Aquatic weed more prevalent in Jefferson than previously thought

A recent aquatic noxious weed survey on the Jefferson River confirmed what officials has suspected, that Eurasion Watermilfoil has a firm foothold in the waterway.

“We knew it was there last year, we just didn’t know how far up it was,” said Celestine Duncan, a noxious weed coordinator with the Montana Department of Natural Resource and Conservation. “We new it was at least 15 and a half miles up stream (of the Missouri Headwaters), but this survey puts it a little higher.”

Researchers recently canvassed the Jefferson River from where it begins at the confluence of the Beaverhead and Big Hole Rivers near Twin Bridges down to where it meets with the Madison and Gallatin Rivers to form the Missouri River.

The furthest upstream they fond Eurasian Watermilfoil was at the mouth of the Boulder River just downstream of Cardwell, Duncan said.

Eurasian Watermilfoil is an aquatic invasive weed that is native to Europe. It is found in a few places around Montana, including Noxon Reservoir on the Clark Fork River and in Toston Reservoir on the Missouri River north of Three Forks.

The weeds spread naturally by fragmenting and dispersing downstream, Duncan said. Humans can spread it by moving pieces of the plant from one water body to another either on boats or other equipment.

Another way to spread the weed is by dumping fish aquariums in natural water bodies, she said.

Eurasian Watermilfoil used to be commonly sold as an aquarium plant and sometimes when people dumped their aquariums in a pond, ditch or stream the plant took root, Duncan said.

Surveyors will be looking this week for the weed in the Boulder River and some backwaters near Whitehall, trying to pinpoint its locations, she said.

The news that Eurasian Watermilfoil has made its way to Madison County is troublesome, said Madison County Commissioner Dave Schulz.

The county has been vigilant for years on land-based noxious weeds, like knapweed. But an aquatic invasive weed is a different challenge, Schulz said.

“Unfortunately, it’s a totally different animal because it’s an aquatic thing and because the Jefferson River is a moving waterway it’s going to be incredibly difficult and challenging to manage,” he said.

In a river environment, the moving water makes controlling an outbreak of Eurasian Watermilfoil quite a challenge, Duncan said. The main control method will be hand pulling, which is difficult and expensive.

In calm water, like a lake or reservoir, dredges and hand pulling are preferred options, she said.

The main concern with having the weed present in the Jefferson River isn’t the impact the weed will have on the river itself, but that it gives it a foothold to spread to other rivers and lakes, Duncan said.

“The big risk to me is that it’s one more area for people who are moving boats to move it from one place to another,” she said.

Many lakes in the area would be prime spots for Eurasian Watermilfoil to flourish and so people must be vigilant to remember to clean, dry and inspect their boats and fishing equipment, Duncan said.

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