Boise, Idaho - The Idaho State Department of Agriculture (ISDA) announced this week the detection of a small number of quagga mussels in the Twin Falls area of the Snake River.
Quagga mussels were first identified in the Twin Falls area in September 2023. Working with a broad group of partners, the ISDA rapidly implemented a treatment plan which includes extensive on-going monitoring.
ISDA Director Chanel Tewalt said, “We have a strong invasive species program in place to monitor our waterways for quagga mussels, and we are prepared to respond with a treatment plan with minimal impacts to the public. While we never want to see confirmation of quagga mussels, we know that pest eradication is rarely ‘one and done.’ Since the first detection in 2023, ISDA has conducted more water sampling, ran more inspections stations, increased statewide communications, added manpower, and worked with more partners. We have made significant progress, and now we must focus on the next phase of eradication. ISDA and the many partners who have helped in countless ways will continue to push for full eradication. We know this next phase is pivotal.”
In 2023, ISDA implemented a treatment of the river with a chelated copper product. It was the first treatment of this type and scale ever attempted in North America. Sampling results indicate the chelated copper treatment was effective in reducing the mussel population.
Since 2023, the ISDA has taken nearly 300 samples in the affected stretch of river and over 3,000 samples statewide throughout the 2024 season, doubling routine monitoring samples for the year. Current sample results show a decreased quagga mussel presence in the affected stretch of river compared to the pre-treatment survey in 2023.
Recent positive detection locations include in the Shoshone Falls pool, Pillar Falls and the Twin Falls Reservoir behind Twin Falls hydroelectric facility. Quagga mussel reproduction is more active in warmer water temperatures, making late summer the most likely time to detect the mussels in the Snake River.
ISDA is planning another strategic treatment for the affected stretch of river. Through extensive surveying this year – double the amount Idaho has ever conducted – the agency has even more information taking on the infestation this year.
ISDA does not expect major impacts to the public. Access to the Snake River at Centennial Park remains open with mandatory inspection and decontamination for all watercraft. Pillar Falls to Twin Falls Dam remains closed. An additional temporary closure from Pillar Falls to Auger Falls will take place in mid-October for approximately 15 days to facilitate a treatment. Visit idaho.gov/quagga for closure updates.
ISDA will notify the public and all involved entities once a treatment date is set and before the treatment commences.
Quagga mussels spread rapidly and clog pipes that deliver water for drinking, energy, agriculture, recreation and a variety of other uses. They also can negatively affect fish populations and wildlife habitat. If left to spread untreated, they form dense colonies that damage and hinder infrastructure so severely it would cost Idaho hundreds of millions of dollars in actual and indirect costs. This would affect every irrigator, power user and recreator.
It is essential that all Idahoans CLEAN, DRAIN, DRY all watercraft and recreational equipment. This includes boats, kayaks, paddleboards, canoes, oars, waders, boots, lifejackets, fishing gear, buckets, nets and other items.
Visit idaho.gov/quagga for the most up to date information and to sign up for e-mail updates.