Idaho Acts Quickly After Detecting Quagga Mussel Larvae in the Snake River

The Council has worked with its regional partners over the years to prevent the spread of invasive mussels into the waters of the Columbia Basin. The basin is still the nation’s only great river system free of zebra and quagga mussels, small shellfish that attach to hard surfaces, clogging water system infrastructure and depleting nutrients from the water. The impact to an ecosystem is devastating for fish and wildlife and immensely expensive to the region’s economy.

Quagga mussel larvae were first detected in the Snake River near Twin Falls, Idaho on September 18, 2023 during routine monitoring conducted by the Idaho State Department of Agriculture, prompting officials to spring into action.

At its November meeting, Nic Zurfluh, invasive species bureau chief for the Idaho State Department of Agriculture, briefed the Council on the situation and the steps taken to prevent their spread. (See video and presentation.)

“The plan was about containment, monitoring, and treatment,” said Zurfluh. “It’s a rapid response that kicks into gear within 24 hours.”

The ten-day, comprehensive treatment plan began on October 3 and concluded on October 13, closing the river in the early days and setting up hot wash stations to decontaminate watercraft while they planned the chemical treatment. A copper-based product was applied to eradicate mussels at all life stages while still safe for humans. The treatment plan was developed with the review and assistance of many state, federal, and local entities.

“The good news is that we were able to kill the adult mussels and there was no sign of veligers (free-swimming larvae)—the treatment worked,” said Zurfluh.

“We still have a long way to go to keep monitoring for the next five years for the presence of veligers or adults. Our rapid response plan will continue to evolve and will need increased investment from the federal government and through cost-share agreements,” noted Zurfluh.

One example of regional coordination is the network of watercraft inspection and decontamination stations. In 2014, Congress passed new authorization for the U.S. Army Corps of Engineers that included a provision giving the Corps legal authority to enter into cost-sharing agreements with the four Northwest states to establish and operate these stations. The Council worked closely with regional partners to advance this legislation and support its continued funding.

The Council’s Fish and Wildlife Program recommends establishing a defensive perimeter to keep invasive mussels out of Columbia River Basin waters and identifies measures for inspection, monitoring, prevention, and the control of aquatic invasive species, including supporting regional efforts on early detection and rapid response.

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