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What’s at stake as Idaho evaluates its mussel eradication efforts

What’s at stake as Idaho evaluates its mussel eradication efforts

Michael Stephenson has been worried for years about a tiny invasive creature smaller than a fingernail. Then, last fall, they came. Quagga mussel larvae and an adult specimen were found in the Snake River near Twin Falls.

“I’m very concerned about this,” said Stephenson, a biologist with Idaho Power, which operates 17 hydroelectric dams on the Snake River and its tributaries, 15 of which are below where the quagga mussels were discovered.

Stephenson said the tiny mussels are a big problem. They spread quickly – a female can produce a million eggs a year – and they attach themselves to virtually any surface in the water. They can clog inlets for drinking and irrigation systems, as well as water turbines.

The Columbia River Basin is the only major river system in the country not affected by an invasive mussel infestation. The Pacific Northwest Economic Region estimates that controlling the problem would cost the Northwest $500 million a year.

At an Idaho Power dam near Hagerman, Stephenson points to a metal filter through which water flows from the reservoir into the power plant. This is one of the first points where quagga mussels could disrupt the system. They would start to encruste the steel rods, Stephenson said, thereby reducing the amount of water entering the dam.

The company currently uses a mechanical rake to keep branches and plants out, but divers may be needed to remove quagga mussels. The mussels may also target other pipes that bring water to cool the system while the turbines are running; without the cold water, they could overheat.

After visiting the Southwest to see how the Hoover Dam operators are dealing with quagga mussels in Lake Mead, Idaho Power is considering purchasing special ultraviolet lamps to kill baby mussels swimming by its facilities.

“If there is an infestation in the Snake River, it could be the biggest problem we’ve ever faced in terms of infrastructure,” Stephenson said.

Michael Stephenson, a biologist at Idaho Power, is studying how quagga mussels in the Snake River could affect hydroelectric plant operations and how the company can prepare.

Rachel Cohen

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Boise State Public Radio

Michael Stephenson, a biologist at Idaho Power, is studying how quagga mussels in the Snake River could affect hydroelectric plant operations and how the company can prepare.

Last fall, Idaho dumped a copper-containing chemical into the river in an attempt to eradicate the mussels. Similar poisons have successfully killed mussels elsewhere, but this treatment in a major river was unprecedented.

“This is something I’m very concerned about,” said Nic Zurfluh, director of the Idaho Department of Agriculture’s invasive species office. “I just wanted to gauge how effective the treatment was last fall.”

Zurfluh said it’s been a long winter of waiting to see if the mussels have disappeared. They stop breeding in the colder months, so they’re not as easy to spot then. As temperatures rise, Zurfluh’s team will begin collecting water samples across the state, focusing on the Snake River near Twin Falls, to look for signs of mussels.

Quagga mussels infest an Idaho license plate.

Senator Michelle Stennett

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Jeremy J. Gugino

Quagga mussels infest an Idaho license plate.

Thanks to funding from Parliament, these efforts will be doubled this summer, but Zurfluh warns that it may take some time to get answers.

“I think that the lack of discoveries would be really great news,” he said. “But just knowing that won’t give us the complete picture until we haven’t made any discoveries for quite some time.”

The tiny mussels are difficult to find and it can take several months or even years before the all-clear is given.



If the mussels are still there and drifting downstream, they could pose a major threat to anadromous fish that migrate from their inland spawning grounds to the ocean, bringing with them vital nutrients – nutrients that the quagga mussels absorb. The mussels are excellent filter feeders, says Anthony Capetillo, an invasive species biologist with the Nez Perce Tribe and a tribal member.

“When the quagga mussels suck all the oxygen and nutrients out of the water, the fish are deprived of the nutrients and cannot grow as normal,” Capetillo said.

Salmon in particular, he says, are already suffering from the dams and climate change, and the quagga mussels, whose sharp shells cover the fish ladders, could make their migrations even more dangerous.

“All the money we’ve put into all these projects to get these salmon, steelhead trout and lamprey back into these waters,” Capetillo said. “All of that could potentially have been for nothing if we allow these invasive species to come in and spread.”

There is a lot at stake, he said, for a region where clean water and access to nature are highly valued, but perhaps even more so for tribal communities.

“When we lose parts of our identity,” he said, “and lose our resources, we cannot really measure the magnitude of those losses.”

Even further downstream, Justin Bush, the Washington Department of Fish and Wildlife’s aquatic invasive species policy coordinator, said it could take as little as a week for floating veligers to make it from Twin Falls to the state border.

“We feel like this threat is right on our doorstep,” he said. “It’s causing us to think about a new timeline, new measures and new levels of funding that will be needed both in the short term and in the long term.”

Last fall, when the mussels were discovered in Idaho, Washington moved its surveillance teams closer to the border. But they were unable to find anything.

Now the state will have a dedicated clam monitoring team for the Snake River, fully staffed boat inspection stations in the southeast, and a new clam detection dog.

“All eyes are on Idaho and we await further information,” Bush said.

Idaho authorities hope their eradication efforts have prevented an infestation, Zurfluh said.

On the banks of Twin Falls, the state requires that all boats entering or leaving the river be washed down to prevent remaining mussels from spreading to other waters. And prevention remains key, Zurfluh said. All it takes is a single boat or kayak carrying new mussels to trigger another introduction tomorrow.

Find reporter Rachel Cohen on X @racheld_cohen

Copyright 2024 Boise State Public Radio

The ISDA hopes that the chemical treatment will eradicate the quagga mussel before a new population can form in the Snake River.

Rachel Cohen

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Boise State Public Radio

The ISDA hopes that the chemical treatment will eradicate the quagga mussel before a new population establishes itself in the Snake River.

Copyright 2024 Boise State Public Radio News