The Minnesota Department of Natural Resources confirmed rusty crayfish were discovered in the Vermillion River in Farmington and Hastings. Rusty crayfish were also found in North Creek in Farmington.

The Vermillion River Watershed Joint Powers Organization’s routine biomonitoring carried out by the Dakota County Soil and Water Conservation District led to the discovery of three rusty crayfish in Farmington. Hastings High School students participating in the VRWJPO’s Vermillion River Watch program collected five rusty crayfish in the Vermillion River Linear Park.

Rusty crayfish are aggressive invaders. They harm fish populations by eating their eggs and young, driving out or crossbreeding with native crayfish, and grazing on and eliminating aquatic plants. Rusty crayfish compete with fish for food by preying on macroinvertebrates such as mayflies, midges, and scuds. The release of a single female could establish a new population.

Rusty crayfish are most likely spread through dumping bait buckets and aquariums.

It is a Department of Natural Resource-regulated invasive species, which means release into the wild is illegal. Licensed anglers may collect crayfish for use as bait on the same body of water where the crayfish were caught. They can also harvest up to 25 pounds of any crayfish for personal consumption. Selling live crayfish for bait or aquarium use is illegal.

Adult rusty crayfish are usually 3 to 5 inches long. A visible identifier on these olive-colored crayfish is a rust-colored spot on each side of its body. These spots may be lighter in color on younger crayfish. Rusty crayfish may breed with native crayfish, producing a hybrid without the usual rusty spots. They have more robust claws than native crayfish.

The best method of control is to prevent their introduction. Inspect and remove aquatic plants and animals from watercraft and recreational gear. Dispose of unwanted bait in the trash. Never release crayfish, fish, or plants from one body of water into another.