What Ontario is doing

To prevent these unwanted invaders from coming into the province or spreading further, Ontario has regulated all species in the genus Procambarus as prohibited invasive species under the Invasive Species Act.

Learn about the Invasive Species Act and regulations.

Background

Procambarus is a genus (closely related group) of freshwater crayfish that includes more than 160 species. They are mostly native to the Southern United States and Northern Mexico.

Some crayfish in this genus are very adaptable, which means they can thrive in many types of aquatic environments like:

  • slow-moving rivers
  • swamps
  • agricultural water systems
  • urban water systems

Procambarus species can become invasive when introduced outside their native range, where they cause substantial disruption to local biodiversity.

All species of crayfish within the Procambarus genus are prohibited invasive species. Notable species include:

  • Procambarus clarkii (red swamp crayfish): this species is known for its aggressive behaviour, rapid reproduction and ability to disrupt local ecosystems through burrowing and outcompeting native species.
  • Procambarus virginalis (marmorkrebs or marbled crayfish): unique for its parthenogenetic reproduction (cloning), the marbled crayfish can quickly dominate water bodies and overwhelm native species.
  • Procambarus acutus (white river crayfish): can adapt to various water conditions, displacing native crayfish and causing environmental disruptions.

These species can thrive in diverse environmental conditions, including:

  • clear or turbid (cloudy) waters
  • variable oxygen levels
  • temperatures ranging from 5°C to 30°C

Their adaptability and ability to eat a variety of food worsens their negative impacts when they invade new ecosystems.

While no longer allowed in Ontario, Procambarus species are available for sale online in other jurisdictions for aquaria, research or consumption.

Procambarus species may also be unlawfully listed for sale in Ontario or illegally used as bait by anglers, leading to intentional or accidental releases.

Range

All species of Procambarus crayfish are native to North and Central America.

Most of the species are found in the Southeastern United States, but some Procambarus species are found as far south as:

  • Guatemala
  • Honduras
  • Cuba  

Several species of Procambarus have been introduced to regions outside their native range, both in North America and other continents including Europe, Asia and Africa. 

White river crayfish was first found in Ontario on Pelee Island in 2015. 

In 2023, marbled crayfish was found near Burlington, Ontario. This is the first known occurrence of this species in Canada outside of captivity.

View an up to date distribution map of Procambarus species.

Impacts of Procambarus species

Some species of Procambarus crayfish are known to cause significant ecological impacts by:

  • feeding on plants, invertebrates and small fish, altering local food webs
  • outcompeting native crayfish and other aquatic species for food and habitat
  • burrowing behavior, causing erosion, making the water murkier and degrading habitats

These disruptions to aquatic habitats can have negative effects on native fish, invertebrate populations and reduce biodiversity.

How to identify Procambarus

Marbled crayfish

  • A medium-sized crayfish that is 3 to 10 centimetres in length.
  • Body can be dark brown, tan, brown-green or sometimes blue, always with marble patterning.
  • Juveniles (young) develop spotted pigmentation and have more marble patterning in adolescence.

Red swamp crayfish

  • The adult crayfish are 5.5 to 12 centimetres long. The adult’s body is also dark red and the claws and head are elongated. 
  • Some individuals in the aquarium trade are bred to be different colours, such as blue. 
  • The head, claws and mid-body segment are covered in small red bumps.

White river crayfish

  • Large crayfish, typically about 7 to 13 centimetres in length.
  • Adult body colour is brown to grey with a wide black stripe on the tail.
  • Juveniles (young) are sandy-white, with black spots on the head, body and tail.
  • Has asymmetrical claws, typically with a larger right claw.

What you need to know

  • Learn how to identify species in the Procambarus genus and how to prevent the introduction or spread of these crayfish to local waterways.  
  • It is illegal to import, deposit, release, possess, transport, propagate, buy, sell or trade species in the Procambarus genus in Ontario. Only red swamp crayfish (Procambarus clarkii) and white river crayfish (Procambarus acutus) which are dead and prepared for human consumption may be imported, transported, bought or sold in Ontario.
  • Never buy or use Procambarus species for an aquarium, bait, or any other purpose.  
  • If you possessed crayfish in the Procambarus genus on January 1, 2024, the regulation came into force, you may continue to possess and transport them until January 1, 2026 (except for marbled crayfish and red swamp crayfish). This transition period provides time for you to become aware of the rules and dispose of the crayfish. Before January 1, 2026, you must kill the crayfish and dispose of it in a way that ensures it does not spread (for example, by freezing them and placing into the garbage).
  • If you are in possession of a species in the Procambarus genus and would like to learn more about what you need to do, email us at invasive.species@ontario.ca.
  • Never release any live organisms into Ontario waterbodies. 

Reporting illegal activity

If you have any information about the illegal importation, distribution, or sale of any Procambarus species, report it immediately to either:

If you’ve seen a Procambarus species or another invasive species in the wild, please: