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Invasion progress of the signal crayfish (Pacifastacus leniusculus (Dana)) and displacement of the native white-clawed crayfish (Austropotamobius pallipes (Lereboullet)) in the River Wharfe, UK
Imhoff EM, Mortimer RJG, Christmas M and Dunn AM 
Published Online: 12/31/2011
Abstract
Invasive signal crayfish are a major threat to the endangered native white-clawed crayfish in Britain. The River Wharfe in Yorkshire is the site of a signal crayfish invasion that has been progressing since the late 1980s. A recent discovery in this river was signal crayfish infected with Thelohania contejeani, a microsporidian parasite which normally infects white-clawed crayfish and causes porcelain disease. During 2007 and 2009 we delineated the ongoing invasion by trapping and hand sampling, and compared sex ratios and sizes seasonally and spatially. We screened crayfish of both species for T. contejeani using PCR to determine parasite prevalence. The invasion in the river has progressed at an overall downstream rate of 1.7 km yr-1 and an overall upstream rate of 0.5 km yr-1. A reduction in native crayfish populations has occurred in the downstream reach of the river even in locations not immediately threatened by signal crayfish. Sex ratios of captured signal crayfish varied seasonally and spatially throughout the invasion zone. Thelohania contejeani was found in both crayfish species at similar overall prevalence (12%, signal; 14%, white-clawed), and there is concern that signal crayfish may serve as reservoir hosts for the parasite where they co-occur with white-clawed crayfish.
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Imhoff EM, Mortimer RJG, Christmas M and Dunn AM. (2011). Invasion progress of the signal crayfish (Pacifastacus leniusculus (Dana)) and displacement of the native white-clawed crayfish (Austropotamobius pallipes (Lereboullet)) in the River Wharfe, UK. Freshwater Crayfish 18(1):45-53. doi: 10.5869/fc.2011.v18.45
Author Information
Emily M. Imhoff,* , Missouri Department of Conservation, 1110 South College Avenue, Columbia , MO, USA65201. E-mail: eimhoff@gmail.com
Robert J. Mortimer, School of Earth and Environment, University of Leeds, Faculty of Environment, Leeds, , UKLS2 9JT. E-mail: r.j.g.mortimer@leeds.ac.uk
Martin Christmas, Phoenix House, Environment Agency, Global Avenue, Leeds, , UKLS11 8PG. E-mail: martin.christmas@environment-agency.gov.uk
Alison M. Dunn, Faculty of Biological Sciences, University of Leeds, IICB, Leeds, , UKLS2 9JT. E-mail: a.dunn@leeds.ac.uk
Corresponding Author indicated by an *.
Publication History
Manuscript Submitted: 12/23/2010
Manuscript Accepted: 10/9/2011
Published Online: 12/31/2011
Published in Print: 12/31/2011
Funding Information
No specific funding statement is available for this article.