Dams Appear to Have No Impact on Salmon

Oct. 29, 2008 -- Young salmon in the Columbia River appear to be unaffected by dams, according to new research.

The heavily dammed Columbia and its largest tributary the Snake River in the northwestern United States serve as a breeding ground to millions of salmon, including endangered chinook and steelhead species, which have been dwindling steadily for years.

Whether or not the eight dams along the rivers contribute to the decline has been a source of bitter controversy for decades. Conservation groups, the commercial and sport fishing industries and local Native American tribes have long blamed the fishes' plight on the dams. Government agencies have responded by sinking some $600 million into the watershed for research, and building structures like fish ladders that reduce the dams' impact on fish.

Now a new study published yesterday in the journal PloS Biology suggests the measures are working.

David Welch of Kintama Research in Canada, a company that develops equipment for tracking marine life, and colleagues tagged 1,000 young chinook and steelhead salmon in the Columbia-Snake rivers and the undammed Fraser River in British Columbia. They tracked the fish as they navigated out to sea through the rivers, and then compared survival rates in the two rivers.

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In the Columbia they found the fish survived just as well, if not better than fish swimming down the Fraser River even though they have to swim 600 kilometers (373 miles) further. To account for the difference the researchers measured fish survival per 100 kilometers (62 miles) of swimming.

By that metric 80 percent of young fish survived per 100 kilometers, versus 60 percent in the Fraser.

"I was bowled over," Welch said. "Everybody including me thought we'd see much lower survival in the Columbia."

However, Welch said the results don't mean dams are good for fish. They may have a long-term impact on survival that the researchers didn't see.