Signal crayfish, an invasive nonnative freshwater crustacean species, have been found in a western Minnesota lake, according to the state Department of Natural Resources.

The DNR said Friday that this is the first confirmation of signal crayfish in Minnesota waters.

A commercial harvester trapped two of the crayfish in Lake Winona, adjacent to Alexandria in Douglas County. Since then, the harvester found eight additional signal crayfish in the lake. The DNR set traps but was unable to find any other crayfish. Out of the 10 the harvester caught, there was one female out of the 10 and there was no evidence of reproduction, meaning no eggs or juveniles were found.

“Signal crayfish are larger and more aggressive than Minnesota crayfish and the invasive rusty crayfish,” the DNR said in a statement. “They eat aquatic plants, detritus, fish eggs, smaller crayfish species and other beneficial native invertebrates. Signal crayfish might outcompete native species for food and habitat. Signal crayfish can spread between connected waterways or be transported by people. They can also crawl over land at night and during wet weather.”

Importing the crayfish is illegal without a permit, a DNR biologist said.

“Regardless of species, it is illegal to release non-native plants or animals into the environment,” said DNR aquatic invertebrate biologist Don Eaton. “We deeply appreciate that people harvesting crayfish are keeping a close watch on their catch and that, in this case, the harvester quickly reported this unusual-looking crayfish to the DNR.”