Red Swamp Crayfish & Marbled Crayfish

Harmful Impacts

Red swamp crayfish (RSC) and marbled crayfish compete aggressively for food and habitat with native amphibians, invertebrates, and juvenile fish. Burrowing and foraging behavior can also lead to erosion, summer cyanobacteria blooms, and eutrophic conditions.

Both crayfish are on the Michigan invasive species watch list and are prohibited species, which means it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism.

Local Efforts

RSC were discovered in Shelby Township in 2019. In 2021, the CISMA spent an estimated 700 hours performing landowner outreach, surveys and removal efforts. In total, over 450 invasive RSC were removed from local, public waters.

The CISMA will continue early detection and rapid response efforts in 2022. Specific county drains, ponds, and lakes in Shelby Township will be targeted. Survey and removal efforts can only take place where landowner permission is provided. To provide permission, please email

How You Can Help

Red swamp crayfish

  • Dark red color or olive with bright red raised spots

  • Closed carapace (two plates on back touch)

Native look-alikes:

  • Devil crawfish: mostly tan body with red highlights around head, body, and claws

  • White river crayfish: color may vary from tan to rusty red color, no bright red bumps

Marbled crayfish

  • Not yet detected in Michigan

  • Marbled color pattern most visible on its carapace or back

  • Coloring is generally olive to dark brown but can be tan to reddish to blue

  • Reproduces through parthenogenesis (i.e., ability to self-clone)

    • all individuals are female

    • up to 700 unfertilized eggs that develop into genetically identical offspring

If you see marbled crayfish in the wild, take one or more photos and make note of the location, date and time of the observation, and report to:

Lucas Nathan, DNR Fisheries Division, 517-599-9323

Native look-alikes:

  • Calico crayfish: small (2” to 3.5”) and generally grayish-green in color. Claw tips or pincers are orange, and purple-tinged in adult males.

  • White river crayfish: have larger, more rounded claws. Both claws and carapace are covered with raised bumps or tubercles.