2009 NORTHEASTERN NATURALIST 16(4):655–663 The Invasion of Procambarus clarkii (Decapoda: Cambaridae) into Maryland Streams Following its Introduction in Outdoor Aquaculture Ponds Jay V. Kilian1,*, Jason Frentress2, Ronald J. Klauda1, Andrew J. Becker1, and Scott A. Stranko1 Abstract - We provide locality data for stream populations of Procambarus clarkii (Red Swamp Crawfish) in Maryland. This non-native species is now established in 14 watersheds in the Coastal Plain, including all watersheds where it was historically raised in aquaculture ponds. Our surveys indicate that the introduction of Red Swamp Crawfish in Maryland has largely resulted from aquaculture, although the aquarium, biological supply, and live-bait industries are other potential vectors. The effects of Red Swamp Crawfish on the composition and diversity of stream fauna and flora in Maryland are unknown. The establishment of this species may have negative effects on native crayfishes, especially the congeneric P. acutus (White River Crawfish). These locality records provide baseline information for future monitoring of this non-native species and assessment of its effects on Maryland’s stream ecosystems and native crayfishes. Introduction Non-native crayfish introductions are considered the largest threat to North America’s crayfish fauna, the second-most imperiled fauna on the continent (Lodge et al. 2000a; Stein and Flack 1997; Taylor et al. 1996, 2007). The documentation of non-native crayfish introductions into new areas is necessary to assess the effects of these species on ecosystem function and native crayfish diversity (Cooper et al. 1998). Procambarus clarkii Girard (Red Swamp Crawfish), native to the southcentral United States and northern Mexico, is the most widely cultured and distributed crayfish in the world (Huner 2002) and has been introduced on all continents except Australia and Antarctica, usually with negative consequences (Hobbs et al. 1989). The first known introduction of Red Swamp Crawfish in Maryland occurred in 1963 at the Patuxent National Wildlife Refuge in Laurel in the Patuxent River basin. Several individual crayfish were introduced to shallow water impoundments as a potential food source for wading birds (Matthew Perry, USGS-Patuxent Wildlife Research Center, Laurel, MD, 2006 pers. comm.). Red Swamp Crawfish have also been introduced into outdoor ponds for the purposes of commercial aquaculture in Maryland. The Worcester 1Maryland Department of Natural Resources, Monitoring and Non-tidal Assessment, 580 Taylor Avenue, Annapolis, MD 21401. 2Oregon State University, Water Resources Science, 2075 Cordley Hall, Corvallis, OR 97331. *Corresponding author - jkilian@dnr.state.md.us. 656 Northeastern Naturalist Vol. 16, No. 4 County Soil Conservation District initiated a crayfish aquaculture trial in 1981, during which seed-stock purchased from Louisiana was used to stock impoundments in the Pocomoke River (Pattys Branch) and Nanticoke River (Rewastico Creek) basins to examine the feasibility of crayfish culture in Maryland (Bruce Nichols, Hebron, MD, pers. comm.). The results of this trial indicated that sustained, profitable crayfish production could occur in Maryland. In 1983, the Mid-Atlantic Crawfish Association was established. With 250 members at its peak, this group of farmers and landowners promoted crayfish aquaculture in the Mid- Atlantic region. The original Louisiana seed-stock was used to stock Red Swamp Crawfish in outdoor ponds for commercial aquaculture on the Delmarva Peninsula and in Southern Maryland (Bruce Nichols, pers. comm.). It was also used to stock culture ponds on the University of Maryland Eastern Shore campus for research (David O' Neill, Community College of Baltimore County, Baltimore, MD, pers. comm.). Most of the stocking of Red Swamp Crawfish promoted by the Mid-Atlantic Crawfish Association occurred prior to