Rusty Crayfish

  • Rusty Crayfish

    (Orconectes rusticus)

    Unlike many harmful invasive species in Ontario, the Rusty Crayfish does not come from overseas, but rather from our neighbors to the south. The Rusty Crayfish is native to the Ohio River basin in the United States. This species was likely introduced to Ontario by anglers from other areas discarding the crayfish they were using as bait. Another possibility is that the Rusty Crayfish may also have been introduced by people who acquired them as pets or through the scientific supply trade.

    Rusty Crayfish are commonly found in lakes, rivers, ponds, and streams with clay, silt, and gravel bottoms that contain rocks, logs, or other debris the crayfish can hide under. They eat large quantities of vegetation and their large size and aggressive nature helps protect them from being eaten by native fish. A single female with 200 fertilized eggs can start a new population in an area not previously colonized by the Rusty Crayfish. There is currently no practical way to remove this invasive species once it has been established.


    The Rusty Crayfish was first recorded in Ontario in the early 1960’s from the Kawartha Lakes region. They can now be found throughout much of south-central and southeastern Ontario, including Manitoulin Island, the Magnetawan River, the Kawartha Lakes Basin, the Ottawa River Basin, and in northwestern Ontario.


    U.S. Geological Survey Archive, U.S. Geological Survey,

    U.S. Geological Survey Archive, U.S. Geological Survey,

    U.S. Geological Survey Archive, U.S. Geological Survey,

    U.S. Geological Survey Archive, U.S. Geological Survey,

  • Identification

    • Rusty Crayfish are large, with adults reaching 7.5-13 centimetres from rostrum (the part of the shell in front the eyes) to the tail.
    • Rusty patches on each side of the shell.
    • Grayish-green to reddish-brown claws with black bands near the tips.
    • Claws have an oval gap when closed.
    • The rostrum is smooth, pinched, and distinctly concave.
    • There are a number of Ontario crayfish that are similar in appearance to the Rusty Crayfish including the native northern Clearwater crayfish (O. propinquus), the native virile crayfish (O. virilis), and the introduced obscure crayfish (O. obscurus). None of these species have a pinched rostrum, black claw bands, or rusty patches on the shell.


    • Rusty Crayfish compete with native species of crayfish for food and habitat, often causing the decline or extirpation of native crayfish.
    • Since these invaders are larger and more aggressive than native crayfish, they are better able to avoid being eaten by predators, increasing the likelihood that native species will be preyed upon.
    • Rusty Crayfish destroy suitable spawning and nursery habitat for native fish by consuming large quantities of vegetation.
    • Female crayfish carry fertilized eggs under their tail, an ability that has allowed the Rusty Crayfish to spread very rapidly.

    Help Stop the Spread

    • Learn how to properly identify Rusty Crayfish and how to prevent accidentally spreading this invasive species.
    • Familiarize yourself with native species of crayfish so you can better spot invaders.
    • If you are using crayfish as bait, you may only use them in the waterbody where they were caught. The maximum number of live crayfish you can have in your possession is at one time is 36.
    • If you have any information about the illegal importation, distribution or sale of rusty crayfish, report it immediately to the Ministry of Natural Resources TIPS line at 1-877-TIPS-MNR (847-7667) toll-free any time, or contact your local Ministry of Natural Resources office ( during regular business hours. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477).
    Ontario Invaders Species Account PDF
    U.S. Geological Survey Archive, U.S. Geological Survey,

    U.S. Geological Survey Archive, U.S. Geological Survey,