MADISON, Wis. — The battle against the spread of aquatic invasive species took an unexpected turn on June 21, when red swamp crayfish were discovered at a Sauk Prairie canoe landing. The red swamp crayfish is illegal to possess and transport in the state. The last known collection of the species in Wisconsin was in 2009.

The DNR responded to multiple reports of live crayfish in the parking lot at the canoe landing on the Wisconsin River in Sauk City. Two department experts identified the species and collected as many crayfish as possible. DNR personnel also installed 1,000 feet of silt fencing and dug a trench to contain any live crayfish.

An additional 900 feet of fencing was installed a week later. Red swamp crayfish can travel several miles over dry ground and can burrow into the ground during extended periods of dry weather. The fencing will remain in place to contain any crayfish not captured during initial collection efforts.

Initial monitoring does not suggest that any of the dumped crayfish reached the Wisconsin River or other bodies of water in the area, but DNR said monitoring efforts will continue.

Investigators are trying to determine who dumped the crayfish. Anyone with information is asked to call the DNR tip line at 800-847-9367 or submit a report online at

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Red swamp crayfish are native to the coastal gulf region from the Florida panhandle to Mexico. They are dark red with raised bright red spots covering the body and claws. They have a black wedge-shaped stripe on the top of the abdomen. They are typically two to five inches long, though some specimens collected at the boat ramp were almost nine inches long.

The DNR believes the crayfish were introduced through aquaculture because they are a popular food worldwide. The species can be a host for parasites and disease, and can carry crayfish fungus plague. Once established, they aggressively compete with native crayfish and other species for food and habitat.

As with all aquatic invasive species, anglers can control their spread by:

  • Properly disposing of live crayfish and other unused bait in the trash.
  • Inspecting your watercraft, trailer, motor, equipment, clothing, boots and buckets for invasive species.
  • Removing visible mud, aquatic plants and animals before leaving any water access.
  • Draining water from your boat bilge, motor, jet drives, livewell and other equipment.
  • Never moving live fish or other animals and plants away from the body of water where they were caught.
  • Drying everything for at least five days before visiting other water bodies or spraying equipment with 140 degree water to kill invasive species.

The DNR species page offers more information on identification and control measures: