Description: The Northern crayfish (Orconectes virilis) is a small, lobster-like crustacean that inhabits freshwater areas throughout the United States. Its coloration is typically muddy green to reddish-brown for all individuals, regardless of age, size and gender. The pincers are green to greenish blue with orange tips and may be studded with white knobs in adults.1
Habitat: The Northern crayfish prefers permanent, well-oxygenated
ponds, lakes, rivers and streams with substrates of silt to cobble.
It may occur in water as shallow as a few inches to as deep as
100 feet and will tolerate water temperatures ranging from 1-32_C
Total Range: Historically, the Northern crayfish had an expansive range from eastern Alberta, Canada, east to the southern boundary of Quebec, south to include New York, Ohio, Kentucky, Arkansas and Texas, west to include Colorado and Utah and finally back north through Wyoming and Montana. Popularity of this species as bait and as an aquatic weed controller has greatly increased its range into 16 more states including Arizona, which is the only state with no native crayfish species.1
Reproduction: In Arizona, mating occurs during late summer to early autumn, although it may occur during the winter to a limited extent.1 The female carries the eggs beneath her abdomen until they hatch, several days to weeks after mating has occurred. Juveniles leave for independent life shortly after hatching.2
Diet: O. virilis is an opportunistic omnivore, which means they eat just about anything they can put their claws around, including aquatic plants, larval fish, snakes, turtles, insects and other invertebrates.3
Threat to Native Species and/or Environments: Since Arizona has few natural agents to control them, crayfish populations have exploded. Their appetite for larval fish, plants and insects can seriously hurt both natural aquatic ecosystems and man made fisheries.3 Crayfish have been implicated in a number of native species declines in Arizona, including lowland leopard frogs and mud turtles in Sycamore Creek (near Sunflower) and the Little Colorado spinedace (Lepidomeda vittata). There may also be a concern for the protection and conservation of other endangered Arizona fishes such as the spikedace (Meda fulgida) and the desert pupfish (Cyprinodon macularius) which may directly compete with the northern crayfish for territory.1
Mechanisms by which crayfish are introduced into the wild include escape or release from bait buckets and discard by aquarium enthusiasts. Chemical use and traps are two methods by which crayfish can be controlled in an area, but these are costly and populations can quickly regain their numbers once the control activity is ceased. The best way to control crayfish is to prevent their introduction in the first place.
Northern crayfish in Pima County: Northern crayfish exist in Rose Canyon Lake located in the Santa Catalina Mountains and may exist in other lakes or stock ponds within Pima County. Preventing their introduction into our aquatic ecosystems will help protect some of our endangered native species, including the Chiricahua leopard frog and the Gila topminnow.
1 Inman, T. C. 1999. An introduction to Arizona's crayfish with an emphasis on Orconectes Virilis. The Arizona Riparian Council newsletter. Vol. 12, No. 3, pp. 5-7.
2 New Mexico Department of Game and Fish et al. 1998. BISON-M: New Mexico Species List/Species
3 Miera, V. May-June 1999. Simple Introductions-Major Repercussions: The story of bullfrogs and crayfish in Arizona. Wildlife Views. pp. 25-27.