Shelter occupancy by mixed-species pairs of native signal crayfish and non-native red swamp crayfish held in enclosures

Abstract

Sheltering ability does not appear to confer an advantage to non-native red swamp crayfish (Procambarus clarkil) in a small, western Washington lake where the invader outnumbers the native signal crayfish (Pacifastacus leniusculus.) When paired with similar-sized non-native P. clarkii, P. leniusculus was adept at monopolizing limited artificial shelter inside enclosures placed on the bottom of Pine Lake. In these contests, the dominant crayfish or winner was typically the one with longer chelae, or, in the case of P. clarkii, the one that was sexually mature. Female crayfishes of both species also were adept at monopolizing the artificial shelter. Furthermore, irrespective of species and sex, when paired with smaller heterospecifics, large crayfish readily monopolized the artificial shelter. These results suggest that additional mechanisms besides shelter competition are contributing to the possible displacement of P. leniusculus in Pine Lake. © 2009, Copyright Taylor & Francis Group, LLC.