Rusty crayfish

Orconectes rusticus
Conservation status
Least Concern  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Malacostraca
Order:	Decapoda
Infraorder:	Astacidea
Superfamily:	Astacoidea
Family:	Cambaridae
Genus:	Orconectes
Species:	O. rusticus
Binomial name
Orconectes rusticus (Girard, 1852)

The rusty crayfish, Orconectes rusticus, is a large, aggressive species of freshwater crayfish which is native to the U.S. states of Indiana, Kentucky, Ohio, and Tennessee. Its range is rapidly expanding in North America, displacing native crayfishes in the process: it is known to have reached New England, Ontario, Illinois, Wisconsin, Michigan, Minnesota, Iowa, Missouri, New Jersey, New York, Pennsylvania, Maryland, and even Manitoba. The rusty crayfish was first captured in Illinois in 1973, and has been collected at over 20 locations in the northern portion of the state. In 2005, O. rusticus was found for the first time west of the Continental Divide, in the John Day River, Oregon, which drains into the Columbia River.

Rusty crayfish are considered a threat to many ecosystems. Once introduced, rusty crayfish proliferate quickly, often displacing native crayfish through hybridization and/or superior predatory defense. Predator defense in crayfish is primarily restricted to displays with their chelae, raising them in a threatening manner. Because rusty crayfish generally have larger claws and are more aggressive than congeneric species, several studies have noted that fish predators actually avoid consuming rusty crayfish in favor of more docile or smaller species that flee when threatened.

Ecosystem impacts of rusty crayfish are often profound. Rusty crayfish remove aquatic plants, either through consumption or by clipping the plant at its base. Researchers have theorized that this ability to decimate aquatic plants actually leads to further population expansion by eliminating key habitat for the juveniles of sunfish species that act as predators on juvenile crayfish.

Diet: Submerged plants, detritus, other crayfish, juvenile fish, sunfish, fish eggs, macrophytes.

Submissive fish species such as the sunfish can not defend their nests from rusty invasions and so lose their future offspring, greatly reducing the fish population. Other species of fish such as bass are more aggressive and will eat any invaders that wander too near to their nests, or if the intruder is too big to eat, it will simply pick it up and move it out of its territory.

External links

• www.invadingspecies.com Partnership between the Ontario Ministry of Natural Resources and the Ontario Federation of Anglers and Hunters
• http://www.crayfishontario.ca/
• http://www.issg.org/database/species/ecology.asp?si=217
• http://animaldiversity.ummz.umich.edu/site/accounts/information/Orconectes_rusticus.html
• Species Profile- Rusty Crayfish (Orconectes rusticus), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Rusty Crayfish.

Further reading

• Alan P. Covich‌, Margaret A. Palmer‌, Todd A. Crowl (1999). "The Role of Benthic Invertebrate Species in Freshwater Ecosystems: Zoobenthic species influence energy flows and nutrient cycling". BioScience. 49 (2): 119–127. doi:10.1525/bisi.1999.49.2.119.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Julian D. Olden, Julia M. McCarthy, Jeffrey T. Maxted, William W. Fetzer & M. Jake Vander Zanden (2006). "The rapid spread of rusty crayfish (Orconectes rusticus) with observations on native crayfish declines in Wisconsin (U.S.A.) over the past 130 years". Biological Invasions. 8 (8): 1621–1628. doi:10.1007/s10530-005-7854-2.{{cite journal}}: CS1 maint: multiple names: authors list (link)</ref>