State may have found Mussel evidence in Flathead Lake

by Dennis Bragg – KPAX (Missoula)

They’re still running tests, but biologists are worried they may have found evidence of exotic mussels making an appearance in the waters of Flathead Lake.

Montana Fish, Wildlife and Parks says microscopic larvae have shown up in four of 17 plankton samples that were taken from a sample collected in July near Woods Bay on the north end of the lake.

Eileen Ryce, FWP’s aquatic invasive species coordinator, says samples were sent to three out-of-state laboratories for testing last week.

Test results from independent labs in the Midwest suggest that tiny organisms within the sample have characteristics consistent with zebra and quagga mussels. Results from a lab in Oregon, however, suggest the sample shows no sign of mussel contamination.

“These larvae are notoriously difficult to identify at this stage of development,” Ryce explained. “With this sample the question mark is the size of the larvae, which are significantly smaller than what we’d expect. But we’ll err on the side of caution.”

Ryce said FWP will send a team of divers to several locations on the north end of Flathead Lake to search for adult mussels, which could be as tiny as sesame seeds.

The sample that contained the suspicious, microscopic larvae was among 11 collected from Flathead Lake by volunteers from the Whitefish Lake Institute in July and delivered to FWP in late September. The remaining suspected samples will be submitted for additional DNA testing.

FWP has also alerted downstream agencies in Idaho, Washington and Oregon since the organisms could be carried into the extensive Columbia River system via the Flathead River.

Zebra mussels were first discovered in the Great Lakes in the 1980s and appeared in Lake Mead in 2007, causing all Western States to begin screening for their spread. In Montana testing has focused on Flathead, Fort Peck Lake and Canyon Ferry because those waterways see the highest amount of non-resident boating traffic.