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A recent PCR-test developed for identification of Aphanomyces astaci , the organism responsible for crayfish plague, provided false positives for Aphanomyces frigidophilus , Aphanomyces repetans , and some Saprolegnia spp. Real-time PCR showed that with the designed primers, A. astaci and A. frigidophilus cannot be distinguished. The results of this study show that this particular crayfish plague PCR-test ought to be improved and that molecular-based techniques need to be contrasted to histological evidences and disease history.

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 white-clawed crayfish, Austropotamobius pallipes, is the only native species of freshwater crayfish in Spain. This species sustained a first-magnitude inland fishery up to the end of 1970's, when the crayfish plague struck the Spanish waters. It is detected an overall loss of distribution area of populations inhabiting the medium and lower reaches of the main river catchments, especially in Southern and Central Spain. The number of surviving populations can be estimated in ca. 700. Remaining native crayfish populations currently inhabit marginal areas. The populations are very fragmented, occupy short stretches, and are frequently isolated from the main river system. The current distribution is the result of a sum of different factors, i.e. crayfish plague, habitat alterations, extreme climatic drought, etc. The incidence and relative importance of each one varied during the last 15 years, with crayfish plague being a predominant negative factor in the seventies and eighties, and climatic drought in the nineties. The current trend of disappearance is a sufficient reason to consider the native crayfish as at risk of extinction. However neither the national legislation nor most of the regional government legislations have listed this species as endangered. An analysis of the legislation dealing with freshwater crayfish in Spain shows : (a) an uneven and generally low level of protection given to the native species and (b) a very complex fishing and commercialization regulations for crayfish that show significant changes from one region to another. This complex legislation, complemented with a general lack of data on crayfish populations, low levels of management and public involvement, and different strategies in regional governments regarding restocking programs with exotic species, makes a confusing situation. In order to decrease the general tendency of regression of A. pallipes a conservation program for this species needs to be implemented in Spain. This program should include a number of regulations to be followed for the particular autonomous regions of Spain. This program should include measures : (a) to restore native crayfish populations, i.e. by translocations or stocking with farm raised of summerlings, in designated areas where the risk for crayfish plague outbreaks is low, (b) to control the spread of introduced species, by controlling their means of dispersal which usually occurs by human activities, i.e. trade of live crayfish, exotic crayfish stocking programs, crayfishing, aquaculture purposes, etc., and by developing eradication methods for unwanted crayfish populations ; (c) to increase the surveillance of remaining native populations by providing the areas with native crayfish the protection level required by the European Community Directives for the Conservation of Natural Habitats and Wild Flora and Fauna (92/43/EEC and 97/62/EU) ; and finally (d) to improve public and administration awareness.

Cet article decrit les essais entrepris pour proteger ou retablir en Navarre, Espagne, des populations menacees de l'ecrevisse autochtone, Austropotamobius pallipes. Trois especes prosperent actuellement en Navarre, l'espece autochtone, A. pallipes, et les especes americaines introduites, Pacifastacus leniusculus et Procambarus clarkii. Ces deux dernieres especes sont connues comme porteuses du champignon Aphanomyces astaci dans leurs cuticules et comme vecteurs transmettant ce parasite aux especes autochtones. Les strategies de gestion arretees par les Autorites pour restaurer les populations d'ecrevisses autochtones sont discutees.

This work describes the presence of the microsporidian parasite, Thelohania contejeani in some populations of Austropotamobius pallipes of the province of Alava, Spain. This paper constitutes the first report of the presence of this parasite in Spain.

Depuis 1978, une serie d'epizooties correspondant a la «peste» des ecrevisses, dont l'agent responsable est le champignon Aphanomyces astaci, s'est produite en Espagne. En consequence, la plupart des populations de l'ecrevisse patrimoniale Austropotamobius pallipes a ete decimee par cette maladie. Cet article decrit l'etat actuel de la maladie dans les populations d'A. pallipes depuis 1978 et la situation actuelle qui en resulte. De plus, le premier diagnostic de la maladie est decrit depuis 1978 et le premier isolement du champignon est realise a partir d'un stock d'A. pallipes infectees et mortes sur le territoire espagnol.