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 bumps on the body and claws. Bumps on the claws are often red in color.
• Hourglass shape on the back touches in the middle. 
• The tail typically has a dark wedge-shaped color pattern on it when seen from the top.
• Individuals are typically shades of dark red, brown and black. Small individuals are typically brown and mottled. Individuals from the pet trade can come in other unusual colors (blue, orange, cow print, white, etc.), and solid white individuals have been found in Michigan waters. 
• Claws are long and thin compared to many other species. Described as “saber” shaped.
• Generally 2 to 4 inches but can grow as large as 6 inches long.
• 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: Crayfish feed heavily on snails, fish, amphibians, and plants.

Native Range: Mississippi river drainage and Gulf Coast.

U.S. Distribution (outside of native range): Established populations in California, Delaware, Illinois, Maryland, Michigan, Ohio, Oregon, South Carolina, Utah, Virginia, Washington, and Wisconsin. Introduced but not established in Alaska, Hawaii, Idaho, Indiana, Nevada and New York.

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