Signs of invasive exotic mussels have been found in Flathead Lake.
Although verification testing is still under way, Montana Fish, Wildlife and Parks Department officials say they are taking seriously the warning signs detected in a routine plankton sample taken in July from the northern end of Flathead Lake, which eventually feeds Lake Pend Oreille.
Test results from independent labs in the Midwest suggest that tiny organisms within the sample have characteristics consistent with zebra and quagga mussels, Montana officials said.
However, results from a lab in Oregon suggest the sample shows no sign of mussel contamination.
“These larvae are notoriously difficult to identify at this stage of development,” said Eileen Ryce, aquatic invasive species coordinator for Montana Fish, Wildlife and Parks.
Idaho, Washington and Oregon officials were notified on Friday, she said. Neither zebra nor quagga mussels have been found in Montana or Idaho.
Discovered in the U.S. in Great Lakes in the 1980s, zebra mussels have since spread throughout most major rivers in the Midwestern and mid-Atlantic states. The exotic mussels do not have a predator in North America to keep numbers in check, so they can reproduce and spread rapidly, especially on hard surfaces like marina docks and piers and on boat motors and hulls.
“We’re remaining cautiously optimistic that it won’t pan out to be invasive species,” said Chip Corsi, Idaho Fish and Game Department regional manager in Coeur d’Alene. “Although we could just as easily be pessimistic at this time. One thing for sure, nobody wants them.”