GRAND RAPIDS, Mich. (WOOD) — Michigan environmental officials are turning to radio telemetry and modified shower loofas in their fight to contain a tasty invader in the state.

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(A sign posted at Sunset Lake in Kalamazoo County warns of red swamp crayfish found in the water.)

The red swamp crayfish was first discovered dead on Lake Macatawa’s banks in 2013. Four years later, Sunset Lake in Vicksburg became one of the first places the invasive species turned up alive.

Since then, the Michigan Department of Natural Resources, Michigan State University, the Gun Lake Tribe and the Barry-Calhoun-Kalamazoo Cooperative Invasive Species Management Area have teamed up to fight the invader. Together, they’ve captured more than 900 red swamp crayfish in Sunset Lake and a nearby stream, mostly through backpack electrofishing, netting and spearing, according to Dr. Lucas Nathan, aquatic invasive species coordinator for the MDNR’s fisheries division.

(A photo provided by Dr. Lucas Nathan shows Brennan Wright pulling a trap.)

MDNR and MSU researchers say the red swamp crayfish has also surfaced in 28 other lakes, ponds and streams in southeast Michigan.

In a Tuesday webinar, Nathan said in 2017, teams caught 5,718 red swamp crayfish, mostly in the 1,926 traps they baited with dry dog food. That number exploded to 36,534 red swamp crayfish and 31,987 traps last year. While the pandemic hampered trap setting and active catch efforts this year, crews nonetheless captured 38,017 red swamp crayfish.

“So this is not an issue that’s going away,” said Dr. Brian Roth of MSU’s Department of Fisheries and Wildlife.


While they’re a staple in Southern seafood boils, red swamp crayfish pose a lot of problems for Michigan, starting with the parasites and diseases they may host.

(An undated photo provided by Dr. Lucas Nathan from the Michigan Department of Natural Resources shows a red swamp crayfish resting on a hand inside a laboratory.)

The Midwest Invasive Species Information Network says the invader’s diverse diet of plants, insects, snails, fish and amphibians can also impact the ecosystem. With the potential to grow to nearly 9 inches, the aggressive red swamp crayfish can crowd out native crayfish for food and habitat or kill them off with the crayfish fungus plague the red swamp crayfish can carry.

Michigan’s wetlands are at risk as well. Dr. Lucas Nathan with the MDNR says the extensive network of tunnels the crayfish create make “Swiss cheese of shorelines,” which can completely drain wetlands in extreme cases.


While there are uncertainties about how the red swamp crayfish made it into Michigan’s waters, research suggests different groups of people who independently released it may be the culprits. MSU experts say varying genetic markers in the captured crayfish support the theory.

Early on into the crayfish’s discovery, a team of MSU researchers surveyed 125 businesses and roughly half of the pet shops and 10% of live food markets carried the crustacean.

None of the bait shops surveyed carried red swamp crayfish, which the state outlawed as bait in 2013. However, Nathan says there’s anecdotal evidence that anglers may have bought the crayfish from live food markets and used them as bait.

(An undated photo provided by Dr. Lucas Nathan from the Michigan Department of Natural Resources shows a red swamp crayfish inside a laboratory.)

Additionally, the researchers found 11% of classrooms used red swamp crayfish. Approximately three out of four classrooms’ handling the crayfish was labeled as “risky use” that could lead to its spread.

In 2015, Michigan began prohibiting the possession of living red swamp crayfish. Combined with ramped up inspections and outreach efforts, Nathan says the number of red swamp crayfish in Michigan’s live trade industry has dwindled.


Roth says “the big question” now is whethery they can eradicate red swamp crayfish from the warmer bodies of water where they’ve been found. The team says the most effective method will likely include a combination of trapping, chemical and biological tactics.

MSU researchers are testing out findings from MSU’s biosystems engineering department that the crayfish are attracted to white noise. The biosystems engineering team led by Dr. Wei Liao is now using MRI scans to see how the red swamp crayfish’s brain responds to sound.

“Dr. Liao is a mad genius, I’ve got to say,” Roth remarked during a Tuesday webinar about the invasive species.

(An undated courtesy photo presented by the Michigan Department of Natural Resources and Michigan State University show red swamp crayfish, including one wearing a radio tracking device.)

MSU researchers have additionally tested out a variety of traps, including modified loofas to capture young, smaller red swamp crayfish that slip through other traps. Nathan says the loofas provide plenty of nooks and crannies for the juvenile crayfish to hide.

They’re also strapping radio devices to the crayfish to track their movement, exploring how they can manipulate where the crayfish go by pumping carbon dioxide into the water, researching the species further to figure out what they do during winter, analyzing whether introducing crayfish-eating panfish or small mouth bass could help and looking into possibly heating small lakes and ponds so they can trap red swamp crayfish year-round.

The experts say they’re also waiting on permit approval from the Michigan Department of Environment, Great Lakes, and Energy to use a pyrethrin, the same organic compound the state used in aerial treatments to kill off mosquitoes carrying Eastern Equine Encephalitis. The EPA already approved the new use.


  • Clean, drain and dry any watercraft before moving it into another lake.
  • Throw out unwanted fishing bait and aquarium animals in the trash.
  • Remain vigilant. The first step to combating red swamp crayfish is identifying where they’re located. The invasive species has a dark red body, claws with spiky bright red bumps and a black wed-shaped stripe on their underside. Roth says red swamp crayfish burrows “look like someone had a No. 2 accident right all over the side of the pond.”
  • Report any suspected red swamp crayfish to the state by calling Nathan at 517.599.9323 or online at Reports should include the time, date and location of the sighting as well as a photo, if possible.