Effets des mesures de gestion halieutique sur la conservation d'une espèce vulnérable : le brochet (Esox lucius)

L'objectif de cette thèse a été de déterminer la pertinence des lâchers comme mode de gestion des pêcheries récréatives de brochet (Esox lucius). Une synthèse bibliographique a d'abord permis d'identifier les potentialités et les risques liés aux lâchers de brochets. La construction d'une vaste base de données sur les lâchers et sa mise en relation avec des données de pêche électrique a permis de démontrer que les lâchers ont un effet positive sur l'occurrence du brochet mais pas d'effet sur son abondance malgré que l'efficacité des lâchers augmente avec la taille des poissons lâchés. Deux études génétiques ont permis de mettre en évidence un fort taux d'hybrides permis les juvéniles et un taux relativement modéré parmi les adultes. D'une manière générale, les lâchers un bon potentiel d'amélioration des pêcheries mais présentent des risques pour la conservation de l'espèce. Ce travail se termine par des recommandations sur l'usage des lâchers et une réflexion sur les stratégies alternatives de gestion.The objective of this PhD was to determine the relevance of stocking for pike (Esox lucius) recreational fisheries management. First, we identified benefits (for recreation) and risks (for conservation) of stocking of pike through a bibliographic review. Second, we used a large dataset (96 sites, 6 years) to evaluate the actual and potential effects of stocking on pike populations. We found that pike stocking programs actually positively affect pike occurrences but not pike abundance despite we found that the effect of stocking on pike abundance increases with the size of the stocked pike. Third, we measured the genetic impact of stocking. We found a high rate of hybridization among juveniles but a moderate rate of hybridization among adult pike. Overall, stocking has good potential to enhance fisheries yet it carries conservation risks. We conclude with recommendations for the use of stocking and discussion about alternative management strategies

Impact of recreational fisheries management strategies on the conservation of a vulnerable species : pike (esox lucius)

L'objectif de cette thèse a été de déterminer la pertinence des lâchers comme mode de gestion des pêcheries récréatives de brochet (Esox lucius). Une synthèse bibliographique a d'abord permis d'identifier les potentialités et les risques liés aux lâchers de brochets. La construction d'une vaste base de données sur les lâchers et sa mise en relation avec des données de pêche électrique a permis de démontrer que les lâchers ont un effet positive sur l'occurrence du brochet mais pas d'effet sur son abondance malgré que l'efficacité des lâchers augmente avec la taille des poissons lâchés. Deux études génétiques ont permis de mettre en évidence un fort taux d'hybrides permis les juvéniles et un taux relativement modéré parmi les adultes. D'une manière générale, les lâchers un bon potentiel d'amélioration des pêcheries mais présentent des risques pour la conservation de l'espèce. Ce travail se termine par des recommandations sur l'usage des lâchers et une réflexion sur les stratégies alternatives de gestion.The objective of this PhD was to determine the relevance of stocking for pike (Esox lucius) recreational fisheries management. First, we identified benefits (for recreation) and risks (for conservation) of stocking of pike through a bibliographic review. Second, we used a large dataset (96 sites, 6 years) to evaluate the actual and potential effects of stocking on pike populations. We found that pike stocking programs actually positively affect pike occurrences but not pike abundance despite we found that the effect of stocking on pike abundance increases with the size of the stocked pike. Third, we measured the genetic impact of stocking. We found a high rate of hybridization among juveniles but a moderate rate of hybridization among adult pike. Overall, stocking has good potential to enhance fisheries yet it carries conservation risks. We conclude with recommendations for the use of stocking and discussion about alternative management strategies

Situations expérimentales de communication en mathématique

Balacheff Nicolas, Guillerault M., Laborde C. Situations expérimentales de communication en mathématique. In: Langage et société, supplément au n°17, 1981. Pratiques langagières et stratégies de communication. Terrains, méthodes d'enquête et d'ananlyse. pp. 30-34

Catch‐related and genetic outcome of adult northern pike Esox lucius stocking in a large river system

International audienceGenetic introgression from stocked adult northern pike Esox lucius to a wild self‐recruiting population was detected in a large river system and some stocked E. lucius survived up to two spawning seasons and dispersed over several kilometres in the river. Moreover, the catch rate of stocked E. lucius by anglers was low (9.6%), hence suggesting that the efficiency of stocking activity is questionable

Does the non-native European catfish Silurus glanis threaten French river fish populations ?

International audienceThe European catfish, Silurus glanis, was widely introduced in western Europe, and it has now established self-sustaining populations in numerous large rivers of western France. Using data collected from surveys conducted by the French National Agency for Water and Aquatic Environment (Onema) from 1989 to 2010 in more than 500 sites throughout the country (10636 electrofishing surveys), we investigated the potential impact of the European catfish on fish communities in French rivers. In the first part of the analysis, we compared trends observed before and after the European catfish was established at given sites (before-after analysis). Species richness, evenness and diversity decreased significantly after the European catfish was established at 1.4%, 1.4% and 5.8% of the sites, respectively. Total fish biomass and density decreased significantly at 6.6% and 2.9% of the sites, respectively. In the second part of the analysis, we compared sites with European catfish against sites lacking European catfish during the same period (with-without analysis). Fish species richness was significantly higher in sites with European catfish. No significant differences in fish diversity, evenness, total fish biomass or density were found between sites with or without European catfish. While our results indicate that the European catfish may in a few cases impact fish communities or populations, it does not appear to be responsible for a countrywide collapse in fish assemblages