Research Hints Dam
by Michael Milstein
For years, the massive hydroelectric dams on the Columbia and Snake rivers have been blamed for killing young salmon on their downriver migration to the ocean.
But a striking new study released Monday found that for some endangered salmon and steelhead stocks, just as many young fish survive their journey through the Snake and Columbia dams as survive a similar trip down Canada's Fraser River, which has no dams.
Even longtime fish biologists were flabbergasted by the finding. They figured fish would have an easier time in rivers without dams than those with dams. But even the authors of the study, including scientists based at Oregon State University, disagree over the meaning of the results and whether they indicate that Columbia dams are not as harmful to fish as long thought.
The conflict illustrates how differently scientists themselves can interpret the same data and underscores the maxim that science often raises more questions than it answers.
"This is what science is about," said Carl Schreck, an author of the paper who is a U.S. Geological Survey scientist and professor at OSU. "It's about solving disagreements."
The disagreement was highlighted in efforts by the peer-reviewed journal PLoS Biology, published by the Public Library of Science, to publicize the paper with the title, "Dams Make No Damn Difference to Salmon Survival."
Oregon scientists who contributed to the study said that's misleading and leaps to premature conclusions. They said the research may reflect poor survival of fish in the Fraser River, which has been increasingly degraded by pollution and development, as much as it does improved fish survival on the Columbia.
Schreck said his first reaction to the results was, "Maybe the Fraser really is in trouble."
But David Welch, a private-sector Canadian scientist who is the paper's lead author, said the results do suggest that the millions of dollars spent on making the Columbia and Snake dams friendlier to fish are paying off.
"What we're saying is that with the work that has been done, the survival seems to have been brought back up to the level of an adjacent river system that doesn't have dams," he said. "We're not seeing a direct effect of the dams that's large, which is what we always assumed we would have."
He said the message of the research "is not that dams are OK." But it does signal that conditions on the Columbia are improving and that steps taken by federal agencies have helped counter the harm of dams.
For instance, agencies such as the Bonneville Power Administration fund efforts to control predatory fish in the Columbia River. That might offset the effects of dams by reducing pressure on protected salmon the predators might otherwise feast on, he said.
There is no similar control of predators in the Fraser River, so they might turn out to have a greater impact there, he said.
Schreck said the findings do hint that fish-friendly improvements at the Columbia dams might have boosted salmon survival. But he said it will take more time to draw firm conclusions.
The new study was funded in part by the U.S. Army Corps of Engineers, which operates dams on the Snake and Columbia, and the Bonneville Power Administration, which distributes energy from the dams. Funding also came from private foundations and the worldwide Census of Marine Life.
It was among the first studies to make broad use of new underwater listening posts in the rivers and along the West Coast to track the travels of young salmon carrying acoustic tracking devices. The devices emit "pings" picked up by the monitoring network.
The system allowed scientists to track fish almost daily, watching how long they survived and how fast they moved.
About 50 percent of spring chinook that started from an Idaho hatchery on the Snake River made it all the way to Bonneville Dam, Welch said.
The fish traveled roughly 12 miles a day, taking about three weeks from Idaho to Bonneville Dam and four more days from Bonneville to the ocean. Many disappeared within the last stretch of the Columbia near its mouth, which is also where large colonies of seabirds feast on young salmon.
On the Fraser River, about 25 percent to 50 percent of fish made it down the river to its mouth -- a shorter distance than what the Columbia fish traveled, Welch said.
Another scientist not involved in the research said conditions on the Columbia and Fraser vary widely from year to year and the Fraser is affected by a major die-off of British Columbia forests infested by bark beetles. That makes it difficult to compare the two rivers directly, said Howard Schaller of the U.S. Fish and Wildlife Service's Columbia River Program Office in Vancouver.
"It's hard to take the information they generated and draw these conclusions from it," he said.
Many scientists who work on Columbia salmon say the fish are subject to "delayed mortality," dying in a weakened state from the stress of passing through dams. That might not have been captured by the new study, Schreck said.
"We really do believe there's a delayed mortality, and there's no question there is mortality in the dams," he said. "The dams may have less impact now, but still a significant impact on reduced stocks that are already precarious."
Biodiversity: Unraveling the Mysteries of Salmon Migration by Stephen Leahy, Science Daily, 10/31/8
Do Dams Make A Difference? IPS News, 10/30/8
Salmon Study Yields Surprise Result by Jeff Barnard, Capital Press, 10/30/8
Readers Discuss POST article by Reader Discussion, The Oregonian, 10/29/8
Salmon: No Dam Difference? by Editorial Board, The Oregonian, 10/29/8
Track the Salmon in California by Editorial Board, Contra Costa Times, 10/29/8
New Study Finds Fish Do as Well on Dammed Rivers by Editorial Board, Walla Walla Union-Bulletin, 10/29/8
Dams Appear to Have No Impact on Salmon by Michael Reilly, Discovery News, 10/29/8
Salmon Smolt Survival Similar in Columbia and Fraser by Mark Floyd, Eureka Alert, 10/27/8
Salmon Study Under Fire for Minimizing Effect of Dams by Warren Cornwall, Seattle Times, 10/27/8
Research Hints Dam Improvements Helping Salmon by Michael Milstein, The Oregonian, 10/27/8
Dams Not Main Cause of Salmon Collapse, Study Says by James Owen, National Geographic News, 10/27/8
Study Shows More Salmon Survive West's Dammed Rivers Canadian Press, 10/27/8
Radio Tags Shed Light on Salmon Migration Routes by Mark Hume, Globe and Mail, 10/27/8
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