Taxonomic name: Orconectes virilis (Hagen, 1870)
Synonyms:
Common names: northern crayfish (English), virile crayfish (English)
Organism type: crustacean Orconectes virilis (northern crayfish) is closely related to the lobster. Orconectes virilis can be found in lakes, rivers, streams, marshes and ponds, and requires shelter in the form of rocks, logs or thick vegetation in which to hide from predators. Its spread is fostered by its popularity as a food and as baitfish. Orconectes virilis is also spread via the aquarium trade as pets or as food for predaceous fishes. Description
According to Collicut (1998), O. virilis grows to a length of about 10-12cm, not including the 2 pairs of long antennae or the large chelipeds (the large pincer bearing legs) that extend forward. Chelipeds often have a bluish tint, particularly in males, which have larger chelipeds and pincers than females. The head and thorax are covered by a shell-like carapace that is usually brownish to rusty red in colour. Similar Species
Astacidea
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Occurs in:
lakes, water courses, wetlands Habitat description
According to Collicut (1998), O. virilis can be found in lakes, rivers, streams, marshes, and ponds. They are found in permanent bodies of water deep enough not to freeze solid or experience low oxygen levels. O. virilis requires shelter in the form of rocks, logs, or thick vegetation in which to hide from predators during daylight hours. General impacts
According to Godfrey (2002), O. virilis is of serious concern because its burrows in ditches and levee banks may disrupt irrigation networks. Burrows near head gates and weir boxes often make it impossible to maintain an acceptable water head. O. virilis' burrowing and swimming activities may also muddy the water, reducing photosynthesis in submerged plants. Harvested grain may be contaminated as soil is forced out of O. virilis burrows, suspended as the field is drained, and picked up by harvesting machinery. O. virilis eats rice seeds and seedlings, and their digging uproots seedlings. Floating leaf parts may indicate feeding by tadpole shrimp, but crushed, macerated, submerged rice seed is unique to crayfish. Extensive damage of this sort has not been a frequent or widespread problem and is mainly associated with fields that have been in rice for several consecutive seasons. Uses
Crayfishes are popular food items in the United States and increasingly in Europe as well (Collicut, UNDATED). According to Huner (1997), crayfishes have been most commonly used as food and fish bait but are also commercially exploited in the pet trade as pets and food for predaceous pet fishes. Geographical range
Native range: O. virilis has a North American native range from Alberta to Quebec, Canada (PCAO, UNDATED), and in the United States it is native from Montana and Utah to Arkansas, north to the Great Lakes, and east to New York. It is introduced in the United States in parts of the Southwest, Southeast, the mid-Atlantic, and the Northeast (NAS, UNDATED). It is also introduced in Chihuahua, Mexico (Fullerton, 2002). Introduction pathways to new locations
Aquaculture: Crayfishes are harvested from natural waters by commercial fishers and anglers or cultivated in small earthen ponds (Huner, 1997),
Live food trade: According to Huner (1997), crayfishes have been most commonly used as food and fish bait but are also commercially exploited in the pet trade as pets and food for predaceous pet fishes.
Pet/aquarium trade: According to Huner (1997), crayfishes have been most commonly used as food and fish bait but are also commercially exploited in the pet trade as pets and food for predaceous pet fishes. Management information
Preventative measures: To minimise impacts to irrigation systems, Godfrey (2002) suggests checking the system for crayfish damage all season long and repair damage to levees, paddy weir boxes and major irrigation structures as soon as possible to prevent accidental draining of the field. If damage from O. virilis is evident in rice fields and plant stand drops below acceptable levels (25 to 30 seeds or seedlings per square foot) during the first two weeks after flooding, the field can by drained temporarily to drive the crayfish into their burrows until the rice seedlings are well established. This does not kill the crayfish, however, damage will be minimised as once the seedlings are older they are not as susceptible to injury. A decision to drain must consider negative aspects, such as fertiliser loss, encouragement of weeds or interruption of weed control procedures, interruption of pesticide drainage requirements and the economics of irrigation. Nutrition
According to Collicut (1998), O. virilis eats some aquatic plants as well as invertebrates, such as snails and insects; it also eats tadpoles and small fish. They are probably best described as opportunistic omnivores consuming whatever they can catch. While they can catch some quick moving prey like tadpoles or fish, they probably obtain most of their food by scavenging dead animals. Reproduction
Collicut (1998) states that Orconectes virilis can mate in autumn or in spring. However, the eggs are not fertilized and laid until spring. Females can store sperm from a fall mating and protect their eggs by carrying them under their tales. Eggs are attached to swimmerets in a large ball resembling a raspberry. The eggs hatch one to two months after they are laid. Young hatchlings look like miniature adults and can probably grow to about 2-3cm long by the fall. Lifecycle stages
Collicut (1998) notes that O. virilis has a short lifespan. Males usually die after mating when they are about 2 years old. The females die after their young hatch, also at about 2 years of age. O. virilis occasionally lives longer, but it's thought that none survive beyond their 4th spring. Reviewed by: Dr. Brian Hazlett. Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor. USA
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
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Last Modified: Monday, January 24, 2005
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