Quagga mussels are still present in the Snake River after two years of aggressive treatment.
On Friday, the Idaho Department of Agriculture reported eradication efforts in 2024 and 2025 cleared about half of the still affected waterways since last year, or 3.5 miles, but the invasive species remains present between Shoshone and Twin Falls.
Efforts to eradicate the invasive species started when juvenile mussels were first detected in the state in 2023.
Director of the Department Chanel Tewalt said without intervention, the infestation could take over irrigation and hydropower pipes, costing hundreds of millions of dollars in direct and indirect cost.
“In some cases, it's cheaper to replace the infrastructure than it is to clean out the quagga mussels,” she said.
The ISDA said no mussels have been detected in Magic Valley reservoirs so far.
In a press release from the ISDA, Alan Hansten from the Side Canal Company North called for the ISDA to continue taking “aggressive actions” against the invasive species,
“Quagga mussels could cripple the canal systems and on-farm irrigation systems that deliver water to crops across Southern Idaho, and be devastating for irrigators,” he wrote.
In August, State Fish and Game told the Idaho Statesman that 48 of 49 white sturgeon died as a result of the copper treatment used to fight the quagga mussel. The majority of invertebrates in that section of the river also died from the pesticide.
The invasive species outcompetes other food sources in the ecosystem and can permanently alter the ecosystem, which would cripple the sturgeon population.
“We would not expect a sturgeon population to survive a quagga mussel infestation in the Snake River,” said Tewalt. “So while our treatment obviously has downsides to it, they are temporary as opposed to an infestation, which is forever.”
One mollusk can lay 500,000 to one million eggs per year.
“There's this mental weight to it. We a) know what's at stake. And b) we don't have a roadmap,” Tewalt said. "We are building the plane while it's flying, and no one's ever done it before.”
In July, the Department reported no quagga mussels had been detected in the Snake River in 2025. In 2023 and 2024, they were not detected in the waterways near Twin Falls until late September.
Since they were first detected, the ISDA doubled its monitoring of the water and increased boat inspections by 50%. This year, the Department analyzed over 450 samples in the infested area.
The ISDA will try to wipe the mussels out with another ten-day copper treatment on the mid-Snake River in October. Tewalt said quagga mussels will be considered eradicated if they remain undetected in the waterways for five years in a row.
