Invasive Species Council of Manitoba

Rusty Crayfish(Orconectes rusticus)

History: Rusty Crayfish is an aggressive species, originating in the Ohio River Basin, USA, which began to spread into the northern Great lakes regions, including Minnesota, Wisconsin and Ontario in the 1960s. They are often spread by anglers who use them as bait.

Physical Description

General: Rusty Crayfish have large claws with black bands near the tips and are larger in size than our native Crayfish.There are dark, rusty spots on each side of their brown body (as though you picked up the Crayfish with paint on your forefinger and thumb). The spots may not always be present or well developed on Rusty Crayfish from some waters.

Threat

The major threat is the reduction of aquatic plantbeds and the species that live in these environments. It is said that the damage the Rusty Crayfish does to the aquatic system is the equivalent of clear cutting forests. Rusty Crayfish, especially juveniles, feed heavily on aquatic plants, small fish and water insects, often twice as much as a native Crayfish. This puts strain on the food sources for young fish and other invertebrates.

Distribution

Rusty Crayfish are a new invader to Manitoba, being first spotted in Falcon Lake in 2007. Since then, it has been illegal to possess any Crayfish in Manitoba to prevent the spread of rusty crayfish between bodies of water from bait bucket transfers.

Rusty Crayfish

Top: Rusty Crayfish (note nail head on the dock for scale). Bottom: Slightly different colour variation.

Photos: D. Watkinson, Fisheries and Oceans Canada (Freshwater Institute Winnipeg) [B] J. Gunderson, MN Sea Grant

For more information or to report a sighting call 1-87-STOP-AIS-0 or 1(877) 867-2470.

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