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Represented by 137 populations in 1978, A. pallipes is now almost completely restricted to only one department, with 45 populations recorded, representing a decrease of 68% of the population number in 25 years, with a loss of 40% of populations in the last 6 years. Most of the disappearances of crayfish are unexplained. For the 22 others, the main reasons of the disappearance of indigenous crayfish populations were due to (1) habitat destruction by channelisation, (2) decrease of water quality by use of agricultural chemicals, (3) the construction of ponds or lakes changing the physical and chemical parameters of brooks inhabited by indigenous crayfish, (4) the introduction of non-indigenous species, mainly P. leniusculus and recently (5) crayfish plague implicated and characterized in the disappearance of two populations, two additional ones being suspected.Introduced in 1978 in Vienne department, P. leniusculus has now been found in 28 locations. First record of P. clarkii was in 1988 in Charente-Maritime department; since it has spread in most of the hydrographic basin of this department. La plupart des disparitions de populations sont inexpliquées. Pour les disparitions dont les causes peuvent être présumées ou observées, on trouve par ordre décroissant d'importance : (1) la destruction de l'habitat (recalibrage), (2) la diminution de la qualité de l'eau par utilisation de produits chimiques pour l'agriculture, (3) la construction de mares ou d'étangs qui changent les paramètres physico-chimiques des cours d'eau (4) l'introduction d'écrevisses non indigènes, principalement P. leniusculus et récemment (5) la peste de l'écrevisse qui a été caractérisée dans la disparition de 2 populations, et suspectée dans 2 autres cas.Introduite en 1978 dans le département de la Vienne, P. leniusculus est présente dans 28 sites (de ce département). Les premières observations de P. clarkii datent de 1988 en Charente-Maritime, depuis elle s'est étendue à la plupart des bassins hydrographiques de ce département.

The white-clawed crayfish, Austropotamobius pallipes pallipes, still has a wide-spread distribution in France, but since the last century, populations have declined because of habitat alteration (due to human disturbance) and have been also eliminated by crayfish plague, for which introduced exotic species are a vector. Action plans for the conservation of A. pallipes are urgent and if recovery programmes are to be initiated in France, then it is important to estimate how much genetic variation is partitioned between remaining populations as the species is being currently threatened in all its European distribution. We show how a new molecular marker can be used to study crayfish populations. Mitochondrial DNA (mtDNA) variation in natural populations was examined by restriction fragment length polymorphism analysis in samples taken from fifteen French populations and six European populations representative of three subspecies observed in A. pallipes in order to examine the extent of differentiation between populations. Biogeographic considerations about the genetic distances observed between the three subspecies are made. The study reveals a low level of genetic variation among English, Welsh and most of French populations, corresponding to a genetic stock uniformity among A. pallipes pallipes.The only two French populations exhibiting a high level of intrapopulational genetic variation are in fact mixed samples : the comparison with results obtained in European populations revealed that the first population was composed of the two subspecies A. pallipes pallipes and A. pallipes italicus and the second of A. pallipes italicus and A. pallipes lusitanicus.Results proved that some repopulations, performed in the past from A. pallipes italicus and supposed having failed, have been successful and that the French stock did not correspond to the only subspecies A. pallipes pallipes. A first analysis of genetic variance observed on a regional scale revealed that there was no genetic structure according to basins and could reflect human-mediated movement of crayfish stocks between these basins. Consequently, mtDNA is an essential marker to GÉNÉTIQUE ET CONSERVATION DE L'ÉCREVISSE À PATTES BLANCHES AUSTROPOTAMOBIUS PALLIPES : UTILITÉ DU MARQUEUR MITOCHONDRIAL.RÉSUMÉ L'écrevisse à pattes blanches Austropotamobius pallipes pallipes a encore une large répartition en France mais, depuis le siècle dernier, les populations ont été sérieusement réduites à cause de la dégradation des habitats suite à l'activité humaine et ont également été décimées par la peste de l'écrevisse, suite aux introductions d'espèces d'écrevisses exotiques. Si des actions de conservation d'A. pallipes sont urgentes à mettre en place, elles ne peuvent se faire sans une estimation préalable de la variabilité génétique des populations chez cette espèce actuellement en voie de disparition. La variabilité de l'ADN mitochondrial (ADNmt) dans les populations naturelles est examinée par polymorphisme de la longueur des fragments de restriction à partir...

A survey of the macroinvertebrates of three brooks harbouring the white-clawed crayfish was conducted in Haute-Vienne department (France). Its aim was to increase our understanding of these ecosystems to help the conservation of A. pallipes. These brooks run through pastoral areas with well-developed riparian vegetation, which offers an important shade. Water temperature, dissolved oxygen concentration, pH, and conductivity fell within the ranges found for this species. A total of 34, 31, 29 taxa and 1 502, 1 364, 2 707 individuals of macrobenthos were collected in Holme, Besque and Bellecombe streams, respectively. Results showed good to very good water quality with IBGN scores ranging from 15 (Bellecombe) to 17 (Holme and Besque), reflecting a limited impact of the anthropogenic disturbances. Taxa diversity were high for Holme and Besque with Shannon index around 3.2, translating a great heterogeneity of habitat and an equilibrated faunal community. Bellecombe showed a limited diversity with Shannon index of 1.42, resulting from the presence of numberous Chironomidae. This brook suffers probably weak organic pollution which could be related to the low water flow observed during the sampling. The similarity test according to Jaccard index showed high percentage of common taxa among ETP (Ephemeroptera-Trichoptera-Plecoptera) between all sites. The high similarity of benthic macroinvertebrate communities could be an useful criteria to identify brooks for restocking purpose.Keywords: Austropotamobius pallipes, macroinvertebrates, biotic indices, rivers, water quality. ÉTUDE DE LA QUALITÉ BIOLOGIQUE DE L'EAU DE L'HABITAT DE L'ÉCREVISSE À PATTES BLANCHES, BASÉE SUR LES COMMUNAUTÉS DE MACROINVERTÉBRÉS :UTILITÉ POUR SA CONSERVATION RÉSUMÉUne étude des macroinvertébrés de trois cours d'eau hébergeant des populations d'écrevisse à pattes blanches a été menée dans le département de la Haute-Loire (France). Son but est d'améliorer notre compréhension de ces écosystèmes pour aider à Article available at