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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.

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

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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