Montana Fish, Wildlife and Parks Thursday announced it detected additional evidence of invasive mussels in one eastern Montana reservoir last summer. The detection raises a few red flags.
FWP found microscopic invasive baby mussels in Tiber and Canyon Ferry Reservoirs for the first time in the fall of 2016. But the state agency and its partners didn’t find any last summer.
On Thursday, the agency announced it found bits of mussel DNA in samples taken from Tiber Reservoir last July.
"What this DNA means though is something we're going to have to investigate further," says Tom Woolf, the Aquatic Invasive Species bureau chief for FWP.
The initial discovery of baby mussels in 2016 didn’t necessarily mean that there is an established breeding population in Tiber. Each new positive detection makes that seem more likely. But environmental DNA, or eDNA, can sometimes lead to false positives.
Gordon Luikart at the University of Montana’s Flathead Lake Biological Station has been pioneering eDNA detection of invasive mussels for the past six years. He says Thursday’s announcement was disappointing, but not surprising.
"This is a weight of evidence thing," Luikart says. "The more evidence we have that they're here, the more likely that they're actually here."
FWP’s Tom Woolf says the state needs to figure out how eDNA fits into the its early detection protocols.
"What we're doing is bringing together a scientific advisory panel to help us, advise us on how we interpret and respond to information like this."
The Montana Invasive Species Council, housed in the Department of Natural Resources and Conservation, plans to put that panel together before spring.
Tiber and Canyon Ferry Reservoirs are both considered mussel-positive water bodies. The precautions put in place last year, like extensive sampling and mandatory boat inspections and decontamination, will remain in place for at least the next few years.
Learn more about the threat of invasive mussels in our 5-episode podcast, "SubSusurface: Resisting Montana's Underwater Invaders."