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PRI's Environmental News Magazine

Sick Salmon

Air Date: Week of June 20, 2008

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On the banks of the Yukon River, fisherman Pat Moore prepares king salmon to be hung in the smokehouse. It frustrates him when salmon show signs of “white spot disease," or Ich. “See, it’s all of the biggest, best-looking fish,” Moore says. “It breaks my heart.” (Photo: Rick Loomis/Los Angeles Times)

The Alaskan King Salmon fishery has long been the poster child for proper fisheries management, but, lately, salmon swimming the Yukon River face a threat much broader than overfishing: global warming. Los Angeles Times reporter Ken Weiss talks with Bruce Gellerman about rising river temperatures and "ich," the parasite that's infecting vast numbers of salmon.

Transcript

GELLERMAN: White Spot Disease is killing vast numbers of salmon along Alaska’s Yukon River. White Spot is caused by a parasite – appropriately named – “Ich”. Ich eats away at the internal organs and flesh of the fish. In some places along the Yukon River 30 percent of the salmon catch is infected with Ich. Kenneth Weiss—a Pulitzer Prize winning reporter for the Los Angeles Times—recently traveled to the area and he joins me from Los Angeles.

Ken – ich sounds really awful!

WEISS: It is awful, particularly to the fishermen who rely on the salmon that swim upstream in the Yukon. These are subsistence and traditional fishermen, Native Americans, who live along the river and have been fishing this way for decades. And they found that this fish that starts out with these little white pimples on the hearts of these salmon and then spreads to the flesh and makes them smell a bit like rotting fruit. And that’s become a real problem because they like to dry their fish in smokehouses and the whole batch can get tainted by this stuff. It really breaks the heart of these fishermen because it’s almost always the biggest and best looking fish, generally those large females that are carrying a lot of eggs needed to reproduce for successive generations. And they end up throwing away as much as 30 percent of their catch, feeding much of it to their dogs. Now these summer fishermen are also dog mushers in the winter so they have dozens and dozens of dogs but they end up throwing away so much fish it’s more than their dogs can eat.

GELLERMAN: So why are we seeing a problem now with Ich?


Ken Weiss covers the Pacific Coast and oceans for the Los Angeles Times. (Photo: Rick Loomis/Los Angeles Times)

WEISS: Well the fishermen first started noticing Ich in the late 1980’s and they didn’t know what was going on until they brought in an outside expert. There’s a fellow named Richard Kocan who’s a fish disease specialist at the University of Washington and he and his students started ruling out every possible reason that this disease was emerging and the only thing they found was it correlated with warmer water in the Yukon River. And the Yukon River’s water has been warming with an earlier break up of ice and particularly it’s been warming earlier in the season, in June. That’s when these Chinook salmon start their long migration to the headwaters about 2,000 miles away.

GELLERMAN: So the assumption is that global warming is heating the Yukon River and that’s causing this parasite to grow and thrive and that’s killing the salmon?

WEISS: That’s right. So the fish, unlike us warm blooded creatures, their body temperatures change with the ambient water, the water around them. So if they’re swimming in warmer water, it tends to accelerate the growth of this parasite as well as bacteria. It’s pretty much the same as when you take something out of your refrigerator and stich it on the counter too long and you find bacteria growing on it.

GELLERMAN: So are scientists expecting it to spread beyond the Yukon as things warm up?


On the banks of the Yukon River, fisherman Pat Moore prepares king salmon to be hung in the smokehouse. It frustrates him when salmon show signs of “white spot disease," or Ich. “See, it’s all of the biggest, best-looking fish,” Moore says. “It breaks my heart.” (Photo: Rick Loomis/Los Angeles Times)

WEISS: Yeah, since he’s been doing his work, it’s been found in salmon in rivers in British Columbia and in Kamchatka and elsewhere. It’s also showing up in some other types of fish such as the rockfish off of the Pacific Northwest, Oregon and Washington. Those are those bottom dwelling, great tasting fish that you see in the market often labeled incorrectly as red snapper or rock cod. And it showed up in other fish in the Puget Sound as well that we don’t eat. So one of the questions is: Is this a new arrival? Or are scientists simply finding it because they’re now looking for it? And there’s a debate about that. Ich, as it’s known, is what they call a cosmopolitan disease. It’s been around for a long time and it’s widespread but now it’s showing up in places that it’s never been found before and Doctor Kocan, at the University of Washington, he believes that salmon have been so closely monitored for so long that if it had been there, we would have seen it before.

GELLERMAN: Would we expect to see something like this, say, in the southern hemisphere, say South Africa or Chile?

WEISS: I think one of the things that these disease experts are seeing is that the whole geographical spread of disease is on the move with climate change. All sorts of different bugs, whether they’re bacteria or protozoa parasites or whatever can be limited by temperature. And when those temperature barriers fall, those bugs are quich to move into new ground. At the same time, I think there may be some places in the tropics where these bugs no longer persist—they just don’t thrive because it gets too hot. But I think we’re less likely to hear about those diseases that disappear as opposed to ones that emerge in new areas.

GELLERMAN: What, if anything, can be done to help these fish?

WEISS: Well, it’s difficult to know what to do. One thing that is an obvious implication for this research is to cut back on how many fish are taken through the commercial fishery. The commercial fisheries where we get our prized Alaskan salmon are usually down at the mouths of these rivers, it’s when the fish just start to swim upstream. Now those fish are, in the Yukon for instance, are infected with this parasite but the disease has not progressed. As the fish swim up the river, in warmer water, the disease progresses, and the idea is, if Doctor Kocan is right, that some of these fish are dying on the way up to their spawning grounds, that you need to cut back on the catch to compensate for that.

GELLERMAN: Ken Weiss is a Pulitzer Prize winning reporter for the LA Times. Ken, thanks a lot.

WEISS: Thank you.

 

Links

Check out the L.A. Times' multimedia coverage of sick salmon

 

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