Montana Fish, Wildlife and Parks to Increase Surveying Efforts After Invasive Mussel Larva Detected in Whitefish Lake

Montana Fish, Wildlife and Parks (FWP) confirmed the presence of a nonviable invasive mussel larva at Whitefish Lake, marking the first detection of invasive mussel species in the state for nearly a decade. 

The discovered larva was not yet cause for concern, FWP officials said, as monitoring has not revealed further evidence of invasive mussel species. At the Nov. 2 Whitefish City Council meeting, city officials and FWP reaffirmed their commitment to preventing the spread of invasive aquatic species (AIS) into local waters through extensive surveying and preventive measures. 

According to Tom Woolf, FWP’s aquative invasive species supervisor, a sample collected by Whitefish Lake Institute in July found a juvenile mussel on a City Beach dock. FWP was unable to determine the species, but stated that the mussel met the parameters of an invasive species. The sample, Woolf said, was dead and nonreproductive.

“With what we’ve seen, this isn’t reason for panic,” said Woolf at the Monday meeting. “It’s reason for looking closer. It doesn’t mean you have mussels out there.”

The state agency is currently working with city officials to determine next steps, Woolf said. In the meantime, FWP staff and Whitefish Lake Institute plan to increase monitoring of the lake into the fall, using microscopy and environmental DNA to determine if there are reproducing adult populations of invasive mussels. 

“Whitefish Lake is going to be on top of the priority list from here on out,” Woolf said. 

As of now, no further evidence of invasive mussel species in Whitefish Lake has been discovered following the detection of the nonviable larva. 

“This was one of our samples,” said Mike Koopal, founder and executive director of Whitefish Lake Institute. “And since the detection, Tom and his crew, if you combine what they sampled last week with what we sampled, there are now 120 samples for microscopy and 35 eDNA samples that have come back negative.”

“And we’ll be out there again this week, FWP and WLI, conducting additional sampling,” Koopal added. 

Preventing the introduction of invasive aquatic species has become an increasing area of concern in Montana. Since the introduction of its AIS Early Detection and Monitoring Program, the state has managed to stave off the likes of zebra and quagga mussels. But presence of AIS in neighboring bodies of water such as Idaho’s Snake River and the lower Missouri River in North Dakota has increased pressure to keep Montana’s waters clear. 

With no natural predators, invasive mussels can rapidly populate and outcompete native species for resources. Their presence also poses health risks to native species and humans and can disrupt recreational activities like boating, fishing, and swimming. Once introduced, FWP officials warn that AIS populations are nearly impossible to eradicate. 

In 2016, invasive mussel larvae were detected in the Tiber Reservoir with an additional suspected detection in Canyon Ferry Lake. FWP increased prevention efforts following the incidents, monitoring waters for early signs and fouling dozens of watercraft potentially carrying AIS every year. The nonviable larva in Whitefish Lake is the first detection since then. 

“I would just like to emphasize what Tom stated,” said Mayor John Muhlfeld on Monday. “Just because of the detection in July does not mean that we have exotic mussels in Whitefish Lake. Let’s hope not. But what I think this speaks to is the success of this program with early detection.” 

While increasing efforts on Whitefish Lake, Koopal urged the public to aid in early detection of AIS by checking private docks for adult, reproducing mussels. People should look for mussel and clam-like organisms the size of a thumbnail that have attached to hard surfaces and each other. Community members can report any suspected signs of AIS to the Whitefish Lake Institute by calling 406-862-4327. 

“I just want to paint some positivity out there, that the sky’s not falling,” Muhlfeld said. “We do not know if we have mussels. We’re going to figure this out.”