Curlyleaf pondweed eradication underway in Flathead Lake

Efforts are currently underway to remove curlyleaf pondweed, a nonnative invasive species, from areas around Flathead Lake.

“While the Flathead Basin remains free of many of the most problematic aquatic invasive species, such as zebra and quagga mussels, a select number of aquatic invasive plants have made their way into the Flathead and pose a threat to both the economic and ecological assets in the basin,” Flathead Basin Commission executive director Caryn Miske said.

Aquatic invasive species can foul boats, degrade water quality and wreak havoc on many native species. The economic impacts are equally adverse — once aquatic invasive species become established in a watershed, property values and tourism revenues generally decline by 10 to 30 percent, Miske said.

Lake County and the Lake County Conservation District, using funding from the Montana Department of Natural Resources and Conservation and 223 grant programs, are working together to take pro-active steps to treat and potentially eradicate one of the most problematic aquatic weeds that has been colonizing Flathead Lake over the last several years — curlyleaf pondweed.

“We are at a critical juncture in terms of fighting aquatic invasive weeds,” Lake County Director of Environmental Health Susan Brueggeman said. “If our efforts at eradication are to be successful, we must act now.”

At least seven bays or channels in the northern half of Flathead Lake have small to moderate infestations of curlyleaf pondweed — Peaceful Bay, Bigfork Bay and shoreline, Caroline Point Bay, Dewey Bay, Mission View Bay, Lakeside Bay and Eagle Bend Channel. Isolated plants also have been found in about 12 miles of Flathead River channel and associated areas upstream from Flathead Lake.

“Significantly less curlyleaf pondweed now exists in Flathead Lake as compared to 2013 due to removal efforts which fully cleared curlyleaf pondweed from selected parts of the Lake, such as Dewey Bay,” Miske said, adding that the outlook for virtual eradication of curlyleaf pondweed in Flathead Lake is encouraging.

“The infestations are at a stage where they can be effectively treated using a diver dredge operation, if funding and personnel continue to be made available,” Lake County Conservation District Supervisor Jim Simpson said.

Permission forms from property owners must be obtained before diver dredge operators can enter underwater properties and remove any curlyleaf pondweed. Lake County has partnered with the Flathead Basin Commission, Flathead Lakers and Flathead Basin AIS Work Group to facilitate that job. So far, 99 percent of impacted property owners have signed on.

Aquatic invasive species surveys and curlyleaf pondweed removal will run from mid-July to early September.