Shelter Competition Between Two Invasive Crayfish Species: A Laboratory Study

Abstract

Alien crayfishes represent a common threat to aquatic ecosystems. Their spread in Europe is leading to more frequent contacts between different invasive species populations. Shelter can be an important factor in the resulting interactions. A laboratory experiment was designed to analyse the competition for shelter in similarly sized males of two species that show an invasive behaviour in Spain, Pacifastacus leniusculus and Procambarus clarkii.We carried out 24 heterospecific, six-hour trials, with 30 min behavioural observations per hour. Most often, red swamp crayfish were both the first (70.8%) and the long-term winner (62.5%). Usually, the long-term winner was the first winner. Whenever shelter was occupied, a passive behaviour by unsheltered individuals was more frequent in signal crayfish than in red swamp crayfish. When both were unsheltered, signal crayfish displayed more often a passive behaviour.Although the observed behaviour might be explained as the result of dominance by the red swamp crayfish over the signal crayfish, shelter availability and class, as well as different growth patterns and population size structures, could change the intensity and the outcome of the encounters in the wild, where signal crayfish usually reach larger sizes than red swamp crayfish.Key-words: competition, shelter, crayfish, Pacifastacus leniusculus, Procambarus clarkii, invasive species. COMPÉTITION POUR LES REFUGES EN CONDITIONS DE LABORATOIRE ENTRE DEUX ESPÈCES INVASIVES D'ÉCREVISSES RÉSUMÉLes écrevisses exotiques représentent une menace pour les écosystèmes aquatiques. Leur dispersion généralisée en Europe a pour conséquence une augmentation de la fréquence de contact entre différentes populations d'espèces invasives. La disponibilité des refuges est un facteur important du résultat de ces interactions. Une expérimentation en laboratoire a été conçue pour analyser la compétition pour les refuges entre mâles de Nous avons mis en place 24 lots interspécifiques de 6 heures, avec des périodes d'observation de 30 minutes par heure. Dans 70,8 % des cas, les écrevisses de Louisiane ont été les premières à occuper les abris, et aussi les vainqueurs sur le long terme dans 62,5 % des cas. En général, le premier arrivé a gardé sa place au long-terme. Lorsque l'abri était occupé, les écrevisses signal ont montré plus souvent un comportement passif que les écrevisses de Louisiane. Lorsque des spécimens des deux espèces étaient sans abri, les écrevisses signal ont fait preuve plus souvent d'un comportement passif.Bien que les comportements observés puissent être interprétés comme un avantage des écrevisses de Louisiane sur les écrevisses signal, la disponibilité et le type des refuges ainsi que des différences dans la structure et dans la croissance des populations peuvent modifier l'intensité et l'issue des rencontres en milieux naturels, où les écrevisses signal atteignent généralement une taille supérieure à celle des écrevisses de Louisiane.

Dispersal and coexistence of two non-native crayfish species (Pacifastacus leniusculusandProcambarus clarkii) in NE Portugal over a 10-year period

“…In River Maçãs, the temperature tolerance limits of both species are never exceeded but minimum temperatures and possibly other environmental dimensions related to the upriver conditions affect P. clarkii more than P. leniusculus and seem the most probable cause for the observed differences of CPUE and species proportions. Laboratory studies showed P. clarkii wins agonistic interactions (Figler et al, 1995(Figler et al, , 1999Gherardi et al, 1999;Gherardi and Daniels, 2004;Alonso and Martínez, 2006) which strongly support the hypothesis that P. leniusculus dominance in most river sectors and the upper limit of P. clarkii distribution is mostly the result of environmental conditions. The persistence of the crayfish coexistence remains to be seen and as both species are generalists and potential invaders, coexistence is expected to persist where both species face some degree of environmental stress, i.e., no dominance and displacement will happen because neither of them lives under optimal conditions.…”

“…Policar and Kozák, 2005;Gallagher et al, 2006), traps are still the most frequently employed method of capturing crayfish Momot and Gowing, 1972;Byrne et al, 1999;Demers and Reynolds, 2002;Flotemersch and Jackson, 2003;Lyons and Kelly-Quinn, 2003;Martínez et al, 2003;Yamamoto, 2010). Previous studies have shown variable levels of aggression among different crayfish species (Figler et al, 1995(Figler et al, , 1999Gherardi et al, 1999;Gherardi and Daniels, 2004;Tierney et al, 2000;Alonso and Martínez, 2006;Luan, 2009) and in situations of coexistence, traps may underestimate the abundance of the less aggressive species. Electrofishing is possibly a more effective technique to detect and sample crayfish (e.g.…”

Competitive interactions between co-occurring invaders: identifying asymmetries between two invasive crayfish species

“…Vorburger and Ribi 1999), to account for the effect of body size and mass pairs were matched so that differences between pair members did not exceed 10% for all three compared measurements (W, CL and RCL), as in other dyadic studies of crayfish interactions (e.g. Söderbäck 1991;Schroeder and Huber 2001;Alonso and Martinez 2006;Fero et al 2007 etc.). Before the start of each laboratory trial, crayfish were kept in total isolation for 24 h during which each individual was kept in separate plastic tank with aerated water.…”

Niche differentiation among invasive crayfish and their impacts on ecosystem structure and functioning

“…Lodge et al ., ; Nyström, Brönmark & Granéli, ). Invasive species of crayfish regularly outcompete and replace native crayfish (Hill & Lodge, ; Alonso & Martínez, ; Dunn et al ., ; Haddaway et al ., ), but interactions among invasive crayfish are rarely examined despite the increasing likelihood of them occurring in sympatry. While competition has resulted in serial replacement of invasive crayfish in some instances (Hill & Lodge, ), coexisting populations are known (Nakata et al ., ; Bernardo et al ., ), but their combined interactive effect on the ecosystem is unknown.…”