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rusty crayfish

Orconectes rusticus

What do they look like?

Rusty crayfish have robust claws unlike other members of the genus Orconectes. They are dark reddish, brown and have dark, rusty spots on each side of the carapace at the base of the cephalothorax. (Gunderson, 1995)

  • Range length
    10.2 (high) cm
    4.02 (high) in

Where do they live?

The rusty crayfish is an invader species in northern lakes and streams of the Great Lakes region. Native to the Ohio River Basin and Ohio, Kentucky, Tennessee, Indiana, and Illinois, they have expanded their range to Michigan, Minnesota, Wisconsin, Missouri, Iowa, Pennsylvania, New York, New Jersey, New England (except Rhode Island), and parts of Ontario, Canada. (Gunderson, 1995)

What kind of habitat do they need?

This crayfish inhabits permanent streams, lakes and ponds that have rocky substrate and logs or debris as cover. They will inhabit pools of still water or fast-flowing streams. (Crandall and Fetzner, 2003; Gunderson, 1995)

  • These animals are found in the following types of habitat
  • freshwater

How do they grow?

Depending on the water temperature, rusty crayfish eggs hatch in 3 to 6 weeks. Young crayfish will undergo 3 to 4 molts while attached to the mother's swimmerets and remain with the mother for several weeks. Once the young have left, they undergo 8 to 10 molts before becoming mature. Maturity usually occurs the following year. Maturity is considered to be at a length of 4.4 cm. After mature, adult males will molt twice annually, and adult females will molt once annually. (Gunderson, 1995)

How do they reproduce?

Rusty crayfish mate in late summer, early fall or early spring. Males transfer sperm to the females, but external fertilization does not occur until the water temperature increases. The expelled eggs are fertilized by the sperm and are attached to the swimmerets underneath the crayfish's abdomen with white patches. These white patches are called glair, and and the eggs adhere to this mucus-like substance. From 80 to 575 eggs are laid. (Gunderson, 1995)

How long do they live?

The rusty crayfish typically lives to be 3 to 4 years old. (Gunderson, 1995)

How do they behave?

The rusty crayfish does not excavate deep burrows. They may dig shallow pockets under rocks or debris. The rusty crayfish are aggressive and will force native crayfish from daytime hiding areas. When threatened, they assume a "claws-up" posture to prevent fish predation.

In addition, their aggression occurs with discrete postures that lead to fighting. When one rusty crayfish comes in contact with another, the meral spread is the first threat display posture to occur. Next, wrestling occurs, but claw use is restrained as the rusty crayfish partake in this phase of an aggressive encounter over a period of time. Finally, unrestrained use of the claws occurs during a brief period of time. (Gunderson, 1995; Huber, 1999)

How do they communicate with each other?

During encounters, rusty crayfish respond to each other depending on the presence of urine. The stronger the odor, which serves as a chemical cue, the shorter in duration and the lesser the aggression during a first agonistic interaction. In addition, urine serves as a recognition cue in that a rusty crayfish that won a first fight over an opponent will recognize that opponent and display dominance during a second aggressive encounter, but the second encounter will be shorter in duration. (Zulandt-Schneider, et al., 2001)

What do they eat?

The rusty crayfish is a voracious feeder because of its high metabolic rate. Juvenilles feed on benthic invertebrates and fish eggs.

Foods eaten include: aquatic plants, snails, clams, leeches, aquatic insects, other aquatic crustaceans and fish eggs. (Gunderson, 1995)

What eats them and how do they avoid being eaten?

Rusty crayfish will used their hooked claws in a defensive posture to protect themselves from fish predators. (Gunderson, 1995)

  • Known Predators
    • fish

What roles do they have in the ecosystem?

Because of its aggressive nature, the rusty crayfish is replacing native Great Lakes crayfish such as Orconectes propinquus. Many organisms live on the exoskeleton and other organisms are internally parasitic in crayfish. (Crocker and Barr, 1968; Gunderson, 1995)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host
  • ostracods
  • branchiobdellids

Do they cause problems?

These crayfish have displaced native species. They may affect the fisheries industry since they feed heavily on aquatic plants that are important habitat for other invertebrates (foodstuffs for fish), shelter for fish, nesting substrate for fish, and aid in erosion control. (Gunderson, 1995)

How do they interact with us?

Among agencies concerned about ecosystem management in the Great Lakes region, there is a debate about using rusty crayfish to control Eurasian watermilfoil, an invasive aquatic plant. (Gunderson, 1995)

Are they endangered?

This species is not afforded any special conservation status.

Some more information...

Initially, the rusty crayfish was introduced to the northern part of the Great Lakes region by fishermen who used them as bait. As the population of rusty crayfish increased, they were harvested for use as fish bait and sold to biological supply companies. This provided impetus to breeding rusty crayfish, and subsequently, releasing them, intentionally or otherwise, into non-native waters.

There is also concern about hybridization of this species with the native northern clearwater crayfish, Orconectes propinquus.

Another common name for crayfish is crawfish or crawdad. (Gunderson, 1995; Lodge and Feder, 2001)


Renee Sherman Mulcrone (editor).

Janice Pappas (author), University of Michigan-Ann Arbor.


Crandall, K., J. Fetzner. 2003. "Orconectes (Procericambarus) rusticus" (On-line). The Crayfish Home Page. Accessed October 02, 2003 at

Crocker, D., D. Barr. 1968. Handbook of the Crayfishes of Ontario. Life Sciences Miscellaneous Publications, Royal Ontario Museum. University of Toronto Press: Toronto.

Gunderson, J. 1995. "Minnesota Sea Grant/rusty crayfish factsheet" (On-line). Accessed January 23, 2002 at

Huber, R. 1999. "Lab Exercise 3-Agonistic Behavior in Crayfish, Animal Behavior-Biology 420/543, Bowling Green State University, Fall 2001" (On-line). Accessed January 24, 2002 at

Lodge, D., J. Feder. 2001. "Illinois-Indiana Sea Grant College Program" (On-line). Dispersal of Exotic Species in the Great Lakes:Crayfish as a Model System for Benthic Species. Accessed July 19, 2004 at

Zulandt-Schneider, R., R. Huber, P. Moore. 2001. Individual and status recognition in the crayfish, Orconectes rusticus: the effects of urine release on fight dynamics. Behaviour, 138: 137-153.

University of Michigan Museum of ZoologyNational Science Foundation

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Pappas, J. 2002. "Orconectes rusticus" (On-line), Animal Diversity Web. Accessed April 17, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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