Five invasive species that threaten Minnesota waters

This bighead carp was caught on Lake Pepin in 2007
This bighead carp was caught on Lake Pepin in 2007
Photo: MN DNR

June 23 was probably like any other day for the 20-pound bighead carp. Meander through south Chicago's Lake Calumet. Eat a few pounds of plankton. Frighten some minnows. Excrete said plankton. But the Asian carp, six miles from Lake Michigan, was an unwitting fugitive, caught by federal officials beyond a multi-million dollar electric barrier built to prevent fish like this one from invading the Great Lakes.

The discovery helped prompt five states, including Minnesota, to sue the feds for failing to properly prevent their migration. Which prompts us to take a look at what other species have already invaded ecosystems in and around Minnesota waters. We're talking about angry swans and nasty tapeworms, folks. Check out the videos:

Asian Carp

Asian carp, depicted above, haven't arrived here yet. Hence the general hysteria (there has already been an Asian carp summit at the White House). We're stuck with the common carp, the ugly slobs. They release phosphorus, which increases algae levels. They also uproot aquatic plants, muddying the waters and depleting food the supply for other fish. If you want to party with some real carp--the leaping silver breed--Bath, Illinois is holding the Redneck Fishing Tournament on August 6th and 7th. Just don't say we didn't warn you about the confederate flags.

Mute Swan

Mute? Seriously? This is a badass swan. Brought from across the Atlantic for ornamental purposes, the mute swan is a creature of beauty and of folklore, one that you should stay the hell away from. This bird is veritably rowdy, not just toward people, but also the entrancing soloist of Minnesota, our state bird, the loon, which the mute swan can prevent from nesting. We shouldn't stand for this hissing bully, nor its potential to uproot 20 pounds of native aquatic plants per day. But it looks like we might have to: their population is increasing by a fifth annually near Lake Superior. Admire from afar.

Bass Tapeworm

"Mature tapeworm makes the bass unappealing for food," declares the Minnesota DNR, answering whether a tapeworm-infected bass is, in fact, safe for human consumption. Go on, state the obvious: "Even though the eating quality of the fish is not affected and there is no human danger if the fillets are cooked thoroughly." Hungry?

Sea Lamprey

Like the tapeworm, the sea lamprey is also a parasite. These eel-like, aquatic vampires are predacious, living off the fish they attack for days. Some estimates peg their kill rates at six out of seven fish they attack. By the 1960s, sea lamprey populations almost wiped out the trout populations in lakes Superior and Huron. Since then, though, we've partnered with Canada in conducting an ongoing lampricide--chemical warfare!--and their populations have been decreased by roughly 90 percent. Still, if they're not sucking blood, they're sucking money, costing some $16 million annually to control.


Lo, the lowly earthworm. The 15 invasive earthworm species in Minnesota deplete duff like Homer Simpson. Duff, in this case, is the layer of organic, spongy material on forest floors that helps woodland wildflowers and tree seedlings grow. Duff, says the state's DNR, also provides a habitat for ground-dwelling animals and prevents soil erosion. Addressing the seeming futility of preventing invasive earthworm abundance in the state--you can't go to a gas station outside the suburban ring that doesn't sell night crawlers, which are invasive--the DNR asks: "If non-native earthworms are already here, isn't it already late?" Apparently not with how slow their populations move: a half mile every 100 years. Just keep them out of the duff.

Sponsor Content


All-access pass to top stories, events and offers around town.

Sign Up >

No Thanks!

Remind Me Later >