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Rusty crayfish

Quick facts

Rusty crayfish is a regulated invasive speciesRegulated Invasive Species (MN DNR) are legal to buy, sell, transport, and possess, but may not be introduced into a free-living state, such as released into public waters.

  • Rusty crayfish feeding habits threaten native plant beds and native fish eggs and young fish.
  • They can drive native crayfish out, making them susceptible to predators.

Rusty crayfish should be reported. Learn how to report invasive species in Minnesota.

Rusty crayfish. Image: Bob McNamara.

How to identify rusty crayfish

  • Rusty crayfish (Orconectes rusticus (syn. Faxonius rusticus)) has a light to dark brown body. Rusty, red-colored spots are present on either side of carapace.
  • Spot size and darkness is highly variable across individuals.
  • Has larger, more robust claws than native crayfish species.
  • Claws have dark black bands on the tips.
  • When closed, the claws have an oval gap in the middle.
Rusty crayfish oval gap in the middle of closed claw.
Rusty crayfish oval gap in the middle of closed claw

Life cycle

  • Mature rusty crayfish mate in late summer, early fall, or early spring.
  • Rusty crayfish females can lay between 80 and 575 eggs.
  • Females carry sperm transferred from male crayfish until eggs are ready for fertilization. It is possible for a single crayfish to start a new population if transferred to a new water body.
  • Eggs hatch in three to six weeks depending on water temperature.
  • Juveniles stay with the female for several weeks after hatching and reach full maturity the following year upon completion of about 8 to 10 molt cycles.
  • Rusty crayfish typically live 3–4 years.

Reviewed in 2019

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