First Record of the Invasive Orconectes rusticus (Rusty
Crayfish) from the Potomac River, Maryland
Jay V. Kilian1.* and Patrick Ciccotto2
Abstract - We report the first record of invasive Orconectes rusticus (Rusty Crayfish) in the Potomac
River, MD. Four specimens were collected in June 2010 in the Potomac River downstream
from the confluence of Antietam Creek near Sharpsburg, MD. Subsequent surveys in the Potomac
River mainstem and three other tributaries from Brunswick to Hancock, MD indicate that this invasive
species is not yet widespread in the river. Further spread of Rusty Crayfish in the Potomac
River may displace congeneric species including two natives, Orconectes obscurus (Allegheny
Crayfish) and Orconectes limosus (Spinycheek Crayfish), and the non-native Orconectes virilis
(Virile Crayfish) in Maryland, Virginia, and West Virginia.
Orconectes rusticus (Girard) (Rusty Crayfish), a species native to portions of the Ohio
River basin, has been widely introduced outside of its native range primarily through its
use as bait (Taylor et al. 2007). Now established in at least 18 states as well as Canada,
Rusty Crayfish has gained notoriety as an aggressive invasive species (Hobbs et al 1989,
Lodge et al. 2000, Olden et al. 2009). Rusty Crayfish has caused local displacement of native
crayfishes (Capelli 1982, Lodge et al. 1986) and hybridized with congeneric species
(Capelli and Capelli 1980, Perry et al. 2001, Smith 1981). Impacts of Rusty Crayfish on
aquatic vegetation, benthic macroinvertebrates, snails, and fishes have also been documented
(Hobbs et al. 1989, Houghton et al. 1998, Olsen et al. 1991, Wilson et al. 2004).
On 9 June 2010, we conducted surveys to document the distributions of crayfishes in
large (4th order and higher) streams in the Valley and Ridge physiographic province, a
portion of Maryland that has not been surveyed for crayfishes in nearly 50 years (Kilian
et al. 2010). We surveyed a total of 10 sites in the Potomac River and in four tributaries,
including Licking, Conococheague, Little Conococheague, and Antietam creeks.
During this effort, we documented the first record of the invasive Rusty Crayfish in the
Potomac River (Fig. 1). Using a 3-m × 1-m kick seine, we collected four individuals
(3 Form II males, 1 female) in a gravelly riffle among emergent vegetation on the Maryland
shoreline approximately 100 m downstream of the confluence of Antietam Creek
south of Sharpsburg, MD (39.41708 N, 77.74670 W). The four specimens collected from
this location ranged in size from 26 to 31mm (mean = 26.8 mm carapace length). These
specimens are currently stored at the Maryland Department of Natural Resources in Annapolis,
MD. Rusty Crayfish was also collected in high abundance at three sites in the
lower reaches of Antietam Creek (Fig. 1).
Prior to this survey, the known distribution of Rusty Crayfish in the Maryland portion
of the Potomac River basin included the upper Monocacy River near Emmitsburg, where
it was discovered in 2007 (Kilian et al. 2010) and Antietam Creek north of Sharpsburg,
where it was discovered in 2008 (Ellen Friedman and Neal Dziepak, MDNR Resource
Assessment Service, Annapolis, MD, 2010 pers. comm.). Our findings extend the known
range of Rusty Crayfish in the basin to include the lower reaches of Antietam Creek south
of Sharpsburg and adjacent portions of the mainstem Potomac River. Its invasion of the
1Maryland Department of Natural Resources, Monitoring and Non-tidal Assessment, 580 Taylor
Avenue, Annapolis, MD 21401. 2University of Maryland Baltimore County, Department of Biological
Sciences, 1000 Hilltop Circle, Baltimore, MD 21250. *Corresponding author - jkilian@dnr.
Notes of the Southeastern Nat u ral ist, Issue 10/3, 2011
554 Southeastern Naturalist Vol. 10, No.3
Potomac River likely occurred through its downstream dispersal from Antietam Creek,
where it has been established for at least several years. We did not collect Rusty Crayfish
at other sites sampled in the Potomac River or in the lower reaches of Licking, Conococheague,
and Little Conococheague creeks, suggesting that this invasive species is not yet
widely dispersed in the river (Fig. 1).
The possession of Rusty Crayfish is prohibited in Maryland (Code of Maryland
Regulations 08.02.19.04), and the use and possession of all species of live crayfish is
currently banned in the portion of the Potomac River basin where Rusty Crayfish is now
established. These regulations are intended to slow the spread of this invasive species via
Figure 1. Distribution of Rusty Crayfish in the upper Potomac River based on 10 sites sampled in
2011 Southeastern Naturalist Notes 555
bait-bucket transfer. However, the Potomac River is now a conduit through which Rusty
Crayfish can spread naturally into Virginia, West Virginia, and other Maryland tributaries
where it may compete with and displace congeneric species, including the native
Orconectes obscurus (Hagen) (Allegheny Crayfish) and Orconectes limosus (Rafinesque)
(Spinycheek Crayfish), and the non-native Orconectes virilis (Hagen) (Virile Crayfish).
The impacts of Rusty Crayfish in the Potomac River may reach beyond congeneric species.
As a top predator and consumer of a wide variety of prey, Rusty Crayfish has the
potential to alter the entire trophic web (Charlebois and Lamberti 1996, Hobbs et al.
1989). It has reduced the diversity and abundance of benthic macroinvertebrates (Charlebois
and Lamberti 1996, Houghton et al. 1998, McCarthy et al. 2006, Olsen et al. 1991)
and aquatic vegetation (Olsen et al. 1991, Peters et al. 2008) in other invaded areas. Impacts
on populations of snails (Wilson et al. 2004), unionid mussels (Klocker and Strayer
2004), and fishes (Hobbs et al. 1989) are also possible. Further surveys are necessary
to monitor the dispersal of this invasive species and to document its effects on crayfish
populations and other biological communities in the Potomac River.
Acknowledgments. We thank John Schuster and Adam Eshleman for assistance with
field sampling. We also thank Andrew Landsman and Scott Bell of the National Park
Service, Scott Stranko, Ronald Klauda, and the MDNR Invasive Species Matrix Team for
their support and guidance. Special thanks to Brian Watson and two anonymous reviewers
for their editorial review and helpful comments that improved this manuscript. This
study was funded in part by State Wildlife Grant funds provided to state wildlife agencies
by US Congress through the US Fish and Wildlife Service, and administered through the
Maryland Department of Natural Resources’ Natural Heritage Program.
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