The Dispersion of the Aphanomyces Astaci-Carrier Pacifastacus Leniusculus by Humans Represents the Main Cause of Disappearance of the Indigenous Crayfish Austropotamobius Pallipes in Navarra

Abstract

The tendency of population decline of the indigenous crayfish, Austropotamobius pallipes, in Navarra was reduced by the implementation of a plan of restoration in 1996. Recently, a new drop in population numbers has been noticed. In 2004, an extensive survey was carried out to study the reasons for this decline. The results showed that indigenous crayfish had disappeared from 37 out of 73 areas where they were previously present. The main causes were found to be: presence of signal crayfish, Pacifastacus leniusculus (40%), habitat alterations (13%) and climatic drought (11%). In 35% of the cases, the reasons could no be determined. Disappearances that were associated with presence of signal crayfish were assigned to crayfish plague. These disappearances have occurred a few years after an increase in the number signal crayfish fishery areas. The new populations of P. leniusculus followed a patchy distribution, and were clearly associated with human introductions. This work shows that signal crayfish currently represents the main reason for decline of indigenous crayfish and that humans play a major role in the dispersal of these carriers of the causative organism of crayfish plague, A. astaci.

The Crayfish Plague in the Czech Republic - Review of Recent Suspect Cases and a Pilot Detection Study

“…The same situation is present in other European countries (e.g. Germany, Great Britain, Finland, Spain, and Sweden), where crayfish plague outbreaks are presently not rare, and are related to the spread of non-native crayfish (mostly the signal crayfish Pacifastacus leniusculus) (HOLDICH, 2003;BOHMAN et al, 2006;DIÉGUEZ-URIBEONDO, 2006). …”

The continuing spread ofPacifastacus leniusculusin Carinthia (Austria)

“…Today P. leniusculus is the most common crayfish species by occurrence in most of the investigated catchments and especially widely distributed in the main rivers. There are numerous examples in other European countries, where the introduction of the signal crayfish had the same or similar impacts (Peay and Rogers, 1999;Savolainen et al, 2003;Huber and Schubart, 2005;Bohman et al, 2006;Bramard et al, 2006;Diéguez-Uribeondo, 2006;Johnsen et al, 2007). The estimated expansion rates of P. leniusculus were quite high compared to other studies (Guan and Wiles, 1997;Peay and Rogers, 1999;Bubb et al, 2005;Huber and Schubart, 2005), although especially in the Glan catchment it was hard to follow, if the expansion was human-mediated or due to active migrations.…”

Aphanomyces astaciPsI-genotype isolates from different Finnish signal crayfish stocks show variation in their virulence but still kill fast

“…The PsI-genotype, which is one of the two known genotypes currently causing crayfish plague epidemics in Finland and other Nordic countries, has its original North American host species, the signal crayfish (P. leniusculus), present in Europe (Souty-Grosset et al, 2006). The signal crayfish has been intentionally introduced to inhabit most of the continental Europe (Westman, 2000;Souty-Grosset et al, 2006), thus assisting in the spread of the PsI-genotype crayfish plague (Unestam, 1969;Persson and Söderhäll, 1983;Diéguez-Uribeondo and Söderhäll, 1993;Diéguez-Uribeondo, 2006;Souty-Grosset et al, 2006). These A. astaci PsI-genotype strains could likely have had less pressure to adapt to novel European habitat than Asgenotype strains, since they have easy access to host habitat that is often available as a result of signal crayfish introductions (Jussila et al, 2013a).…”