Response of fish assemblages to environmental variations by bayesian hierarchical modeling: a case study of cyprinid fish juveniles in the upper river Rhone. ; Etude des réponses des assemblages de poissons aux variations de l'environnement par modélisation hiérarchique bayésienne : Application aux juvéniles de cyprinidés du Haut-Rhône

Understanding how fis assemblages vary is a major goal of ecology and bioindication. In this PhD thesis, advanced statistical tools were used to identify which descriptors of temperature and flow regimes, that are among the most essential components of fish natural environment, do generate interannual variations of juvenile assemblages of cyprinid fish in the upper River Rhone. By using datasets of water temperature, flow and electric fishing samples over the 1980-2005 period, three groups of species have been determined based on their synchrone response to environmental variations and have been used to develop to types of Bayesian hierarchical models : - a Poisson regression, for which a selection of variable was performed, using the Bayes Factor criterion. this first model allowed for the quantification of the effects of the selected variables on the interannual variations of the different species abundance. - a model with shared latent variable, assuming the existence of a common source of variation for the environmental and the biological data, the Hypersignal. This model underlined the relative importance of the environemental variables in determining the assemblages structure. While their effects are generally treated separately, the joint effect of the temperature and flow regimes on the structure and the interannual variations of juveniles fish assemblages was put forward here. ; La compréhension des déterminismes des communautés de poissons et de leurs variations est un enjeu majeur, tant en écologie qu'en bioindication. Dans ce travail doctoral, nous avons mis en place des outils de statistiques avancées afin d'identifier les aspects des régimes thermique et hydrique, constituants essentiels de l'environnement naturel des poissons, responsables des variations des assemblages de juvéniles de cyprinidés du haut Rhône. En utilisant des chroniques de températures de l'eau, de débits et d'échantillonnages par pêche électrique sur la période 1980-2005, nous avons déterminé trois groupes d'espèces présentant ...