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Signal Crayfish

Pacifastacus leniusculus
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What is Ontario Doing?

To prevent these unwanted invaders from coming into the province, Ontario has regulated the Pacifastacus genus as prohibited under the Invasive Species Act, 2015.


The Genus Pacifastacus includes six crayfish species native to western North America. The signal crayfish, Pacifastacus leniusculus, native to the Columbia river basin, is at risk of being introduced to Ontario, where it is invasive. Signal crayfish can be introduced to Ontario from anglers bringing the crayfishes from their native range to use as bait or can be released from aquarists.


Signal crayfish is native to the northwestern United States within the Columbia river basin. Their northern distribution includes Washington, Oregon, Idaho and southern British Columbia, their southern range includes Oregon’s coast.  

For an up to date distribution of signal crayfish in Ontario, visit 

Impacts of Signal 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. 
  • Can exploit a variety of freshwater ecosystems and compete with native crayfishes and other aquatic species. 

How to Identify Signal Crayfish

  • Dorsal surface is reddish-brown in colouration. 
  • Bright red colouration on the underside of the claws and a white or turquoise colored patch at the base of each claw. 
  • Carapace surface is smooth. 

What You Can Do

  • Learn how to identify Pacifastacus crayfishes 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 signal 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 signal 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.


OFAH/OMNRF Invading Species Awareness Program. (2023). Signal Crayfish retrieved from:
This factsheet may be reproduced for non-commercial purposes.

Header photo by USFWS-PacificRegion | WikiMediaCommons 

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