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​Rusty Crayfish

Rusty Crayfish (Orconectes rusticus) is of one of Ontario's most unwanted invasive species. 

This crayfish species is native to the Ohio River system in the United States, and is believed to have been introduced into Ontario either by use as bait or dumping from an aquarium.


  • Rusty crayfish tend to be larger than native species; the length of their claws are relatively long.

  • This species will usually have two rusty patches on either side of their shell, but not always.

  • They have thin black bands on the tips of their claws.

  • When the claws are closed, there is an oval gap between them. 

  • The rostrum (extension between their eyes) is distinctively concave.

Where are Rusty Crayfish in our watershed?

Rusty crayfish have been reported from a number of watercourses within the watershed including: Masters Creek (headwater tributary of the Nottawasaga River), Boyne River, Lamont Creek, Egbert Creek, Black Ash Creek, and Besley Drain (tributary to the Boyne River).

Why are they of concern?

Rusty crayfish can feed at a rate of twice that of a native crayfish species. This can reduce aquatic plant diversity as well as, fish and benthic populations since rusty crayfish also feed on fish eggs and invertebrates that live on the bottom of rivers and lakes. This decrease in food availability can cause local extinctions of native crayfish species! As well, a female can hold up to 200 fertilized eggs, allowing a single rusty crayfish to quickly establish a population in a new area.

How to Control the Spread

  • Remember to drain water from your motor, live well, and bilge whenever leaving a water body.

  • Clean all aquatic equipment by either warm water, water pressure washer, or leave in the sun for 5 days.

Early Detection is Key

Early detection and rapid response is essential for the control and/or eradication of invasive species in an area. If you spot a Rusty Crayfish, please report the sighting to EDDmapS Ontario

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