Some unwanted aquatic visitors are bringing a little Cajun flavor to lakes and ponds around Michigan this summer.
The Michigan Department of Natural Resources confirmed the presence of the invasive red swamp crayfish, also known as Louisiana crayfish, in Sunset Lake in Vicksburg on the state's west side and a retention pond off Haggerty Road in Novi.
Two separate landowners reported the crayfish at Sunset Lake to the DNR on July 13, and the agency surveyed the site the next day and found several crayfish in the grass of a local park and in shallow areas of the lake’s west side, according to a DNR news release.
The agency removed 111 specimens from a retention pond in Novi on Monday after a child captured one in a dip net.
The two reports were the first live detections of red swamp crayfish in Michigan, according to the DNR.
Red swamp crayfish, which are 2-5 inches in length and look like miniature lobsters, are native to the Mississippi River drainage and gulf coast, according to the news release.
The sources of the two infestations are not known, the agency said, and live crayfish may have been brought from Southern states for use as bait or for human consumption.
“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,” Nick Popoff, aquatic species and regulatory affairs manager for the DNR, said in a statement.
Popoff said there are eight kinds of native crayfish in Michigan and that the invasive red swamp crayfish can outcompete other crayfish because they tend to grow large and are aggressive. He said when crayfish meet they tend to kill each other — even those of the same species.
The red swamp species is considered invasive in Michigan because they disrupt the food chain for many aquatic species by feeding on plants, insects, snails, juvenile fish and other crayfish, according to the news release.
“Red swamp will cause decline in native populations of crayfish,” Popoff said in a phone interview.
The other invasive species in Michigan is the rusty crayfish, which arrived decades ago from the Ohio River drainage area and today is the most abundant crayfish species in Michigan, according to a 2015-2016 study that covered only part of the state, Popoff said.
Popoff said he’s no crayfish connoisseur but, from what he knows, they all taste the same.
“I don’t think they taste any better, there’s just more of them out there,” Popoff said of the red swamp variety.
The red swamp crayfish also pose a threat to the environment, the DNR said. The agency reported that the species is “a serious concern because of their ability to damage earthen structures and the threats they pose to the environment.”
Their burrows can be more than 3 feet deep and cause damage through bank destabilization to infrastructure such as dams, levees, irrigation systems and personal property, according to the news release.
Popoff said properties across the street from and adjacent to Sunset Lake reported burrows in their yards.
Red swamp crayfish are unique, he said, because they will travel on land to feed and can drill down to the water table.
The native species do not cause that kind of environmental and property damage, Popoff said.
He said the creatures, which spread via tributaries and over land, are challenging to eradicate and that one of the department’s primary goals is to contain them and determine how they’re going to spread.
He said the department uses baited crayfish traps, dip nets and electrofishing to capture and remove the crayfish. Electrofishing puts a current in the water which stuns the creatures without killing them and allows them to be caught.
Afterward, the crayfish are put in ethanol alcohol, which preserves them if they’re needed for any further evaluations, Popoff said.
“There’s not many success stories with invasive species eradication,” Popoff said.
Popoff said that there’s no good way to age crayfish and that they can’t estimate how long the red swamp crayfish have been in Michigan.
The DNR said it will continue its survey and removal efforts on Sunset Lake and its tributaries to determine the size and extent of the infestation. Connecting bodies of water, including Austin, Barton, and Howard lakes will be surveyed in the coming weeks.
Survey and removal efforts are also ongoing at the Novi location, DNR reported.
The DNR said that sightings should be photographed and reported with the date and location of the find to firstname.lastname@example.org.
Popoff said that people are asked to bag the crayfish, freeze them, and call DNR.
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