FISHERIES --  Commercial net-pen-raised rainbows are dying by the hundreds of thousands from the impact of the huge runoff pouring down the Columbia River through Grand Coulee Dam -- and federal water managers say there's little they can do to help the Pacific Seafood operators.

This year's spring snow melt is forcing the U.S. Bureau of Reclamation to increase water flows through the dam. The turbulent water is releasing gases, including nitrogen, which inflicts on fish a condition similar to the bends in scuba divers when they surface too quickly. Gas levels have been more than 130% of normal recently, the Seattle Times reports.

"We've easily got hundreds of thousands of dead fish," Bill Clark told the Seattle paper. He works for Pacific Aquaculture, which farms big rainbows, marketed as steelhead.

Pacific Aquaculture's parent company, Pacific Seafood, says it is losing 100,000 fish a day from the 2.7 million still living on the farm in the river 20 miles south of the Grand Coulee, according to a report on SeattlePI.com.

Washington Fish and Wildlife Department fisheries biologists say wild fish are not likely to suffer serious impacts from they increased flows, since they are not bound by nets and can move deeper to more favorable water conditions.

However, this years' big drawdown and outflow from the dam likely is flushing man rainbows and kokanee downstream and out of the Lake Roosevelt system, they say.

This year's net pen crop of sport fish in Lake Roosevelt are scheduled for release after the runoff to help assure they'll stay in the reservoir.

Pacific Aquaculture manager John Bielka doesn't agree with state fisheries biologists regarding the impacts of the flows on fisheries.

"They're basically sterilizing this entire stretch of river," Bielka told the Times. "That's going to wipe out not only the fish in our farm, but also the bull trout, the lamprey, the sturgeon and every other wild thing."

Bureau officials told the Times they have no alternative - there's simply too much melting snow that would cause flooding if the dam flow were lessened.