Red swamp crayfish a threatening guest in Ontario waters

Invasive species found in Tilbury, Ont., and Lake Aquitaine in Mississauga

Published Jun 17, 2026  •  Last updated 47 minutes ago  •  2 minute read

The red swamp crayfish. Native to the U.S Gulf Coast and the Mississippi River basin, this invasive species has been found in southern Ontario. Photo by Luc Hoogenstein, Wikimedia Commons

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Ontario residents are duly warned about an invasive species that is rapidly gaining a foothold in some southern Ontario waterways. 

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“This invasive species is considered a global invader and is highly destructive to wetlands and shorelines and will outcompete native crayfishes and other aquatic wildlife,” the Ontario Federation of Anglers and Hunters (OFAH) said in a social media post earlier this year in reference to the red swamp crayfish.  

Last summer, the Invasive Species Awareness Program (ISAP) conducted a survey in Tilbury, Ont. More than 100 red swamp crayfish were found. The province says the species hasn’t been found in Ontario waters just yet, though they do recognize the species as a threat to native species.  

The OFAH also says the species has been found in localized areas in Mississauga’s Lake Aquitaine.

It is illegal

Red swamp crayfish are native to the Gulf Coast region and the Mississippi River basin. Females may carry about 100 to 500 fertilized eggs under the tail, causing populations to grow quickly. Termed as an “aggressive” crayfish, they are found in various freshwater habitats with muddy or sandy bottoms and a large amount of organic debris. 

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The OFAH, the ISAP and Fisheries and Oceans Canada offer an online resourceto help identify the differences between native and non-native crayfish. 

It is against the law to import live, possess, deposit, release, transport, breed/grow, buy, sell, lease, or trade red swamp crayfish in Ontario. 

Cash infusion

On Monday at Lake Simcoe, the province announced a $2 million investment to help municipalities, Indigenous communities, conservation authorities and local organizations stop the spread of harmful invasive species. 

“From early invasive species detection to on-the-ground management, this investment is helping communities across the province protect the natural spaces we all rely on and enjoy,” Dawn Gallagher Murphy, Parliamentary Assistant to the Minister of Natural Resources said. 

Monday’s announcement is part of the three year, $16-million investment by the province to fight against the spread of invasive species. 

The Ontario Invasive Species Act currently lists 42 species, four groups, one family and two carriers as invasive. The Act provides legislative tools to prohibit and restrict certain invasive species, as well as highlighting carriers that facilitate the movement of invasive species. 

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The province says Ontario has the highest number of invasive species in Canada. Once established, an invasive species can harm the natural environment and are extremely difficult and costly to control or remove. 

“The best way to protect Ontario from invasive species is by preventing them from spreading,” Mike Harris, Minister of Natural Resources said. “That’s why our government continues to invest and give communities the tools they need to keep our waterways and forests safe for families across Ontario to enjoy.” 

The province of Ontario defines an invasive species as “a species that is not native to Ontario, or to a part of Ontario and, is harming the natural environment of Ontario in which it is present or is likely to harm the natural environment of Ontario or of a part of Ontario, regardless of whether it is present in Ontario or in a part of Ontario.” 

If you think you’ve found a red swamp crayfish, report it by calling the Invading Species Hotline at 1-800-563-7711   

[email protected]

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