Invasive Species: Red Swamp Crayfish

Red Swamp Crayfish

(Procambarus clarkii)

Detected in Michigan

WATCH LIST - PROHIBITED IN MICHIGAN

Report this species to:

Identification:

• Covered in many, often red bumps on the body and claws. 
• Hourglass shape on the back touches in the middle. 
• Dark triangle on tail.
• Body can be shades of dark red, brown, black or even all white. Individuals from the pet trade can come in other unusual colors (blue, orange, cow print, white, etc.). Small individuals are typically brown and mottled.
• Claws are long, thin and saber-shaped.
• Generally, 2 to 4 inches; can grow to 6 inches.
• Refer to the Field Guide to Michigan Crayfish and the Great Lakes Almanac to Invasive Crayfish Identification & Reporting for more details.

Red swamp crayfish identification key. Illustration by Joseph R. Tomelleri.

Photo courtesy of Saxifraga - Rudmer Zwerver.

A white-colored red swamp crayfish found in Livingston County. Photo taken by Roth Lab at MSU and Aaron Sullivan.

Habitat: Red swamp crayfish live in a variety of permanent freshwater habitats. Crayfish are crustaceans that burrow deep into the substrate of their habitat and create large mounds of sand and soil called chimneys with a relatively large hole in the center.

Diet: Omnivorous and feed opportunistically on snails, invertebrates, fish, amphibians and aquatic plants. 

Native Range: Mississippi river drainage and Gulf Coast.

U.S. Distribution (outside of native range): Populations are present in most states, with more widespread areas of infestation in the southeast.

Michigan Distribution: Red swamp crayfish populations have been confirmed in Kalamazoo, Livingston, Macomb, Oakland, Van Buren and Wayne counties in Michigan. 

A map of counties where red swamp crayfish has been detected in Michigan.

Local Concern: Their burrowing behavior can cause erosion issues on banks when at high densities. Red swamp crayfish can outcompete and have negative effects on native crayfish, amphibians, invertebrates and juvenile fish due to their aggressive behavior and high reproductive rates. They can be particularly destructive to aquatic plants which can cause water quality and clarity issues, cyanobacteria blooms and eutrophic conditions.

Other Names: Louisiana crayfish/crawfish.

Potential Means of Introduction: Aquaculture/aquarium trade, classroom/laboratory release and live bait dumping.

Native look-alikes and how you can tell them apart from red swamp crayfish:

• Great Plains mudbug: Wide claws, smooth body without numerous bumps, no spines on either side of the tip of the rostrum (nose-like structure).
• White river crayfish: Looks extremely similar. White river crayfish has an hourglass shape on its back that does not touch in the middle. Additionally, bumps on the claws are typically white or black.

MORE INFORMATION:

• Red Swamp Crayfish Invasive Species Alert (printable PDF)
• Crayfish of Michigan Poster
• Great Lakes Almanac to Invasive Crayfish Identification & Reporting:
  • English version
  • Hmong version
  • Simplified Chinese version
  • Spanish version
• Field Guide to Michigan Crayfish
• Red swamp crayfish information for educators 
• Video: Michigan Crayfish Regulations & Recipe