FRESHWATER CRAYFISH | 2011| vol. 18| issue 1 | Research Article
 
doi: 10.5869/fc.2011.v18.45 |  View Table of Contents

Full Citation: 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.



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

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.

Keywords: Austropotamobius pallipes; invasive; Pacifastacus leniusculus; trapping; Thelohania contejeani

Article Language: English

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