BY SUSAN PALMER
The Register-Guard (Used with permission)
Friday, Aug. 20, 2010
BLUE RIVER — The U.S. Army Corps of Engineers spent $10 million this year on a complex system to move spring chinook salmon from the base of the Cougar Dam to the South Fork McKenzie River above the dam.
It was the third run at a vexing problem with no guarantee that it would work.
Corps fish biologist Greg Taylor could be forgiven for worrying whether chinook — declared endangered under federal law in 1999 — would venture into the concrete and steel waterway system once it was operational this summer.
Spring chinook — the largest of the salmon species, weighing between 40 and 120 pounds — once coursed up the pre-dam McKenzie River and the 25 miles of the cool clear South Fork, some of the most productive fish habitat in the basin.
Cougar Dam, 456 feet tall and built in 1963, changed all that, blocking the fish from moving upstream. At the time, Corps engineers gave consideration to the fish, building a facility at the base of the dam that would allow officials to trap salmon and haul them by truck past the reservoir and to the river.
But once the dam was in place, salmon stopped dead at the mouth of the South Fork, about 4½ miles downstream of the dam. They came nowhere near the trap, put off by the cold water being spilled into the river from the deepest part of the dam.
The Corps built a fish hatchery to mitigate for the loss of habitat, but that didn’t keep the salmon numbers from continuing to decline.
By 2005, the Corps had built a $55 million temperature control tower on Cougar, allowing the agency to pull warmer water from the reservoir into the river, a move that did attract fish to the base of the dam.
But the old trap and haul set-up was old and inadequate.
Building the new system during the past year employed about 30 people per month during its busiest season, with $3.5 million in contracts with local subcontractors and $2.5 million with area suppliers.
The resulting Cougar Dam Adult Fish Collection Facility is a lengthy concrete fish ladder that starts at the base of the dam and stair-steps up through 31 small pools to a holding tank where a worker can sort the wild salmon from the hatchery-raised fish — identified by their clipped adipose fin.
A burst of water into the holding tank encourages the fish to leap into a narrow water-filled raceway where they can be directed via a moving gate either into another tank that empties into a truck below or into a smaller tank where they can be briefly anesthetized and a small DNA sample taken. The Corps plans to sample all the fish, Taylor said.
Knowing their lineage — whether they are the offspring of wild or hatchery fish — will allow the Corps to track which fish are most successful in South McKenzie, he said.
It matters because recent studies of steelhead have shown that the offspring of wild fish are much more robust than those of hatchery fish or even of wild/hatchery crosses, said Oregon State Fish and Wildlife biologist Jeff Ziller.
Biologists want to know if the same is true for salmon, he said.
The Cougar system is unique, Taylor said, borrowing ideas from projects throughout the Pacific Northwest.
Rather than pushing or crowding fish, the guiding principle was to let them make their own way from the river, up the ladder and to the truck tank with as little impediment as possible.
To make it happen, two big pumps pull water out of the river and send it pulsing through the artificial waterway. The high flow attracts salmon, Taylor said.
“We wanted the fish to do as much on their own as possible. Any time you handle a fish, you stress the fish,” he said.
On July 27, workers sent water spilling down the ladder for the first time.
Then they waited.
In an hour, a lone salmon had swum up the ladder to the first holding tank. Within four hours, 40 more had followed.
“I was so gratified,” Taylor said. “Your heart’s in your throat because you just don’t know.”
Since then, the truck — which can hold about 60 fish — makes a couple of runs a week, carrying salmon up to the river, Taylor said.
Salmon aren’t the only fish benefiting. The system also attracts bull trout — another endangered species that needs the run of the entire river.
Both bull and rainbow trout have made their way up the fish ladder and into the tanks; that’s a good sign, Taylor said.
The goal is to get at least 1,000 Chinook salmon into the river’s upper reaches.
But it’s far shy of the historic fish runs. Long before dams were built, as many as 200,000 spring chinook made their way up the Willamette, with between 50,000 and 80,000 heading up the McKenzie River, Ziller said. The South Fork had excellent spawning and rearing habitats and may have attracted 25 percent of the McKenzie River chinook, he said.
The temperature control tower and the trap and haul facility will help bring the adult salmon back, but there’s still more to do.
Juvenile fish heading downstream must make their way through the dam’s hydroelectric turbines or a narrow waterfall functioning as a regulating outlet for the dam. Either route kills a percentage of the fish, Taylor said.
The downstream improvements are still on the drawing board, but a clock is ticking.
Under a lawsuit filed by Willamette Riverkeeper against the National Marine Fisheries Service and settled in 2008, the government must complete downstream fish passage at Cougar by 2014.
Travis Williams, executive director of Willamette Riverkeeper, is hopeful about the latest development.
“It doesn’t represent the ideal for these fish, but it should increase the numbers that ultimately are able to pass above the project,” he said.