Flushing the fish

Fisheries manager Jim Fredericks wants to use water to kill one type of trout and help another.
A massive pulse of water from Palisades Dam, in fact.

From May 21 to May 24, the Bureau of Reclamation will open the spigot at Palisades Dam and release a third more water than normal in the South Fork of the Snake River.

Biologists such as Fredericks hope the spike in flows will scour the eggs from rainbow trout spawning areas and kick-start the breeding season for the river's native fish: Yellowstone cutthroat trout.

It is the first time in Idaho that federal water managers will use irrigation water to help one species of fish at the expense of another. Experts hope the change will help cutthroat breed more effectively while decreasing the number of rainbows produced.

If that happens, there will be less chance that eastern Idaho will be saddled with endangered species regulations.

"I think this is extremely cool stuff," said Chris Jansen Lute, the bureau's water resources manager. "Never before in my career have I seen a marriage like this between irrigation and fisheries interests."

Biologists in recent years have changed the rules to rub out rainbows, which are not native to the South Fork and coddle cutthroat. Unleashing spring flows on rainbow nests is the most aggressive move yet.

"Rainbow spawning should be disrupted by high flows," said Fredericks, fisheries manager for the Idaho Department of Fish and Game. "We also believe high flows may trigger more cutthroats to spawn in more friendly conditions."

To allow for the May surge in water, water managers cut the wintertime flow in the famed river and stored it in Palisades Reservoir. The water that will be used in the spike will be caught by American Falls Reservoir, so no irrigation water will be lost.

"We aren't talking about new water or extra water," Lute said. "We're talking about shaping releases differently to help cutthroat trout."

All this is being done with irrigators' blessings.

"My view is if we can do things that help the fish, and it's not to anybody's detriment, we are certainly willing to help," said Ron Carlson, the region's watermaster.

Biologists and Trout Unlimited officials believe cutthroat trout evolved and thrived by spawning when spring flood flows recede. But when Palisades Dam was built, spring flows were controlled and the peak of the flood was shaved off, which hurt cutthroat trout.

"Currently, the thought is that cutthroat spawn in areas where their fry can't do well," Fredericks said. "By creating the peak, we hope cutthroat will move and spawn in areas better suited for them."

The Bureau of Reclamation paid for the study into the relationship between dam releases and trout populations. And bureau officials are making the project work, said Scott Yates, a regional representative for Trout Unlimited.

"Frankly, Idaho has been lucky because of leadership we're getting on this," Yates said.