A boat is inspected at an Idaho boat inspection station for invasive mussels.

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Idaho boat inspection stations caught a record number of watercraft fouled with invasive mussels so far in 2021, but state officials report that its waters remain free of the aquatic invaders.

Although inspections can still take place through December, most boaters are now winterizing and putting boats into storage.

Nic Zurfluh, of the invasive species office of Idaho State Department of Agriculture, said 2021 was not quite as busy as 2020, but more zebra or quagga mussel-fouled boats were discovered at inspection stations coming into the state this year.

“We had a big year as far as quagga and zebra mussel-fouled boats,” Zurfluh said. “We’re currently at 52.”

The Malad inspection station for eastern Idaho, operated by the Onieda Soil and Water Conservation District, nabbed the lion’s share, catching 25 mussel-fouled boats in 2021. Idaho reported 35 mussel-fouled boats in 2020, 48 in 2019, and 50 in 2018. Inspection stations logged about 115,000 boats in 2021 and 130,000 in 2020. The state has more than a dozen inspection stations, most on key highways crossing the border.

Inspection records show that most of the mussel-fouled boats passing through Malad had been playing in the infested water at Lake Powell in Utah.

Zurfluh speculated that the jump in mussel-fouled boats over last year was related to the pandemic.


A boat rope is shown infested with invasive mussels at an Idaho boat check station.

“Watercraft inspections showed that boaters last year traveled very locally within Idaho, and maybe Idaho and Utah or Idaho and Washington,” he said. “This year, even though we saw fewer boats, I anticipate longer distance traveled. Maybe last year they didn’t take their trip to Lake Powell, but this year with some of the COVID restrictions being lifted, folks are taking those trips.”

Zurfluh said boats coming from other states or waters known to have mussel-infected water are given a closer inspection and routinely given a free, hot water power wash. State inspectors also visit all state boating waters to take samples and visually inspect for signs of invasive mussels. So far, the procedures seem to be keeping the invasive mussels out of Idaho.

“Every year — knock on wood — we’ve been doing this monitoring for about 12 years and we haven’t seen any signs of quagga or zebra mussels,” Zurfluh said. “That really speaks to this whole idea of prevention being alive and well in Idaho. It’s a lot more cost effective overall to prevent mussels from coming in, rather than dealing with the mitigation and removal costs on the back end.”

An Idaho-specific analysis showed that the small invasive mussels, if introduced in the state, would have a $94 million annual impact on the state, not including the agricultural impact, the Idaho Press reported in 2019.

Zurfluh said the total number of mussel-fouled boats could still climb higher for the year even though inspection stations are closing because boat owners can still request a free inspection and hot water power wash.

Boat owners can request an inspection at

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