the establishment of aquaculture permit regulations by the Maryland Department of Natural Resources (MDNR) in 1990. Many locations where Red Swamp Crawfish were introduced were not formally documented and are unknown. There are seven known locations where Red Swamp Crawfish were historically introduced into outdoor ponds for culture in Maryland; commercial aquaculture is still conducted at two of these locations. In 2006, we examined the role of aquaculture as a source of introduction of Red Swamp Crawfish in Maryland streams. We conducted targeted surveys in streams adjacent to all seven aquaculture facilities. We also collected data on stream crayfishes at sites sampled as part of the Maryland Department of Natural Resources’ Maryland Biological Stream Survey (MBSS). These surveys documented populations of this non-native species in streams and rivers on Maryland’s coastal plain. The goals of this report are to 1) compile all known records of Red Swamp Crawfish to document its current distribution in Maryland, and 2) to discuss the likely vectors responsible for the introduction of this species. Documentation of these records will prove useful for examining changes in the distribution of this species over time. Methods Locations of aquaculture ponds where Red Swamp Crawfish were cultured were provided by MDNR Fisheries Service personnel, crayfish farmers, and researchers (Richard Bohn, MDNR Fisheries Service, Annapolis, MD, pers. comm.; Bruce Nichols, pers. comm.; David O' Neill, pers. comm.; Matthew Perry, pers. comm.). We sampled 16 sites in non-tidal streams adjacent to seven aquaculture ponds. Crayfishes were collected using dip-nets. Crayfish burrows in stream banks were excavated by hand. Dip-netting was supplemented with backpack electrofishing at sites where dip-netting was not 2009 J.V. Kilian, J. Frentress, R.J. Klauda, A.J. Becker, and S.A. Stranko 657 considered sufficient to provide a representative sample of crayfish species present. All crayfishes captured were identified to species. One record of Red Swamp Crawfish from a stream adjacent to an aquaculture pond in the Nanticoke River was provided by David O' Neill of the Community College of Baltimore County. Crayfish sampling was also conducted at 172 sites as part of the annual Maryland Biological Stream Survey. Backpack electroshockers (Smith-Root Model 12; Haltech Model HT-2000) were used to sample non-tidal stream sites. Non-wadeable rivers and freshwater impoundments were sampled using a jonboat outfitted with a Smith-Root Model KVA electrofisher. Boat electroshocking was supplemented by seining (1.5 m x 3.0 m, 0.3-cm mesh; 1.8 m x 7.6 m, 0.6-cm mesh) in shallow, heavily vegetated shoreline habitats at three sites sampled in the tidal Potomac River. All crayfishes collected at each MBSS site were field-identified to species. All Red Swamp Crawfish specimens collected in 2006 were preserved in alcohol and are currently stored at the MDNR in Annapolis, MD. Results Non-native Red Swamp Crawfish were collected at 35 sites in 14 watersheds (Maryland 8-digit HUC) in the coastal plain on the western shore of Chesapeake Bay and on the Delmarva Peninsula (Fig. 1, Appendix 1). Populations were documented in streams adjacent to all known ponds where Figure 1. Stream sites where Red Swamp Crawfish were collected. 