invasive crayfish ontario

Several species of lobster-like creatures spreading and causing havoc across Ontario

Several species of invasive crayfish are spreading across Ontario at worrying speed, and these small lobster-like crustaceans are already wreaking untold destruction on aquatic ecosystems in the province.

Invasive crayfish species have been a growing problem in the province for several years, out-competing native aquatic species for resources and stripping away bodies of water of vital life by rapidly feeding on algae and plants, as well as preying on invertebrates and amphibians.

The most common invasive species in Ontario is the rusty crayfish, a large freshwater species native to the United States, known for its aggression.

Rusty crayfish pose a threat to native species present within waterways across the province, including in the heart of urban environments like Toronto.

In 2020, a video showing native crustaceans in Toronto's Etobicoke Valley Park went viral on social media. However, these local species could soon be displaced by invaders that reproduce and eat at much faster rates.

It's an escalating problem that officials have responded to with new bans and restrictions as recently as this year.

At the beginning of 2024, the province banned the Procambarus genus of crayfish (with 161 known species) and the Pacifastacus genus (four living species). As of January 1, 2024, it is illegal to import, possess, deposit, release, transport, propagate, buy, sell, lease, or trade these types of crayfish.

Ontario's latest bans follow the 2023 arrival of perhaps the most worrying crustacean invader of the bunch. Known as the marbled crayfish (Procambarus virginalis), this mutant off-shoot got its start as an aquarium species in 1995 before breaking out into natural settings.

The species exists via a freak mutation that gives it a unique self-cloning ability, allowing a single animal to multiply into an enormous, exponentially-expanding population.

These all-female crayfish — which appear similar to lobsters but with a smaller, grey, marbled appearance — were first confirmed in Ontario last summer by Canada's Ministry of Natural Resources and Forestry (MNRF).

The MNRF announced via press release in August 2023 that a marbled crayfish was found in a pond in the Burlington, Ontario area, the first discovery of the species in the wild in the country.

Only two reports of the species in Ontario have been posted to the social network biodiversity app, iNaturalist, both of which were located in Burlington.

Platforms like these are valuable for identifying potential invaders and flagging their presence to authorities.

There are several means of curbing the spread of these invaders, and some have even taken to eating invasive crayfish as a means of population control.

While crayfish are considered a delicacy in many parts of the world, I'm not going to recommend you eat anything caught in the Humber River.

Lead photo by

Geza Farkas/Shutterstock

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