The Missouri River is under threat from invasive aquatic species, and experts say the window to stop the spread is now.
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Eurasian watermilfoil, an invasive aquatic plant native to Europe, Asia, and northern Africa, was first detected in Montana in 2007. It is now present in several of the state's waterways, including the Missouri River.
Tom Woolf, aquatic invasive species bureau chief for Montana Fish, Wildlife and Parks, says the plant spreads in a deceptively simple way.
"Eurasian watermilfoil. It's an invasive plant that's in the state. It moves just by sticking a little piece of the plant on a trailer of a boat, and that allows it to move from one place to another," Woolf said.
The plant is already well-established in parts of Montana's river system.
"We had it in places like Fort Peck. It's in the upper Missouri system. But it's not everywhere," Woolf said.
What makes Eurasian watermilfoil particularly dangerous is how difficult it is to identify. It looks nearly identical to northern watermilfoil — a beneficial native plant. The key difference is in the leaves. Eurasian watermilfoil has 12 to 21 leaflet pairs per leaf, compared to just 5 to 10 for the native species. Without knowing what to look for, most boaters would never notice it clinging to their trailer.
Once established, the plant grows fast, crowds out native vegetation, reduces biodiversity, and can form dense mats that make swimming and boating impossible in affected areas. A single plant fragment is all it takes to start an entirely new population in a previously unaffected body of water.
Mark Bell of Great Falls Boat Shop says the solution starts the moment you leave the water.
"When you get off the water, you got to make sure that all the water and kind of plant life that might be stuck to your boat or your trailer is left there in the body of water or near it, so you're not taking it somewhere else," Bell said.
The message from experts is simple: clean, drain, dry. Remove all water and plant material from your boat, trailer, and equipment before launching in a new body of water. Bell says too many people underestimate what is at stake.
"What people don't understand is the effects that these invasive species have," he said.
The threat extends beyond plants. Zebra and quagga mussels — which have already reached North Dakota, South Dakota, and Idaho — have not yet been found in Montana. But experts say the state's waterways present suitable habitat, making prevention critical. Once established, zebra and quagga mussels can devastate native fish populations, clog water infrastructure, and cause millions of dollars in damage.
To report suspected aquatic invasive species or violations of mandatory watercraft inspection requirements, contact Montana Fish, Wildlife and Parks at 406-847-6668. For more information, visit fwp.mt.gov/conservation/aquatic-invasive-species.
