DNR: Invasive water flea hasn't hurt Lake of the Woods

Spiny water fleas
Spiny water fleas are considered invasive species. They were found in Lake of the Woods in northern Minnesota a few years ago, but so far their numbers have been contained.
Photo courtesy of Michigan Sea Grant

It's been two years since the invasive spiny water flea was confirmed in northern Minnesota's Lake of the Woods, but state experts say they haven't seen negative effects yet from the species.

The species came to North America from Europe in the ballast water of Great Lakes ships. It was reported in the Rainy River watershed in 2006, and by the spring of 2007, the Department of Natural Resources had declared Lake of the Woods, Rainy River and other lakes and rivers in the watershed infested.

Spiny water fleas, a type of plankton, compete for survival with native zooplankton, which walleye and other northern fish need to survive.

The spiny water flea, characterized by a large spiny tail, has little nutritional value for fish, and its arrival caused a scare in a region where the economy relies on fishing.

But Tom Heinrich, a large lake specialist for the DNR, said his testing has yet to measure much, if any, impact.

"It doesn't seem like they're becoming more abundant," said Heinrich, who's based in Baudette.

Lake of the Woods
A map showing the location of Lake of the Woods, which sits partly in Minnesota and partly in Canada.
Map © Wikipedia User:Indefatigable, via Creative Commons

Lake of the Woods has a large population of fish called tullibees that can feed on all types of plankton, and that may be keeping the spiny water fleas in check, he said.

"It's so dependent on the fish community that they're invading, and if you have a very robust community, in some cases, they don't have a huge impact because there's no niche for them to move into," Heinrich said.

In fact, locals have reported a great summer for fishing on Lake of the Woods.

But Heinrich warned anglers should take spiny water fleas and other invasive species seriously - keeping boats clean, drying out anchor ropes and landing nets and following regulations to prevent their spread into new waters.


Information from: Grand Forks Herald, http://www.grandforksherald.com