Two red swamp crayfish have been found in Tilde Lake in Clay County in northwestern Minnesota. It is the first time the species has been confirmed in a Minnesota lake, according to the Department of Natural Resources (DNR.)

The live specimen have been removed and DNR fisheries staff are searching the lake to see if there are any other that remain.

"Many aquarium animals and plans are invasive species that can cause serious harm if released into the wild," said Heidi Wolf, DNR invasive species unit supervisor.

Wolf said the red swamp crayfish is a good example of a prohibited invasive species that some online retailers ship to unsuspecting teachers for classroom aquariums or to people hosting crawfish boils.

Red swamp crayfish compete with native species for habitat and eat tadpole, snails, and other small aquatic animals. Their burrowing habits make them extremely difficult to remove and cause damage to levees, dams, and water control structures.

Prohibited species like the red swamp crayfish cannot legally be possessed, released into the wild, used as bait, or transferred to others. The recommended and most humane method of disposing of them is to put them into a plastic bag in the freezer for a day, and then put that bag into the trash.

For more information about prohibited and regulated species and what to do with them is available at www.dnr.state.mn.us/invasives/laws.html.