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Freshwater Crayfish 20(1): 41-60 (2014)


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Factors Associated with the Distributions and Densities of Three Native and One Non-Native Crayfish in Streams of Maryland, USA

Kilian JV and Ciccotto PJ  e-mail link

Published Online: 12/31/2014


Crayfish are among the most imperiled faunal groups, yet data on habitat associations and environmental stressors for conservation efforts are lacking for most species. We used an existing stream survey dataset generated by the Maryland Department of Natural Resources from 2007 to 2009 to quantify associations between eight environmental variables and three native (Cambarus bartonii bartonii, Orconectes limosus, and Procambarus acutus) and one non-native (O. virilis) crayfish. We accounted for spatial autocorrelation within the data set and observed significant associations between crayfish densities and environmental variables at both the reach and watershed scales. The density of C. b. bartonii was significantly correlated with stream gradient, and this species was also associated with higher forested land cover and cooler stream temperatures. Density of O. limosus was positively associated with upstream catchment area suggesting an affinity for larger streams. Procambarus acutus density was positively correlated with total nitrogen concentrations and negatively associated with the quality of riffle and run habitats. The density of the non-native O. virilis was positively associated with urban land cover. Counter to what has been reported from other states, syntopic occurrence of native species was rare in Maryland. Cambarus b. bartonii was syntopic with O. limosus at only 5% of sites where the ranges of both species overlapped. Similarly, syntopic occurrence of P. acutus and O. limosus was only 10%. The range of O. limosus in the Piedmont region of Maryland has declined precipitously from historical levels. This decline appears to be more related to the concurrent spread of O. virilis (i.e., species replacement) than to other potential explanations (i.e., urbanization). In contrast, the spread of O. virilis has not resulted in widespread displacement or replacement of C. b. bartonii or P. acutus. Our analyses suggest that the three native species are not particularly sensitive to urbanization, pH, or nitrogen eutrophication. Although there are myriad potential stressors to Maryland crayfish, the results of our study indicate that the most important of these is the continued introduction and spread of non-native crayfish. Immediate conservation should focus on preventing the further spread of O. virilis and other non-native crayfish in the state.

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Kilian JV and Ciccotto PJ. (2014). Factors Associated with the Distributions and Densities of Three Native and One Non-Native Crayfish in Streams of Maryland, USA. Freshwater Crayfish 20(1):41-60. doi: 10.5869/fc.2014.v20-1.41



Author Information

Jay  Kilian,* Resource Assessment Service, Maryland Department of Natural Resources, 580 Taylor Avenue C-2, Annapolis, Maryland, USA21401. E-mail:

Patrick  Ciccotto, Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland, United States21250. E-mail:

Corresponding Author indicated by an *.


Publication History

   Manuscript Submitted: 11/14/2014

   Manuscript Accepted: 12/23/2014

   Published Online: 12/31/2014

   Published in Print: 12/31/2014



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No specific funding statement is available for this article.






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