658 Northeastern Naturalist Vol. 16, No. 4 Red Swamp Crawfish were once cultured and in portions of the Patuxent, Potomac, and Chester rivers (Fig. 2). Discussion The most important vectors responsible for the introduction of non-native crayfishes throughout North America are the aquaculture, aquarium, biological supply, and live-bait industries (Lodge et al. 2000b). The results of this study indicate that the introduction of Red Swamp Crawfish in Maryland has largely resulted from aquaculture. This species is now established in streams adjacent to all aquaculture ponds where it was introduced for commercial culture or for aquaculture-related research. The vector or vectors responsible for the introductions of Red Swamp Crawfish in the Potomac and Chester Rivers are unknown. Although no aquaculture facilities in the Potomac River or Chester River basins are or were registered with the MDNR Fisheries Service, these introductions may have resulted from undocumented aquaculture in these areas. It is also likely that these populations are the result of the inadvertent introduction of Red Swamp Crawfish as bait, or intentional release by aquarium hobbyists. The population documented in the Western Branch watershed of the Patuxent River was approximately 70 river km from the original introduction site in the Patuxent National Wildlife Refuge. This population could have Figure 2. Maryland watersheds (8-digit HUC) with established stream populations of Procambarus clarkii (Red Swamp Crawfish) and locations of aquaculture ponds where this species was originally introduced. 2009 J.V. Kilian, J. Frentress, R.J. Klauda, A.J. Becker, and S.A. Stranko 659 originated from the downstream dispersal of Red Swamp Crawfish within the Patuxent River or from a separate introduction event. The effects of Red Swamp Crawfish on ecosystem function and the composition and diversity of aquatic fauna and flora in Maryland are unknown. Many transplants of this species throughout the world have resulted in crop damage, damage to levees and dams as a result of burrowing activity, or changes to regional flora and fauna (Hobbs et al. 1989, Holdich 1988, Lowery and Mendes 1977). The establishment of this species in Maryland waters may have negative effects on native crayfishes, especially the congeneric P. acutus Girard (White River Crawfish). Red Swamp Crawfish, the more aggressive of the two species, may likely out-compete White River Crawfish for shelter or other limited resources, and ultimately displace the native species (Gherardi and Daniels 2004) as appears to have occurred in portions of North Carolina (Cooper and Armstrong 2007). Native displacement by non-native crayfishes is a phenomenon that has been documented extensively (Capelli 1982, Capelli and Munjal 1982, Holdich 1988, Lodge et al. 2000a, Schwartz et al. 1963), prompting many states to establish regulations on the import, culture, and sale of these potentially damaging species (Lodge et al. 2000b). In Maryland, an aquatic nuisance species list drafted in 2006 seeks to limit the import and transport of several problematic invasive species (COMAR 2006). Non-native crayfishes on this list include Red Swamp Crawfish, Orconectes virilis Hagen (Virile Crayfish), and O. rusticus Girard (Rusty Crayfish). The establishment of stream populations of Red Swamp Crawfish as a result of the aquaculture of this species in outdoor ponds has major management implications and should be considered in decisions involving the culture of this and other non-native species in other states. Efforts to eradicate Red Swamp Crawfish have been extensive and costly in other areas of the country (Barbaresi et al. 2004, Hobbs et al. 1989), and future attempts will likely prove futile in Maryland and could harm native species. Pesticide application is likely to harm non-target species (Bills and Marking 1988, Olden et al. 2006), and toxicants may be ineffective on Red Swamp Crawfish individuals in protected burrows. Other approaches such as trapping would be labor-intensive and may also be ineffective. Red Swamp Crawfish is likely to spread into new watersheds in Maryland’s coastal plain. Changes in the physical and chemical characteristics of streams that occur above the Fall Line may prevent it from invading the piedmont of Maryland. Its spread on the coastal plain will likely be limited by saltwater. The new records presented here improve our understanding of the distribution of this