Plants and Animals

Cambarus robustus Big water crayfish

species photo
Peter Badra
species photo
Peter Badra
species photo
Kelley Smith

Key Characteristics

The big water crayfish is a relatively large crayfish with a carapace length often greater than 5 cm. Color is usually olive green to dark brown. They have a spoon shaped rostrum without marginal spines. The areola is moderately wide. The chela (claws) are large and stout with two rows of rounded tubercles on the mesial margin of the palm. The gonopods on form I males have two short, sharply angled (90 degrees), sickle shaped elements at the terminal end.

Status and Rank

US Status: No Status/Not Listed
State Status: SC - Special Concern (rare or uncertain; not legally protected)
Global Rank: G5 - Secure
State Rank: S2? - Imperiled (inexact or uncertain)


CountyNumber of OccurrencesYear Last Observed
Alcona 5 2015
Arenac 4 2015
Clare 2 1968
Crawford 1 2015
Eaton 1 1965
Gladwin 3 2015
Hillsdale 3 2015
Ionia 1 1967
Iosco 4 2015
Kalamazoo 1 1988
Kalkaska 1 2015
Kent 1 2014
Lapeer 3 2015
Lenawee 4 2015
Macomb 3 2015
Midland 1 2015
Montcalm 2 2015
Montmorency 2 1968
Oakland 5 2018
Ogemaw 2 2015
Oscoda 1 2015
Presque Isle 1 1968
Roscommon 2 2015
Sanilac 1 2015
Washtenaw 3 2015

Information is summarized from MNFI's database of rare species and community occurrences. Data may not reflect true distribution since much of the state has not been thoroughly surveyed.


Big water crayfish are most often found in medium to large, fast flowing rivers and streams with rocky substrates. They also can occasionally be found in lakes and ponds with rocky substrates. Big water crayfish are commonly found under large flat rocks, as they do not normally use burrows except to escape freezing temperatures or desiccation during hot weather. They can move over dry land short distances if required and tolerate a wide range of water temperature and pH.

Natural Community Types

  • Great lake, littoral, benthic
  • Inland lake, littoral, benthic
  • Mainstem stream (3rd-4th order), pool
  • Mainstem stream (3rd-4th order), run
  • Mainstem stream (3rd-4th order), riffle
  • River (5th-6th order), pool
  • River (5th-6th order), run
  • River (5th-6th order), riffle

For each species, lists of natural communities were derived from review of the nearly 6,500 element occurrences in the MNFI database, in addition to herbarium label data for some taxa. In most cases, at least one specimen record exists for each listed natural community. For certain taxa, especially poorly collected or extirpated species of prairie and savanna habitats, natural community lists were derived from inferences from collection sites and habitat preferences in immediately adjacent states (particularly Indiana and Illinois). Natural communities are not listed for those species documented only from altered or ruderal habitats in Michigan, especially for taxa that occur in a variety of habitats outside of the state.

Natural communities are not listed in order of frequency of occurrence, but are rather derived from the full set of natural communities, organized by Ecological Group. In many cases, the general habitat descriptions should provide greater clarity and direction to the surveyor. In future versions of the Rare Species Explorer, we hope to incorporate natural community fidelity ranks for each taxon.

Management Recommendations

The invasive red swamp crayfish (Procambarus clarkii) and rusty crayfish (Faxonius rusticus) can displace native crayfish species. Minimizing the spread of these harmful species can increase the viability of big water crayfish populations as well as benefit other components of the river ecosystem. Vectors for introduction of red swamp crayfish and rusty crayfish include live food markets, bait shops, and improper handling after classroom use. Anthropogenic changes to river and lake ecosystems such as shoreline hardening, dredging, and point source discharges should be avoided when possible or minimized. Contamination from heavy metals and the introduction of non-native predatory fish can also negatively impact big water crayfish populations.

Active Period

Active from first week of March to fourth week of October

Survey Methods

Big water crayfish can be collected with seine nets, dip nets, minnow traps, and by hand.  Baited minnow traps set overnight can be very effective in collecting large numbers of crayfish.


Survey References

  • Creaser, E.P. 1930. The Michigan decapod crustaceans. Michigan Academy of Science Arts and Letters 13: 257-276.
  • Lippson, R.L. 1975. “The Distribution of the Crayfish of Michigan with Aspects of Their Life Cycle and Physiology.” PhD dissertation, Michigan State University.
  • Taylor, C.A., G.A. Schuster, and D.B. Wylie. 2015. Field Guide to Crayfishes of the Midwest. Manual 15. Illinois Natural History Survey, Champaign. x+145pp.

Technical References

  • Crandall, K.A., and S. De Grave. 2017. An updated classification of the freshwater crayfishes (Decapoda: Astacidea) of the world, with a complete species list. Journal of Crustacean Biology 37: 615-653.
  • Edwards, B.A., et al. 2009. Multispecies crayfish declines in lakes: implications for species distributions and richness. Journal of the North American Benthological Society 28(3)
  • Guiasu, R.C. “Cambarus.” In, Biology of Freshwater Crayfish, edited by David M. Holdich, Blackwell Science Ltd, 2002, pp. 609-631.
  • Smith, K., B. Roth, M. Jones, D. Hayes, S. Herbst, and N. Popoff. 2019. Changes in the distribution of Michigan crayfishes and the influence of invasive rusty crayfish (Faxonius rusticus) on native crayfish substrate associations. Biological Invasions 21: 637–656.
  • Smith, K., B. Roth, S. Herbst, R. Thoma, N. Popoff, D. Hayes, and M. Jones. 2018. Assessment of invasion risks for red swamp crayfish (Procambarus clarkii) in Michigan, USA. Management of Biological Invasions 9: 405–415.
  • 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: 372-389.