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Zebra mussels found in Shadow Lake

Invasive species prefers sandy areas

By Angie Landsverk

There are zebra mussels in Waupaca’s Shadow Lake.

Early last week, a city resident discovered them on the anchor of the mooring buoy for her kayak.

By the end of the week, Ted Johnson, a Wisconsin Department of Natural Resources water resource biolgoist, confirmed they were zebra mussels.

He said the specimens he examined were 3 years old.

Zebra mussels have growth rings like a tree and can generally live for three to four years, Johnson said.

Native to lakes in southern Russia, zebra mussels were first found in Wisconsin in 1990, he said.

They are one-fourth to one and-a-half inches long.

Their shells are very sharp, which may cause cuts when people step on them.

Zebra mussels clog water supply lines and attach to motors and docks, he said.

They filter tiny food particles out of the water. That reduces the available food for larval fish and other animals, according to Johnson.

Zebra mussels also attach to and smother native mussels.

The invasive specie prefers sandy, rocky lakebeds.

The fact that Shadow Lake has a mucky bottom is a positive, said Aaron Jenson, Waupaca’s parks and recreation director.

“We’re hoping the geography of the lake will keep the population in check,” he said. “We will have to keep an eye on the beach, because it is a sandy area.”

He said the Parks and Recreation Department is used to checking for other invasives in the lake, including Eurasian Milfoil and Curly Leaf Pondweed.

Efforts for controlling those invasives include pulling them from the lake, including with the use of divers.

“There really are not any methods for controlling the zebra mussel population,” Jenson said.

After he informed the supervisor of the lifeguards about the discovery of zebra mussels in the lake, Jenson learned lifeguards have been scraping them off the diving dock area this summer and disposing of them in the garbage.

The lifeguards had not been aware they were zebra mussels, and Jenson said the lifeguards did the right thing in disposing of them in the garbage instead of putting them back into the lake.

That is how others who find them should also dispose of them.

There have been no complaints about them at South Park’s beach.

If people do see them by the beach, Jenson wants to know, because if it becomes an issue there in the future, they will recommend people wear swim shoes.

He encourages people to call the Parks and Recreation Department at 715-258-4435, if they see any zebra mussels in the beach area.

“If anybody from the public notices anything, we want to hear from them,” Jenson said. “We will keep a close eye on it. We want to know what people are seeing.”

The Friends of Mirror Shadow Lakes also wants to know if those who live or fish on the lake are seeing them.

Jenson said his department will keep in touch with the friends group and the DNR to monitor the situation.

During the past several years, the city’s parks department used Clean Boats, Clean Water volunteers and signage at the boat landing to educate boaters about how to prevent the spread of aquatic invasive species.

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