The Status and Distribution of Maryland Crayfishes

Over 45 years have passed since the last examination of Maryland's crayfish fauna. We compiled crayfish records from over 1400 sites sampled since 1989 and present an update on the current status and distribution of Maryland's 9 native species. Five non-native species have become established in Maryland waters and represent the greatest threat to Maryland's native species. Orconectes virilis (Virile Crayfish), the most widespread invasive species in the state, has been primarily introduced by anglers as bait and has rapidly expanded its distribution in central Maryland. The spread of this species has been followed by concurrent declines in native species including O. limosus (Spinycheek Crayfish) and O. obscurus (Allegheny Crayfish). Non-native Cambarus thomai (Little Brown Mudbug), O. rusticus (Rusty Crayfish), Procambarus clarkii (Red Swamp Crawfish), and P. zonangulus (Southern White River Crawfish) are now established in Maryland as a result of aquaculture and bait introductions. Recent taxonomic revisions have also added C. carinirostris (Rock Crawfish) to the list of species present in the state.