Status of Pacifastacus leniusculus and its role in recent crayfish plague outbreaks in France: improving distribution and crayfish plague infection patterns
Abstract
Aphanomyces astaci, the crayfish plague pathogen, is responsible for mass mortalities in native European crayfish stocks. Its persistence and spread across Europe has been facilitated by the presence of invasive North American crayfish species, which act as asymptomatic vectors of this pathogen.
In France, some recent mass mortalities have involved the pathogenic strain harboured by the invasive signal crayfish, Pacifastacus leniusculus, which may share habitats with the autochthonous white-clawed crayfish, Austropotamobius pallipes. To improve the efficiency of conservation management of A. pallipes, we have (i) updated information on the distribution of P. leniusculus populations in France based on data collected by the ONEMA (French National Agency for Water and Aquatic Environments), (ii) studied the distribution and prevalence of the crayfish plague pathogen within P. leniusculus populations throughout the country, and finally (iii) genotyped the strains responsible for several recent mass mortalities in A. pallipes populations.
In total, 1658 populations of the signal crayfish were recorded in France; 1554 of these in streams and 104 in ponds. In 2014, this species was present in 80 of 95 French departments.
Among the 1131 analyzed P. leniusculus individuals from 94 localities, 255 individuals (23%) tested positive for A. astaci presence. Infected individuals were detected in 63% of studied populations.
Local prevalence varied highly among populations, ranging from 0% (no detection of A. astaci) up to 90% in the most infected ones. Out of five mass mortalities characterized in France in 2014-2015, four involved the strain from genotype group B, specific to P. lenisuculus.
Our results confirm that the widespread signal crayfish serves as a key reservoir of A. astaci in France and therefore represents a serious danger for native crayfish species, especially the white-clawed crayfish.