carry the disease. “That’s a good thing,” Nielson said, explaining that because the animal is exposed to the virus, that means the seals also have some immunity – an ability to beat the virus.

But tests have shown no signs of past distemper infections with Arctic whale populations, he said, and he finds that worrying – because that means these whales should have little resistance to the disease. “I didn’t find any at all, that were even remotely positive,” he said.

Distemper has been found in pilot whales on the east coast of Canada, and common dolphins on the west coast. Warmer surface waters could bring these mammals farther north, just as fish like capelin are doing in the eastern Arctic, and salmon in the western Arctic.

If Arctic beluga and narwhal do become infected, Nielson predicts the animals could have their populations cut in half.

“You can expect die-offs of 50 per cent,” he said.

Such a drop could have a big impact on the quota levels set for populations already struggling, and strike a big blow to such beluga populations as the one in Ungava Bay, which is thought to be nearly extinct.

Some 72,000 to 144,000 belugas live in Canadian waters, according to DFO.

Not much can be done to prevent mammals from migrating, said Nielson. But more research, to keep track of the spread of diseases, could be important to accurately set hunting quotas.

Otherwise, “there wouldn’t be any warning until a year later, when there just aren’t any of them to hunt. That’s my worry,” Nielson said.

“They’re just going to disappear under the briny blue depths.”

Informant: binstock


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