Dam Removal Not Salmon Solution, Researchers Sayby United Press International
November 2, 2000
WASHINGTON, Nov. 2 --Reviving the west coast salmon stocks will take more than just tearing down dams, U.S. government researchers say. At least some conservationists, however, maintain that the dams are still the problem.
The number of spring and summer chinook salmon in the Columbia River System have been declining for years, according to zoologist Peter Kareiva of The National Marine Fisheries Service. Dam construction throughout the river system has almost certainly played a part in the decline, he noted.
But a computer model of the fish population shows, said Kareiva, that even if the dams were removed -- so that all returning salmon made it upriver To spawn and all the young made it back down to the mouth of the Columbia the stocks would continue to fall.
But "modest" improvements in survival of the salmon during the first year or once they reach the ocean could reverse the decline, said Kareiva in Thursday's edition of the journal Science.
"Management aimed solely at in-river migration survival cannot reverse ...the decline," he emphasized.
Conservation scientist Scott Bosse of the advocacy group Idaho Rivers United disagreed.
The science of the paper is flawed, said Bosse. "The chief assumption of The paper is that the hydro system has been fixed," he said. "That's an unfounded assumption that's not supported by on-the-ground research."
Bosse, whose group was among the first to advocate removing several of The power dams in the Columbia River system, said the issue has become a major issue in the presidential campaign in the Pacific Northwest.
Kareiva said that harvest rates in the river had been reduced to about 10 per cent. This, plus engineering improvements, means that about 60 per cent of young fish survive the migration down stream. In addition about 70 percent of juvenile fish are physically moved from the top of the river to below the Bonneville Dam, the last dam on the Columbia.
Without those changes, Kareiva said, the salmon population would now be declining about 50 per cent a year instead of about 5 per cent.
"A lot of management actions -- very expensive and very controversial -- worked to some extent," he said. "But the salmon are still declining -- not as rapidly as they would have been -- but they're still declining."
Kareiva said conservation can focus on improving survival when the Salmon are very young and still living in fresh water near the spawning grounds And while they live in the river estuary before returning to the ocean.
"Even if you had 100 per cent survival in migrations," he said, "they'd still be declining and therefore you have to look at either the fresh-water stage or the estuary stage."
The computer model, Kareiva explained, shows that reducing mortality by 11 per cent in the fresh-water stage or by 9 per cent in the estuary would reverse the decline.
"So our main point is that we can't look only in the river," Kareiva said.
But Bosse said the spawning grounds and the rivers where the young fish spend their first year of life are in the best shape they've been for decades. "The salmon in the first year are just fine," he said.
"All the on-the-ground research -- with empirical evidence -- shows no decrease in first-year survival," Bosse added.
Kareiva said one way to improve survival in the fresh-water stage would be to increase available nutrients for the young salmon, perhaps by seeding the heads of the rivers with salmon carcasses, which are a main source of food for the young fish. "The faster you grow, the lower your mortality is," he said.
In the mouth of the river, Kareiva added, the salmon face two main threats -- predators, including man, and competition from hatchery-raised salmon. Competition could be reduced, he said, by releasing hatchery fish on different schedules, so that they don't compete for food with the wild salmon.
Kareiva did note that the dams on the river could still be having an effect.
"There is a hypothesis that (the salmon are) so stressed by having run the gauntlet that they're weakened and they go out to the ocean and die," Kareiva said.
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