non-native species and establish a baseline for future crayfish surveys in Maryland. Since the culture of Red Swamp Crawfish generally results in the establishment of breeding populations in surrounding water bodies (Hobbs et al. 1989, Lodge et al. 2000a), it is likely that additional extant populations of Red Swamp Crawfish exist in Maryland watersheds 660 Northeastern Naturalist Vol. 16, No. 4 beyond those that are reported here. Undocumented stocking of Red Swamp Crawfish mentioned above is likely to have occurred in watersheds not surveyed during 2006. Additional surveys are necessary to determine the distributional limits of Red Swamp Crawfish throughout Maryland. Also, the effects of this species on native crayfishes and other aquatic fauna and flora are unknown and require further research and additional monitoring. Acknowledgments We thank David O’Neill for providing his records and history of Red Swamp Crawfish culture at UMES and John Cooper for providing information on Maryland crayfishes and information on Red Swamp Crawfish in North Carolina. We thank Arnold Norden for sharing his knowledge of Maryland crayfishes. We are also grateful to Bruce Nichols, Matthew Perry, Ralph Andrews, and Eric May for providing invaluable information on the history of crayfish aquaculture in Maryland. We also thank Rebecca Chalmers, Karl Hellman, Richard Raesly, Gerald Mack, Joseph Smith, Virginia Eaton, Rachel Gauza, Matthew Kline, Matthew Sell, Aaron Gates, Ryan Utz, Ann Roseberry-Lincoln, Mark Southerland, Chris Millard, and Dan Boward for their efforts in crayfish data collection. This study was funded in part by State Wildlife Grant funds provided to the state wildlife agencies by US Congress, and administered through the Maryland Department of Natural Resources’ Natural Heritage Program. Literature Cited Barbaresi, S., G. Santini, E. Tricarico, and F. Gherardi. 2004. Ranging behavior of the invasive crayfish, Procambarus clarkii (Girard). Journal of Natural History 38:2821–2832. Bills, T.D., and L.L. Marking. 1988. Control of nuisance populations of crayfish with traps and toxicants. Progressive Fish Culturist 50:103–106. Capelli, G.M. 1982. Displacement of Northern Wisconsin crayfish by Orconectes rusticus (Girard). Limnology and Oceanography 27:741–745. Capelli, G.M., and B.L. Munjal. 1982. Aggressive interactions and resource competition in relation to species displacement among crayfish of the genus Orconectes. Journal of Crustacean Biology 2:486–492. Code of Maryland (COMAR). 2006. 08.02.19.00. Maryland Department of Natural Resources. Annapolis, MD. Cooper, J.E., and S.A. Armstrong. 2007. Locality records and other data for invasive crayfishes (Decapoda: Cambaridae) in North Carolina. Journal of the North Carolina Academy of Science 123:1–13. Cooper, J.E., A.L. Braswell, and C. McGrath. 1998. Noteworthy distributional records for crayfishes (Decapoda: Cambaridae) in North Carolina. Journal of the Elisha Mitchell Scientific Society 114:1–10. Gherardi, F., and W.H. Daniels. 2004. 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Fisheries 25 (89):21–23. Lowery, R.S., and A.J. Mendes. 1977. Procambarus clarkii in Lake Naivasha, Kenya, and its effects on established and potential fisheries. Aquaculture 11:111–121. Olden, J.D., J.M. McCarthy, J.T. Maxted, W.W. Fetzer, and M.J. Vander Zanden 2006. The rapid spread of Rusty Crayfish (Orconectes rusticus) with observations on native crayfish declines in Wisconsin (USA) over the past 130 years. Biological Invasions 8:1621–1628. Schwartz, F.J., R. Rubelmann, and J. Allison. 1963. Ecological population expansion of the introduced crayfish, Orconectes virilis. Ohio Journal of Science 63(6):266. Stein, B.A., and S.R. Flack. 1997. 1997 species report card: The state of US plants and animals. The Nature Conservancy, Arlington, VA. Taylor, C.A., M.L. Warren, Jr., J.F. Fitzpatrick, Jr., H.H. Hobbs III, R.F. Jezerinac, W.L. Pflieger, and H.W. Robison. 