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Fish slides add new wrinkle to salmon debate

7/31/2006

POMEROY, Wash. — An engineering wonder that gives young salmon an easier, safer route through dams without reducing hydropower generation has shifted the debate over endangered salmon.

The removable spillway weir, or fish slide, tested for four years at Lower Granite Dam, is a prototype that federal fisheries and dam managers hope offers an alternative to removing some dams to save salmon, a symbol of the wild heritage of the region.

The slide allows the fish to migrate through the dam when they're ready, sliding through the spillway like children at a water park.

"The fish slides are the largest improvement in these dams since adult fish ladders were developed," said Robert Lon, Pacific Northwest director of the National Marine Fisheries Service. "They represent the best opportunity for fish passage so long as the dams are in place."

Since the 1980s, a debate has raged over the fate of declining populations of salmon and steeled in the Columbia and Snake rivers. Much of that debate has centered on the effects of eight Snake and Columbia River hydroelectric dams, and the best way to get migrating salmon past the dams.

Federal officials changed the debate by creating the fish slides they hope will allow salmon to survive their downstream journey in the river and require less water to be "spilled" over the dams and lost to power generation.

These officials contend the fish slides give them enough improvement in migration that they don't have to breach dams.

But state and tribal scientists and salmon advocates remain skeptical that the fish slides can improve river conditions enough to restore viable populations of salmon to Idaho's largely intact spawning habitat in the Salmon River and its tributaries. Even though 12 stocks of salmon are listed as endangered or threatened, Idaho's salmon are the stocks affected primarily by the Snake dams.

Here's why scientists say it comes down to the dams:

Idaho's salmon return at a rate three to four times lower than salmon that go through only three to four dams.

Much of central Idaho's spawning habitat remains pristine, like the Middle Fork of the Salmon, so habitat restoration won't help.

These fish have never been mixed with hatchery fish so they suffer no genetic weaknesses.

Few of these wild fish are harvested.

That leaves dam passage or losses in the Columbia River's estuary as the only man-made limitations on fish survival.

The returns for these Middle Fork spring-summer chinook would have to double to reach the scientists' current estimate on how many, on average, of these fish must spawn to survive, National Marine fisheries officials said.

This "gap" presents the greatest challenge for federal dam managers and fisheries officials to develop plans for operating dams that meet the Endangered Species Act.

Federal dam managers and Lohn hope that two things will happen to bridge the gap over the next decade: the installation of the fish slides at all eight dams and new management techniques that emerge from a growing understanding of what happens to salmon when they near the Pacific.

Slides are now in place at three of the eight dams. The remaining five dams are now slated to get the weirs over the next 10 years.

But even within federal scientific ranks, there are disagreements about how effective the weirs can be.

National Marine Fisheries Service scientist Steve Smith told the Northwest Power Planning Council earlier this month that he expects only minor improvement in salmon survival, since the existing barging and fish passage facilities already provide high survival through dams.

Federal scientists still say salmon survive better in the barges when the river temperatures are too high for the fish to survive or flows are too low to flush them to the Pacific before they make the change from freshwater to saltwater fish.

And because of lack of food and increased predators in 2004 and 2005, salmon returns throughout the Northwest are expected to drop significantly the next two years.

That's why sporting groups and environmentalists remain skeptical about both the barges and the weirs and support breaching instead the four Snake dams in Washington.

"The techno-fix just perpetuates denial of the real issues," said Glen Spain, director of the Pacific Coast Federation of Fishermen's Associations. "I'd be overjoyed if the things worked, but I won't hold my breath."

Salmon do not so much swim downstream toward the ocean, as they are swept down in the current, staying within 10 feet of the surface. Spilling salmon through the spillways actually sucks the smolts — young 5-inch-long salmon that are in the process of changing from freshwater to saltwater fish — as deep as 50 feet below the surface and subjects them to unnaturally high pressures.

Some are killed outright. Others are damaged or stressed so much that they die later, or become highly susceptible to predators such as pikeminnows or walleyes. And some of the effects are not clearly understood.

The fish slide allows the salmon to ease down the spillway without the stress.

But the real benefit of the fish slide is it uses five times less water to move the fish through the dam than normal "spill," which is the term dam managers use for water that is run over the dam for fish migration rather than through the turbines to generate power. The saved water can be used to turn turbines and create electricity.

Jacobs Civil Inc., an engineering company, designed the first 1,200-ton weir that was barged from Vancouver, Wash., where it was built in Lower Granite in 2002 for initial tests. It cost $12 million. Additional fish slides were installed in 2005 at Ice Harbor on the Snake near Pasco, Wash., and in 2004 at Bonneville Dam on the Columbia near Portland.

The debate over Columbia Basin salmon and dams has raged more than 16 years in the scientific community, in political circles and the federal courts.

It is no nearer a resolution today than when Snake River sockeye salmon were first listed in 1991. Today, 12 stocks of Columbia Basin salmon or steelhead are listed as endangered or threatened.

Last year, a federal judge ordered for the fifth time since 1991 that federal dam operators and fisheries officials rewrite their plan for ensuring that the eight dams that stand between Idaho and the Pacific don't send salmon into extinction.