STORY: Bill Fliris has lived in the remote village of Tanana, on the banks of Alaska's Yukon River, for the past 25 years. Each summer, he catches king salmon weighing 30 pounds or more. The fish feed himself and his family. But over the years, he's watched firsthand as fewer and fewer salmon returned from the sea to spawn. Scientists can't explain the declines, and clues are hard to come by. Now, it turns out that a salmon Fliris caught one day in 1986 may hold at least some of the answers.
FLIRIS: "My wife and I both noticed it. We had this particular fish that was different than the rest. This fish had a funny smell to it. Next year, though, we found a few more of those fish. The year following that, we were actually catching quite a few, and they all had the peculiar smell. It wasn't a rotten smell, but a vegetable smell."
At first, Fliris didn't make too much out of the odd-smelling fish. But within a few years, a quarter of the king salmon he caught each summer smelled funny. The fish had other problems as well.
KOCAN: "Indeed, these fish had Ichthyophonus."
Kocan says Ichthyophonus is common in fish all over the world. But it had only rarely shown up in Yukon River salmon. The parasite can be deadly to salmon, but isn't harmful to people. Last summer, using funds from the U.S./Canada Salmon Treaty, Kocan traveled to Alaska and examined king salmon caught from the river's mouth at the Bering Sea to its headwaters 1,500 miles upstream near Whitehorse, Yukon Territory, Canada.
KOCAN: "And what we found was that as they enter the river as they return to spawn, about 30 percent of the fish were infected. But they didn't show any signs of disease. As they moved up the river, by the time they got to Tanana, about 20 percent of the fish showed clinical signs of disease. And this is where Bill Fliris was seeing these sick fish. By the time they reached Circle and Dawson, all of the infected fish, for all practical purposes, showed clinical signs of disease. They had spots on their liver and in their meat and all over the place."
KOCAN: "It's probably not the major cause, but I think it could be a contributing cause. This is a hypothesis, but if we're correct that these fish are dying before they reach the spawning grounds, and they are not spawningthen this could mean that for at least the last ten years they may have had 30 percent fewer fish on the spawning grounds than they predicted."
This summer, Kocan and researchers from the United States Fish and Wildlife Service plan to examine salmon on the spawning grounds along the upper Yukon. Meanwhile, other questions remain, such as how the salmon became infected in the first place.
KOCAN: "We don't know. They could be infected either in freshwater before they leave, or they could be infected when they're at sea."
Not everyone believes disease is to blame for the crash. Gene Sandone, regional supervisor with the Alaska Department of Fish and Game, says chum salmon runs on the riverwhich have much lower rates of infectionalso have plummeted, and that salmon stocks throughout western Alaska are in trouble.
SANDONE: "We know for sure that the parent years of these salmon returningboth king and chumwere good. Now we're seeing extremely poor production from these parent years, and the one thing we can point to is poor ocean survival. We don't think it's a problem within freshwater. We think the problem is out in the ocean."
Sandone says because of the river's salmon declines, his agency may restrict king salmon harvests for subsistence food, and that there likely won't be any commercial fishing on the Yukon River this summer.
OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.
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Thanks to the following individuals for help preparing this script:
Bill Fliris, Yukon River fisherman
Dr. Richard Kocan, Professor
Gene Sandone, Regional Supervisor
Dan Albrecht, Executive Director
Jude Henzler, Executive Director
Dave Daum, Fisheries Biologist
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
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Related Web sites
Marine parasite infects Yukon River king salmon (Anchorage Daily News 1/28/04)
2004 Ichthyophonus Final Report to U.S. Fish and Wildlife Service Office of Subsistence Management