1996. Conservation status of crayfishes of the United States and Canada. Fisheries 21:25–38. Taylor, C.A., G.A. Schuster, J.E. Cooper, R.J. DiStefano, A.G. Eversole, P. Hamr, H.H. Hobbs III, H.W. Robison, C.E. Skelton, and R.F. Thoma. 2007. A reassessment of the conservation status of crayfishes of the United States and Canada after 10+ years of increased awareness. Fisheries 32:372–388. 662 Northeastern Naturalist Vol. 16, No. 4 Appendix 1. Collection records of Procambarus clarkii (Red Swamp Crawfish) summarized by river basin and watershed (Maryland 8-digit Hydrologic Unit). Site River basin Watershed (8-digit) Location Latitude (NAD83) Longitude (NAD83) Collection date 1 Patuxent Patuxent River upper Goose Pond outlet stream 39º01'46" 76º47' 55" 26 July 2006 2 Patuxent Western Branch Tributary to Collington Branch 38º56'09" 76º45'17" 15 July 2006 3 Patuxent Western Branch Tributary to Collington Branch 38º56'10" 76º45'17" 15 July 2006 4 Patuxent Western Branch Tributary to Lottsford Branch 38º58'11" 76º48'29" 15 July 2006 5 Potomac Nanjemoy Creek Mill Run 38º29'01" 77º05'09" 18 July 2006 6 Potomac Potomac Middle Tidal Tributary to Mallows Bay 38º28'15" 77º15'31" 10 May 2006 7 Potomac Potomac Middle Tidal Tributary to Mallows Bay 38º28'30" 77º15'26" 09 June 2006 8 Potomac Potomac Middle Tidal Tributary to Mallows Bay 38º28'14" 77º15'34" 12 June 2006 9 Potomac Potomac Middle Tidal Tributary to Mallows Bay 38º28'27" 77º15'45" 25 June 2006 10 Potomac Potomac Middle Tidal Tributary to Mallows Bay 38º28'29" 77º15'22" 25 June 2006 11 Potomac Potomac Middle Tidal Potomac River 38º28'15" 77º15'57" 25 July 2006 12 Potomac Potomac Middle Tidal Tributary to Wades Bay 38º26'30" 77º15'23" 08 June 2006 13 Potomac Potomac Middle Tidal Tributary to Wades Bay 38º26'11" 77º15'09" 08 June 2006 14 Potomac Potomac Middle Tidal Tributary to Wades Bay 38º25'48" 77º15'03" 07 June 2006 15 Potomac Mattawoman Creek Mattawoman Creek 38º35'47" 77º08'14" 22 Aug 2006 16 Potomac Mattawoman Creek Mattawoman Creek 38º35'26" 77º07'17" 22 Aug 2006 17 Potomac Potomac Upper Tidal Bryan Point 38º41'46" 77º03'59" 21 Aug 2006 18 Chester Corsica River Three Bridges Branch 39º03'34" 76º00'43" 18 July 2006 19 Chester Corsica River Three Bridges Branch 39º03'36" 76º00'39" 18 July 2006 20 Chester Corsica River Three Bridges Branch 39º03'07" 76º02'24" 26 Sept 2006 21 Chester Corsica River Three Bridges Branch 39º03'16" 76º03'02" 31 July 2006 22 Chester Corsica River Alder Branch 39º04'18" 76º04'00" 24 July 2006 23 Chester Corsica River Gravel Run 39º02'56" 76º03'47" 31 July 2006 24 Chester Lower Chester River Swan Creek 39º11'38" 76º13'07" 26 July 2006 25 Nanticoke Manokin Branch Manokin Branch 38º12'57" 75º39'55" 03 Aug 2006 2009 J.V. Kilian, J. Frentress, R.J. Klauda, A.J. Becker, and S.A. Stranko 663 Site River basin Watershed (8-digit) Location Latitude (NAD83) Longitude (NAD83) Collection date 26 Nanticoke Fishing Bay Roadside ditch at Egypt Road 38º28'33" 76º06'04" 21 June 2006 27 Nanticoke Fishing Bay Blackwater National Wildlife Refuge 38º26'51" 76º05'21" 21 June 2006 28 Nanticoke Fishing Bay Blackwater National Wildlife Refuge 38º26'51" 76º05'11" 21 June 2006 29 Nanticoke Fishing Bay Tributary to Little Blackwater River 38º32'34" 76º05'12" 21 June 2006 30 Nanticoke Nanticoke River Rewastico Creek 38º24'39" 75º45'16" 1989* 31 Pocomoke Lower Pocomoke River Pattys Branch 38º10'18" 75º22'19" 29 Aug 2006 32 Pocomoke Lower Pocomoke River Bachelors Branch 38º05'50" 75º29'22" 26 Aug 2006 33 Pocomoke Upper Pocomoke River Old Mill Branch 38º16'32" 75º18'21" 23 Oct 2006 34 Atlantic Chincoteague Bay Tributary to Pawpaw Creek 38º09'44" 75º17'55" 26 June 2006 35 Atlantic Chincoteague Bay Tributary to Scarboro Creek 38º09'32" 75º18'10" 26 June 2006 *Record provided by David O'Neill, Community College of Baltimore County, MD.