Subscribe for 33¢ / day

POLSON - Have the dreaded zebra or quagga mussels reached Flathead Lake?

"There is definitely reason for concern," Eileen Ryce, aquatic invasive species director for Montana Fish, Wildlife and Parks, said Monday.

FWP announced that microscopic larvae suspected to be from exotic mussels may be contained in four of 17 plankton samples collected from the 200-square-mile lake this summer.

Ryce hopes to send divers into Flathead's chilly waters within the next several days in search of adult mussels.

The adult mussels can be as small as a sesame seed, but put a few billion together, and they can create big problems.

The mussels - which would have arrived over land from waters infected elsewhere, hitching rides on anything from a boat hull to fishing gear - reproduce and spread rapidly. They attach to hard surfaces like rocks, docks and boat hulls, can foul boat motors, block water intake pipes, clog irrigation systems, disrupt water purification systems and impact fisheries.

The 17 plankton samples collected between May and August were sent to three out-of-state laboratories for testing last week.

Two independent labs in the Midwest reported back that tiny organisms in the samples have characteristics consistent with zebra and quagga mussels.


Results from an Oregon lab, on the other hand, showed no signs of mussel contamination.

The Midwest labs, Ryce said, told FWP that "the characteristics are consistent with mussels, but the size was smaller than you would expect."

"At the larval stage, they're notoriously difficult to identify," Ryce went on. "It's not an exact science."

But the two-out-of-three tests that say they may have arrived in Flathead, Ryce said, "have us suspicious enough that we want people to be concerned."

The evidence, Ryce said, was not enough to trigger the rapid response program of the Columbia Basin Interagency Invasive Species Response Plan team. FWP is a member of the team, which includes downstream agencies in Idaho, Washington and Oregon.

The states will remain in contact as follow-up testing continues. The rapid response program includes immediately evaluating control, containment and eradication options.

The tiny invaders have no predators to keep their populations in check.

First discovered in the Great Lakes in the 1980s, zebra mussels have spread through most major rivers in the Midwest and Mid-Atlantic states.

The first documented infestation west of the Rockies came in 2007, in Lake Mead in Nevada, with quagga mussels.

Both types are filter-feeders, and can impact a fishery's food web so much, Ryce said, that they can affect the populations of fish, "even up to the top predators."

Hence, the programs Montana and other states run imploring boaters and anglers to thoroughly clean, dry and inspect their vessels and gear any time they move from one body of water to another.

"It's the only way to prevent over-land spread," Ryce said.

The samples containing the suspicious, microscopic larvae was collected from Flathead by volunteers from the Whitefish Lake Institute in July and delivered to FWP in late September.

Remaining samples will be submitted for additional DNA testing, and divers will soon be searching Flathead for adult mussels.

But it's a huge lake, and a tiny invader.

"It's such a large system," Ryce said, "that it's really like searching for a needle in a haystack."

The problem, of course, arrives when you suddenly have billions of needles in your haystack.

Reporter Vince Devlin can be reached at 1-800-366-7186 or at


You must be logged in to react.
Click any reaction to login.