After nearly a decade of inhabiting Beaver Lake near Whitefish, the invasive Eurasian watermilfoil is seemingly gone — a phenomenon that many scientists call rare.

According to Montana Fish, Wildlife and Parks, no Eurasian watermilfoil was found in Beaver Lake this year following three comprehensive surveys for the first time in over a decade. Another survey will be completed in October as a follow up.

“We’re consciously optimistic that the Beaver Lake Eurasian watermilfoil can definitely be controlled,” said Mike Koopal, the executive director and founder of the Whitefish Lake Institute. “It’s definitely due to unique circumstances.”

It is rare for an invasive species to be detected and eliminated; in this case, the process took over 10 years.

Aquatic invasive species don’t have natural predators or controls to keep their populations in check. Eurasian watermilfoil, for example, will overgrow and choke off waterways, creating a monoculture of one plant.

The effort to control and eradicate the watermilfoil in Beaver Lake began in 2012 where multiple agencies worked to deploy bottom barriers, suppressing the largest population patches of the infestation. The Whitefish Lake Institute and city of Whitefish began suction dredge operations where divers remove plants as well.

In 2019, the state wildlife agency took control with the support of the Whitefish Lake Institute, utilizing more suction and divers. The institute has maintained a sediment curtain to prevent downstream drift of plant fragments into Whitefish Lake. They plan to remove the curtain this year as it has degraded over time.

WHILE BEAVER Lake is a rare success story, other invasive species continue to spread into Montana’s waters, which is why watercraft inspections are important, Koopal said.

Montana Fish, Wildlife and Parks, alongside its partners, inspected more than 86,000 watercraft this year. Of those, 45 were mussel-found and 400 were found with aquatic weeds.

“To our knowledge, we don’t have zebra mussels in Montana and so the goal, of course, is to prevent them from getting here,” Koopal said.

There are more than 17 road-side watercraft inspection stations across the state, according to the state agency. These locations can be found at https://fwp.mt.gov/conservation/aquatic-invasive-species or by calling the FWP Aquatic Invasive Species Bureau at 406-444-2440.

“Our agencies and local groups are doing everything they can to control infestations but the key is prevention,” Koopal said. “Make sure your equipment is cleaned, drained and dry before launching into a new water body.”

Reporter Kate Heston can be reached at [email protected] or 758-4459.