The Nottawasaga Valley Conservation Authority

Rusty Crayfish

What is 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.

Rusty crayfish

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 with warm water, a pressure washer, or leave in the sun for 5 days.

If you use crayfish as live bait, remember that it is only legal to use them where you catch them. It is illegal to transport any crayfish species, dead or alive, or land.  NEVER move crayfish from where you catch them.

Never release pets or dump the contents of an aquarium into the wild.

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.

More information

Invasive species on private property

NVCA does not offer a service to remove invasive species on private property.  If you are looking for tips on dealing with invasive species on your property, see the links above, or Ontario’s Invading Species Awareness Program.

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