Zebra mussels now found in White Bear Lake, Lake Waconia

Zebra mussels have been found in two more metro-area lakes, the Minnesota Department of Natural Resources confirmed Friday — White Bear Lake and Lake Waconia.

The mussels, a nonnative invasive species, compete with other aquatic animals for food and crowd out native mussels. They can also damage boat motors, and their sharp shells present a threat to swimmers.

In recent years, the state has ramped up efforts to eradicate the invasive mussels, which have infested nearly 200 Minnesota waterways. At Shorewood's Christmas Lake, a biological pesticide called Zequanox was used earlier this month to successfully kill mussels in a small, closed-off area.

But unlike at Christmas Lake, where the mussels found were young and isolated, the mussels at both Lake Waconia and White Bear Lake seem to be naturally reproducing, said DNR invasive species specialist Keegan Lund. At Lake Waconia, the mussels were found on opposite sides of the lake, suggesting that they reproduced and settled in, Lund said. And at White Bear Lake, an adult mussel was found in addition to juveniles.

Natural reproduction would nix the option of chemical treatment because the entirety of each lake would have to be treated, Lund said. Not only would that be expensive, but it could also cause ecological problems, he said.

"Once the population is established, the tools that you have available are really limited," he said.

According to the DNR, people should be on the lookout for zebra mussels when removing equipment like docks, boat lifts and swim rafts from the water. In the event of a suspected find, officials ask that the location be noted, a photo taken and a specimen kept for identification.