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Unwelcome resident: The red swamp crayfish is Minnesota's newest invasive species

Two red swamp crayfish were discovered in a Minnesota lake, marking the first time the invasive species has been confirmed in the state.

Meet Minnesota's newest invasive species: the red swamp crayfish.

Two of them were found in Tilde Lake in northwestern Minnesota, and the state Department of Natural Resources said Thursday it's the first time the freshwater crustacean has been confirmed in a Minnesota lake.

The crayfish, which are typically found in Louisiana, compete with native species for habitat. Plus, they burrow, so it makes them "extremely difficult" to remove, and the habit can cause damage to levees, dams and water control structures.

DNR fisheries staff have removed the two crayfish from the lake, and they're looking to see if there are any others that have taken up residence.

How'd they get there?

Red swamp crayfish are a prohibited invasive species in Minnesota. It's illegal to import or have one if you don't have a proper permit, the DNR says.

Despite them being illegal, sometimes they get here.

The crayfish, which are red in color and can grow to be about 5 inches long, are popular bait to catch largemouth bass, and are also often purchased to use in aquariums – they're advertised as "freshwater lobster," according to the U.S. Geological Survey.

The DNR says retailers will often ship the crayfish to teachers for their classroom aquarium or to people who want them for a crawfish boil, without the buyer realizing it's illegal to have them.

“We recommend teachers check the prohibited invasive species list before committing to classroom aquarium animals,” Wolf said. “We also encourage teachers to discuss invasive species with their students.”

And when people are done with the animals, sometimes they're released or flushed down the toilet, the U.S. Geological Survey notes. That's when problems can really start, with the DNR noting many aquarium animals or plants can cause serious harm to plants and animals that are native to Minnesota.

Instead of just letting a crayfish go, the DNR says putting them in a plastic bag in a freezer for a day and then throwing them in the trash is the most humane way to dispose of them.

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