L'Ecrevisse à pattes blanches ou Austropotamobius pallipes est un des organismes sentinelles des rivières françaises dont le déclin accompagne la dégradation progressive des masses d'eau superficielle. Les programmes de repeuplement pour la conservation de l'espèce s'inscrivent dans le cadre de la restauration écologique et de la surveillance de la bonne qualité des milieux. Pour leur réussite, il est nécessaire de pouvoir évaluer le potentiel d'un site à être repeupler. En ce sens, le présent travail a proposé l'emploi des éphéméroptères et de la matière organique comme indicateurs. L'étude a été menée sur des ruisseaux de têtes de bassin des Deux-Sèvres qui constituent encore des sites à A. pallipes. La présence de certaines familles d'éphéméroptères (Leptophlebiidae) est corrélée avec la présence de cette écrevisse. Ces indicateurs biologiques ont prouvé leur efficacité dans le cadre de campagne de repeuplements réussis. Les propriétés de fluorescence de la matière organique expriment le fonctionnement des milieux et par extension leur qualité. Un modèle statistique bâti sur ces propriétés permet également de prédire la probabilité de présence ou d’absence d’A. pallipes pour un site donné. Les deux indicateurs proposés dans ce travail ont montré leur potentiel pour servir d'outil à la réintroduction de cette espèce. / White-clawed crayfish (Austopotamobius pallipes) is a sentinel organism in French rivers. Its decline follows the progressive degradation of the masses of water surfaces. Restocking programs for the conservation of this species take place in the frame of ecological restoring and monitoring of good environment quality. For their success, it is necessary to evaluate the potential of a site to be repopulated. In this sense, the present work proposes the use of Ephemeroptera (Leptophlebiidae) and Organic Matter as indicators. This study was conducted in headwater streams of the Deux-Sèvres region (France), which are suitable sites for A. pallipes. The presence of certain species of mayflies is correlated with the presence of this white-clawed crayfish. This biological indicator had proven its efficiency under a succeeded restocking campaign. The fluorescence properties of the Organic Matter express the functionning of the sites and by expansion their quality. A statistical model built on these properties also allows to predict the probability of a site for the presence or absence of A. pallipes. Two indicators proposed in this work have shown their potential toserve as a tool for the reintroduction of this species.

De novembre 2002 à décembre 2005, l'habitat préférentiel de l'écrevisse indigène à pattes blanches (Austropotamobius pallipes) a été défini dans le « pays de Gâtine » (Deux-Sèvres, France). Pour cette étude, huit cours d'eau, répartis dans quatre bassins hydrographiques différents, ont été sélectionnés. Sur chaque ruisseau, deux points de prélèvement ont été choisis : le premier, le plus en amont, était situé au niveau de la population d'A. pallipes et le second, 2 à 3 km en aval, était dépourvu d'écrevisse à pattes blanches. Vingt-trois paramètres physico-chimiques, concernant les composantes minérale et organique de l'eau, ont été très régulièrement mesurés et quatre prélèvements de la faune de macroinvertébrés benthiques ont été réalisés. Ce suivi a permis d'acquérir une importante base de données pour caractériser les tolérances d'A. pallipes vis-à-vis de certains paramètres ce qui nous a conduit à discuter son statut de bioindicateur de la qualité des eaux. L'utilisation d'analyses multivariées (Analyse en Composantes Principales majoritairement) a montré (i) que la matière organique serait un des facteurs discriminants dans la présence/absence d'A. pallipes et (ii) que, précisément, la présence d'A. pallipes est associée à celle de familles de macroinvertébrés les plus sensibles aux pollutions organiques. L'ACP a aussi permis de réduire considérablement le nombre de paramètres abiotiques et biotiques informatifs. De plus, l'utilisation de ces paramètres sélectionnés pour modéliser par Réseaux de Neurones Artificiels (RNA) la présence/absence d'A. pallipes a fourni des résultats satisfaisants et prometteurs en terme de gestion et de conservation de cette espèce menacée.

This thesis is composed of two parts - research part, focused on field research of occurence and abundance of the Stone Crayfish and the Noble Crayfish in the basin of Zákolanský stream, and a pedagogical part, project Crayfish in the Czech Republic and their protection, aimed for grammar school students. The literature outline summarizes contemporary knowledge about all five species of crayfish in the Czech Republic. Our native species are the Stone Crayfish (Austropotamobius torrentium) and Noble Crayfish (Astacus astacus). The non-native are Narrow-clawed Crayfish (Astacus leptodactylus), Spiny-cheek Crayfish (Orconectes limosus) and Signal Crayfish (Pacifastacus leniusculus). Aside from the chapters concerning the particular species and their determination, the literature outline also contains general information about the life and endangerment of crayfish. I have conducted the field research from April to September 2009. I also noted and evaluated the environmental conditions of the crayfish habitats. Based on the adjusted AOPK ČR methodology, I selected eight 100-meter long brook-sections of the Europe-important locality of Zákolanský stream, with the previously confirmed occurrence of crayfish. From the eight sections, I found crayfish only in three. All the captured specimens were of the...

