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Invasive red swamp crayfish have been detected in a retention pond in Novi and in a lake south of Kalamazoo, posing a threat to native crayfish and the state’s natural environment, state officials said Wednesday.

The Michigan Department of Natural Resources said a citizen told state officials Monday about the possibility of the red swamp crayfish in a retention pond off Haggery Road after a child found one in a dip net. State officials went there the same day and found 111 of the two-inch to five-inch-long crayfish that look like miniature lobsters.

The other red swamp crayfish was found in Sunset Lake by two separate landowners, state officials said.

State officials say these are the first “live” detections of red swamp in Michigan.

“Eradicating red swamp crayfish is very difficult,” said Nick Popoff, the DNR’s aquatic species and regulatory affairs manager. “They dig deep burrows near lakes and rivers and can spread quickly over land.”

The state Department of Natural Resources seems alarmed by this development because the crayfish that are native to the Gulf Coast can kill native crayfish while damaging irrigation systems and personal property as well as destabilizing river banks by digging 3-foot-deep burrows. They also can spread quickly over land, having a range of up to two miles, according to the state agency.

These crayfish generate concern because they can harm the environment and have the “ability to damage earthen structures,” according to the DNR.

They are considered invasive because they compete with the native crayfish and feed on plants, insects, snails, juvenile fish that removes the food chain for many aquatic species. They also can survive drought, according to the DNR.

One Wisconsin pond was so infestated that officials took the extreme measure of paving over the pond to try to stop the spread of the red swamp crayfish, the DNR said.

DNR officials aren’t sure how the crayfish got in the pond and lake. But Popoff speculated that live crayfish may have been brought from Southern states for eating or to use as bait. They also could have been released from other states where their sale is legal as personal or classroom aquarium pets, he said.

“Red swamp crayfish are a prohibited species in Michigan, which means it is unlawful to possess, introduce, import, sell or offer them for sale as a live organism, except in special circumstances, including providing specimens to the DNR for identification,” Popoff said.

State officials are surveying the Novi retention pond for other crayfish and removing any others they find.

DNR staffers also are continuing removal of the red swamp crayfish in Sunset Lake as they survey the lake and its tributaries to determine the extent of what they call an “infestation.” The agency said it plans to survey connecting waterways and bodies including Austin, Barton and Howard lakes in the next few weeks.

DNR officials encourage the public to report any sightings of the crayfish and capture and freeze them if they can. Photographs of any in the Novi area are welcome. The invasive crayfish are deep red with bright red, raised spots covering the body and claws.

The public can report their findings to the DNR at 269-685-6851, extension 0, or by email to herbsts1@michigan.gov.

lfleming@detroitnews.com

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