Spring Runoff Kills Salmon Hatchery-Raised Fall Chinook Die Of Trauma From Nitrogen Below Ice Harbor Dam Spillway

Heavy spring runoff was blamed Tuesday for the deaths of a large number of fall chinook salmon below the Ice Harbor Dam spillway.

The hatchery-raised fish were being held in net pens to study the effects of nitrogen created by the roiling waters of dam spillways, Donna Darm, manager of the National Marine Fisheries Service Office of Environmental Policy in Seattle, said Tuesday.

“There was high mortality, as high as 85 percent” when a Fisheries Service biologist checked them Monday night, Darm said. She said she did not know the actual number of salmon that died of gas bubble trauma, a condition caused by high levels of nitrogen in water.

The Columbia River Alliance, a Portland-based coalition of river users, blamed the fish kill on a controversial NMFS program that calls for spills of more water over Northwest dams to help endangered juvenile salmon reach the ocean.

But Darm said the spill program was not in effect at Ice Harbor, where the high levels of nitrogen in the water are caused by high spring runoff, an “uncontrolled spill.”

Flows at the dam are nearly twice the capacity of its powerhouse, so roughly half the water coming into the dam is flowing over the spillways, she said.

A faulty U.S. Army Corps of Engineers gas measuring device in the dam’s raceway may also have contributed, she said.

River users cast the deaths as proof that the NMFS program to spill additional water over eight Columbia and Snake river dams is faulty.

“We have repeatedly asked our fisheries agencies to be cautious because we fear the spill program will kill the very fish we are trying to help,” CRA executive director Bruce Lovelin said in a news release. “Now it appears our worst fears have come true.”

Darm called Lovelin’s statement “a mischaracterization.”

“It’s not a situation anybody can really do anything about,” she said, noting that the agency has called for installation of “flip lips” at the base of the dam’s spillways to reduce the amount of nitrogen gas levels.

The fall chinook were “being used in an experimental way. It’s an ongoing research program set up more to see what happens to fish,” she said. “It’s important information about what effect these very high levels of gas have on fish.”