Select Page

Red Swamp Crayfish

Procambarus clarkii
Home 9 Invaders 9 Invertebrates 9 Red Swamp Crayfish

What is Ontario Doing?

To prevent this unwanted invader from coming into the province, Ontario has regulated red swamp crayfish as prohibited under the Invasive Species Act, 2015. For more information on the Invasive Species Act and Regulations, visit


Red swamp crayfish are large, aggressive crayfish native to the Gulf Coast and Mississippi River Basin in the United States. They present a significant threat to Ontario’s waters and have recently been reported in Lake Erie. Their spread can be attributed to accidental and intentional releases from aquaculture and the aquarium trade.


Red swamp crayfish can inhabit a variety of freshwater environments, such as ponds, lakes, swamps, streams, and ditches. The red swamp crayfish has spread widely throughout the United States and is present in states on the south-side of the Great Lakes, such as Ohio, Michigan, and Wisconsin.

For an up to date distribution of Red Swamp Crayfish in North America, visit

Impacts of Red Swamp Crayfish

  • May act as a vector of spread for diseases to native crayfish, such as the crayfish fungus plague.
  • By eating large quantities of aquatic vegetation, they reduce spawning and nursery habitat for native fish.
  • Crayfish are known to eat fish eggs and larvae, which can lead to decreased populations of desired sport fish.
  • They can quickly dominate lakes, ponds, rivers, and wetlands, causing significant environmental change and damage.
  • Female crayfish have the ability to carry between 100-500 fertilized eggs under their tail, which allows the crayfish to spread rapidly.

How to Identify Red Swamp Crayfish

  • Red swamp crayfish are large and can reach 5 to 13 cm from rostrum (part of shell in front of eyes) to tail.
  • Dark-red in colour with raised bright-red, white, or black spots (tubercles) that cover the body and claws.
  • Almost always have a blue-gray pigmented line on the underside of the tail.
  • Chelae (claws) are narrow and long.
  • Red swamp crayfish could be confused with many native crayfish species in Ontario, however, our species have much less pronounced tubercles, when present.

What You Can Do

  • Learn how to identify red swamp crayfish and how to prevent accidentally spreading invasive species.
  • If you want to use crayfish as bait, you may only use them in the waterbody in which they were caught. For more information on using crayfish as bait, check the Ontario Fishing Regulations.
  • If you have any information about the release of species, such as the red swamp crayfish, into Ontario’s waters, report it immediately to the MNRF TIPS line at 1-877-847-7667 toll-free any time, or contact your local Ministry of Natural Resources and Forestry office ( during regular business hours. You can also call Crime Stoppers anonymously at 1-800-222-8477.
  • If you’ve seen a Red Swamp Crayfish or other invasive species in the wild, please contact the toll-free Invading Species Hotline at 1-800-563-7711 or visit EDDMapS to report a sighting.

Resource Files


OFAH/OMNRF Invading Species Awareness Program. (2021). Red Swamp Crayfish. Retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Header photo by Alvesgaspar, wikimedia.


Reporting Invasive Species | Ontario's Invading Species Awareness Program

Think you have seen an invasive species?


Report it!


Invading Species Hotline



EDDMapS Logo

Available on the AppStore   Available on Google Play