Aquatic invasive species creeps into Flathead Lake

A reported sighting of Eurasian watermilfoil in Eagle Bend Yacht Harbor waters led to the discovery of large quantities of curleyleaf pondweed in the harbor and waterways that surround it.

A survey funded through Lake County, the Flathead Lakers and the Department of Natural Resources and Conservation, and led by Eric Hanson of the Flathead Aquatic Invasive Species group found no traces of watermilfoil.

But, Hanson said the survey results showed a different aquatic invasive species, curleyleaf pondweed, has heavily infested (40 percent of the plants) the Eagle Bend harbor and channel. It was also found in patches along the Flathead River bottom leading upstream for a couple of miles, in Fennon Slough and in two places in Flathead Lake—just outside of the harbor in Somers and along a seawall outside of Bigfork.

“We’re guessing that it’s been in the yacht harbor between five and seven years,” Hanson said.

Now that the invasive species is found, the discussion in Flathead County is how to deal with the problem. The outcome will be determined by where the money comes from and what partnerships are formed between government agencies, non-profit groups and private landowners.

“Right now the infestation is really small. We’re at a point where it’s cost-effective and we can eradicate it,” Hanson said.

The Invasion

He thinks the process would take two to three years and cost around $50,000. If the combative process doesn’t start this year, then the funding and time needed to get rid of the pondweed could increase exponentially.

A Eurasion watermilfoil eradication project in Noxon and Cabinet Gorge is trying to catch up with 400 acres of the invasive plant. Hanson said the cost is approaching $1 million and the watermilfoil isn’t controlled yet.

In a couple of years, curleyleaf pondweed could spread to as much as 100 acres of Flathead’s waterways. Hanson said that would not be good for fish or other aquatic plants and animals.

“Instead of having a diverse aquatic community,” He said. “You get a mono-culture of really thick curleyleaf pondweed and nothing else will grow in it, and it kind of deprives the fish of their habitat.”

A boat launched in the Eagle Bend harbor is the most likely culprit for introducing the plant into Flathead waters. Pondweed has made it’s way into every state except Main, South Carolina, Alaska and Hawaii.

The aquatic weed consists of a thin stem with blue-green leaves attached in an alternating pattern. Turions, a hard pinecone-like bud that falls off the plant, form in the spring. They are carried by water currents to new locations. Wherever they land, they can start a new plant. Turions’ germination rate is 60-80 percent.

Combat strategies

The fight against pondweed can take a few different routes. Caryn Miske of the Flathead Basin Commission said herbicide, barriers and dredging are some of the options being discussed.

The harbor, channel, river and lake will all be attacked differently.

Since the harbor and channel are so heavily infested mechanical dredging and/or application of an herbicide targeting curleyleaf pondweed are the only options.

Herbicide is best applied when the water levels are low. Not only to keep the herbicide out of the lake, but also to keep the chemicals from becoming diluted. Miske said while the herbicide can target curleyleaf pondweed specifically, there can still be some residual effects among other aquatic plants.

Mechanical dredging essentially scrapes the all the dirt and muck off the bottom so it can be sucked up to the surface with a vacuum.

“Dredging is going to pull out both good and bad, but you can direct them,” Miske said.

The channel is a better candidate for dredging than herbicide because of it’s proximity to the lake. But, another option for the channel is to put a barrier across the entrance to the lake and then put herbicide in the channel.

In the lake, river and slough curleyleaf patches are spread out and not as thick. Therefore hand dredging or laying down mats to smother the plants are viable options. Hand dredging involves divers that would hand pick the plants for the vacuum to suck to the surface. Mats would prevent sunlight from reaching the plants and prevent turions from spreading.

But before any plans can move forward an agreement has to be reached between the interested parties. Miske said the basin commission has worked to organize meetings between parties with vested interests.

Parties like the Eagle Bend Yacht Harbor Boat-slip Owners Association, the county weed district, DNRC, the Flathead Lakers, individual landowners, Fish, Wildlife and Parks, the Department of Agriculture, the Department of Environmental Quality and Flathead AIS.

At this point Eagle Bend has agreed to contribute $10,000 to the effort, but only if other parties step up to the plate to put money in the pot and a larger plan to combat aquatic invasive species can be agreed upon.

Who else will contribute money and a plan of action still need to be determined.

The next few meetings will determine how to proceed this summer.

“At this point we’re waiting for the weed district to implement a plan,” Miske said.

Weed district

Head of the county weed district, parks and recreation, and building maintenance Jed Fisher said it’s not so easy to just come up with a plan and implement it. Flathead County’s first introduction to aquatic invasive species management came last year with the discovery of Eurasion watermilfoil in Beaver Lake.

It cost the county about $5,000 to start that management project, but it was money that was not allocated for aquatic species management.

Fisher said the county is just starting to educate itself on the best ways to manage aquatic invasive species and asking for money to do so, because the weed district budget is already allocated toward things like noxious weed management.

“I do not have any money dedicated to aquatic weed control,” Fisher said. “This issue is fairly new.”

The county weed department has applied for three grants that would amount to funding up to $60,000 if approved.

Flathead’s weed district also needs to work with water and land controlling agencies on gaining access to affected areas and the best ways to go about combating the invasive species. The DNRC, private landowners, FWP, and the Department of State Lands all have a say in the matter.

“I have to be in partnership with these partners,” Fisher said.

Fisher not only wants a plan to take care of the current curleyleaf pondweed infestation, he wants to survey as much of the water in Flathead County as he can. Then he can come up with a plan and allocate money toward control of aquatic invasive species in the county as a whole.

He is currently in the process of applying to the DNRC for two state surveyors to help two weed district employees in surveying Flathead County lakes for aquatic invasive species this summer.

As far as pondweed is concerned Fisher expects some work will be done this summer to begin testing the best way to combat the plant. At a minimum the weed district wants to allocate $5,000 toward doing some test plots that determine the effectiveness of an herbicide and begin some mechanical and hand dredging.

For now, the next step is another meeting between all the partners.

“This is a new ball game for me and I want to do it right,” Fisher said. “I’m really easing into this.”