Daily Invader

Chesapeake Bay Crayfish

Virile Crayfish (Orconectes virilis)


Virile Crayfish (Orconectes virilis) was introduced into Chesapeake Bay the late 1950s.


The Virile Crayfish is native to the Mississippi and Great Lakes basins and was introduced into the Chesapeake and other Atlantic drainages in the late 1950s (first record 1957). This small crayfish is widely sold as bait and frequently released by fishermen. It is now widespread in the Chesapeake Bay watershed. Its spread was accompanied by the displacement of two native crayfish, the Spiny-cheek Crayfish (Orconectes limosus) and the Appalachian Brook Crayfish (Cambarus bartonii), in Maryland and West Virginia streams. The displacement of these species is believed to be due to the  wider environmental tolerances, larger size, and more aggressive behavior of the Virile Crayfish. Complete Record 


Rusty Crayfish (Orconectes rusticus)


Rusty Crayfish may make great fishing bait, but as an introduced species they could have large negative impacts on your fishing hole.



The Rusty Crayfish is native to the Ohio drainage but introduced to at least 15 states, mainly in the Northeast and Midwest, and Ontario and New Brunswick, Canada. Its range is rapidly expanding due to a mixture of natural dispersal, aggressive displacement of other species, and human introductions. Crayfish have been widely introduced with discarded bait, but probably also through the released from aquarium and laboratory animals. A crayfish was collected in the Susquehanna River in 1976 near Harrisburg and reported to occur down to Conowingo Dam, MD, however, there were no reports of the crayfish in Maryland until 2007 when it was seen in Conowingo Creek about 10 km above Conowingo Dam. That same year it was found in the Monocacy River, a Potomac tributary in Frederick County Maryland and was expected to spread into other parts of the Potomac drainage. Further spread of this species is of concern because it could have wide-ranging ecological implications and economic impacts, particularly on fisheries. Complete Record
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