This thesis deals with monitoring the occurrence of crayfish in selected river basins in the western Bohemia, considering the human impact on freshwater ecosystems and his influence on crayfish and other aquatic organisms. The selected river basin territory was Úhlava, Úslava and Otava. In the localities, numerical and species-wise representation of crayfish was monitored by finding data from the Agency for Nature Conservation and Landscape of Czech Republic database. The flow and environment characteristics were also monitored. This thesis focuses on water quality in streams of selected major river basins, Úhlava, Úslava and Otava rivers in the period from 2006 to 2011. Results of the findings show a sympatric occurrence of original species, stone crayfish (Austropotamobius torrentium), noble crayfish (Astacus astacus) and part of the original danube crayfish (Astacus leptodactylus) with invasively spreading species of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus). With respect to this fact, the sensitivity of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus) are evaluated in a form of own test results on acute toxicity. The thesis compared current results of occurrence and the protection of crayfish in the Czech Republic and abroad. The conclusion of this thesis is a proposal of a freshwater biomonitoring system, using the crayfish.

Aquatic invasive species are a major threat to native freshwater biodiversity. The North American signal crayfish Pacifastacus leniusculus was introduced to Great Britain during the 1970s and is now widely distributed throughout England, Wales and Scotland. First recorded in Scotland in 1995, P. leniusculus is now established at more than twenty sites. The only other introduced crayfish species present in Scotland is the white-clawed crayfish Austropotamobius pallipes. A. pallipes is restricted to only two locations in Scotland, Loch Croispol and Whitemoss Reservoir. P. leniusculus negatively impacts macrophytes, invertebrates and fish though ecological and physical processes. Additionally, P. leniusculus has displaced A. pallipes throughout much of its native range within Great Britain due to competition and disease. Consequently, the two A. pallipes populations in Scotland have a high conservation value. This PhD study aimed to improve understanding of P. leniusculus invasion success by examining trophic dynamics and to develop methodologies that could improve the detection and control of P. leniusculus populations in Scotland. Stable isotope analysis was used to determine the diet composition, trophic position and whether an ontogenetic dietary shift occurs in the Loch Ken population of P. leniusculus. Bayesian mixing models indicated that P. leniusculus in Loch Ken do exhibit an ontogenetic dietary shift. Additionally, individuals of all sizes occupied the trophic position of a predator in Loch Ken suggesting that invertebrates and fish constitute an important component of P. leniusculus diet. Stable isotope analysis was used once again to compare the isotopic niche width and diet composition of P. leniusculus populations from Loch Ken and A. pallipes populations from Loch Croispol and Whitemoss Reservoir. At the species level, A. pallipes exhibited a larger niche width than that of P. leniusculus. At the population level, the isotopic signatures of the A. pallipes populations were considerably different from each other suggesting an overestimation of A. pallipes’ niche width at species level. Results showed no dietary overlap between species and Bayesian mixing models suggested P. leniusculus and A. pallipes were consuming different resources, indicating there would be no direct competition for food resources if they were to co-occur. A plus-maze study was used to determine if P. leniusculus exhibited a preference for one of four food attractants (Oncorhynchus mykiss, P. leniusculus, beef or vegetation), which could be used to improve trapping efficiency. In the maze system, P. leniusculus exhibited no preference for any food attractant presented. This would suggest that either the maze was not a good model or food attractants would not improve trapping efficiency of P. leniusculus. Additionally, a comparative investigation into the use of gill nets as a method to control P. leniusculus was conducted. Results showed that the net type and the presence of fish entangled in the net influenced the number of P. leniusculus caught. Finally, environmental DNA (eDNA) was used and evaluated for detection of P. leniusculus. A robust quantitative Polymerase Chain Reaction (qPCR) assay and DNA extraction protocol were developed. Using the developed qPCR assay, P. leniusculus eDNA was detected in controlled aquaria conditions but not in environmental water samples collected from the field. Furthermore, the quantities of P. leniusculus eDNA declined in aquaria conditions while individuals were still present suggesting the mechanisms for eDNA release by P. leniusculus are complex. Stable isotope analysis indicates that P. leniusculus exhibit an ontogenetic dietary shift, and in each life stage, P. leniusculus function as an omnivore but occupy the trophic position of a predator. Niche width analysis revealed that the diet of P. leniusculus was less general than that observed in A. pallipes and thus diet of P. leniusculus may not be responsible for invasive success. Food attractants will not enhance trapping efficiency but nets may present a potential new method to control P. leniusculus. Similarly, eDNA presents a promising new method for rapid detection of P. leniusculus. It will not be possible to eradicate P. leniusculus in Scotland but the findings of this PhD may help prevent establishment of new populations. These results should be incorporated into future management strategies for P. leniusculus populations in Scotland and may have broader applications in Great Britain and Europe.