Common name: Big Water Crayfish

Synonyms and Other Names: Cambarus robustus is a species complex. A recently published study describes three new species within this complex. More information about the species complex can be found in the study, Loughman et al. (2017). As it is unclear which species within the species complex the introduced specimens are, all introduced specimens are treated as C. robustus.

Taxonomy: available through www.itis.gov

Identification: The overall body color is greenish-brown. This species possesses large, strong chelae and a long, narrow rostrum (Guarino et al. 2012; Massachusetts Division of Fisheries and Wildlife 2015). The corners of the rostrum are rounded and the chelae have two rows of bumps on the margin of the palm (Guarino et al. 2012). C. robustus are a large species of crayfish with carapace lengths of more than 5 cm (2 inches) (Guarino et al. 2012).

Size: Up to 6 cm carapace length (Hamr and Berrill 1985).

Native Range: The range extends from the eastern Midwest of the U.S. to the Northeast, from Michigan to New York (west of the Hudson River) and south to Tennessee (Hobbs, 1989).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology:     Cambarus robustus are a large crayfish that prefer fast flowing water and rocky substrate (Guiasu, 2002), although they may also be found in larger precambrian shield lakes (Hamr and Berrill, 1984). Some individuals have a carapace length of more than 5 cm (Guarino et al., 2012).
    Originally, C. robustus were thought to lack a well defined mating season in contrast to crayfish of the Faxonius genus which have relatively synchronous life cycles (Crocker and Barr, 1968). However, a study by Hamr and Berrill (1985) described a more well defined life history; females reach sexual maturity at 40 mm carapace length (cpl) while males mature at 39 mm cpl at approximately 2 years of age. Mating occurs in summer with the majority of females in berry by July. Males typically molt following breeding in September or early October. Males do not usually survive to spawn more than once (Hamr and Berrill, 1985).
    Small juvenile C. robustus are typically filter feeders when they become free living; adults have a broader diet consisting of vegetation, aquatic insects, and smaller crayfish (Hamr, 1998).

Means of Introduction: Probable bait release (Lodge et al. 2000).

Status: Established in Connecticut and New York; the status is unknown in Vermont (Guarino et al. 2012).

Impact of Introduction: Unknown. However, Guiasu and Dunham (1999) found that, in its native range, C. robustus exhibited dominant aggressive behavior towards Cambarus bartonii bartonii during direct encounters.

Remarks: While not normally a burrower, Berrill and Chenoweth (1982) found that C. robustus has the ability to burrow. Cambarus robustus is known to survive in acidic lakes (Taylor et al. 1995). Cambarus robustus may be confused with C. b. bartonii, which has a shorter rostrum and a smaller maximum size (Massachusetts Division of Fisheries and Wildlife 2015).

References: (click for full references)

Beauchene, M. 2011. Crayfish distribution project. Connecticut Department of Energy and Environmental Protection Bureau of Water Protection and Land Reuse, Hartford, Connecticut. http://www.ct.gov/deep/lib/deep/water/water_quality_management/monitoringpubs/2011_crayfishdist.pdf. Accessed: 22 June 2017.

Berrill, M., and B. Chenoweth. 1982. The burrowing ability of nonburrowing crayfish. The American Midland Naturalist 108(1):199-201.

Guarino, J., C. Gastador, and E. Miller. 2012. Field guide to the crayfish of the White River watershed, east-central Vermont. White River Partnership and Verdana Ventures, LLC, Randolph, Vermont. http://whiteriverpartnership.org/wp-content/uploads/2014/04/Field-Guide-to-the-Crayfish-of-the-White-River-Watershed.pdf. Accessed: 22 June 2017.

Guiasu, R., and D.W. Dunham. 1999. Aggressive interactions between the crayfishes Cambarus bartonii bartonii and C. robustus (Decapoda: Cambaridae): interspecific and intraspecific contests. Journal of Crustacean Biology 19(1):131-146.

Hamr, P., and M. Berrill. 1985. The life histories of north-temperate populations of the crayfish Cambarus robustus and Cambarus bartoni. Canadian Journal of Zoology 63:2313-2322.

Hobbs, H.H., Jr. 1989. An illustrated checklist of the American crayfishes (Decapoda: Astacidae, Cambaridae, and Parastacidae). Smithsonian Contributions to Zoology 480:1-236.

Lodge, D.M, C.A. Taylor, D.M. Holdich, and J. Skurdal. 2000. Nonindigenous crayfishes threaten North American freshwater biodiversity: lessons from Europe. Fisheries 25(8):7-19.

Loughman, Z.J., and T.P. Simon. 2011. Zoogeography, taxonomy, and conservation of West Virginia's Ohio River floodplain crayfishes (Decapoda, Cambaridae). ZooKeys 74:1-78.

Loughman, Z.J., S.M. Henkanaththegedara, J.W. Fetzner, and R.F. Thoma. 2017. A case of Appalachian endemism: Revision of the Cambarus robustus complex (Decapoda: Cambaridae) in the Kentucky and Licking River basins of Kentucky, USA, with the description of three new species. Zootaxa 4269(4):460-494. https://doi.org/10.11646/zootaxa.4269.4.4.

Massachusetts Division of Fisheries and Wildlife. 2015. Appalachian Brook Crayfish fact sheet. Natural Heritage and Endangered Species Program, Westborough, MA.

Taylor, R.M., G.D. Watson and M. A. Alikha. 1995. Comparative sub-lethal and lethal acute toxicity of copper to the freshwater crayfish, Cambarus robustus (Cambaridae, Decapoda, Crustacea) from an acidic metal-contaminated lake and a circumneutral uncontaminated stream. Water Research 29(2):401-408.

Other Resources:
US Fish and Wildlife Service fact sheet

Great Lakes Waterlife

Author: Durland Donahou, A., Boucher, N., Elgin, A.

Peer Review Date: 6/22/2017

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.