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At a previous news conference, DNR officials showed this example of zebra mussels clustered on a small tree branch that had fallen into Rice Lake near Brainerd.

David Brewster, Star Tribune

Zebra mussel larvae found in Lake Winnibigoshish

  • Associated Press
  • January 31, 2013 - 8:12 PM

ST. PAUL, Minn. - Invasive zebra mussels have likely established a breeding population in northern Minnesota's Lake Winnibigoshish that could spread down the Mississippi River, the Department of Natural Resources announced Thursday.

Officials have not yet found adult zebra mussels in the popular fishing lake, but two microscopic zebra mussel larvae, called veligers, were found in a water sample collected from the middle of the lake in mid-July, DNR officials told reporters. Fourteen other samples turned up no additional larvae, but DNR research scientist Gary Montz said the most likely explanation for the discovery is that adults are reproducing somewhere in the lake.

There's only a slight possibility that the veligers were accidentally dumped from a contaminated bait bucket or boat, Montz said. Given the small size of the sample and the immensity of the lake — Minnesota's fourth largest — the chance that they were released and then caught is remote, he said.

It's difficult to predict how fast the population will grow or how it will affect the lake's walleyes, northern pike, perch and other fish species, Montz said. Zebra mussel populations have grown quickly in some Minnesota lakes, but slowly in others.

Assuming the population builds, he said, eventually enough veligers will flow out of the lake that they could establish populations in other lakes and backwaters down the Mississippi as far as Brainerd, where they're already entrenched.

The DNR declared Winnibigoshish infested because of the threat. DNR spokesman Chris Niskanen said the agency will develop a boat inspection plan to try to stop zebra mussels from catching rides to other lakes, which is the main way they spread.

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