| Summary: | International audience This study combines otolith trace element and genetic analyses to explore the origin of individuals when hatcheryreared fish are released into wild populations. We sampled 90 juvenile Atlantic salmon (Salmo salar) in four rivers in Normandy (France) and in the hatchery stock. Individuals were analyzed at six microsatellite markers and their otolith elemental concentrations (14 elements) were measured using femto-second laser ablation inductively-coupled plasma mass spectrometry. Wild populations were genetically differentiated from the hatchery strain (FST ≈ 0.06). Significant differences in elemental concentrations were found among otoliths of juveniles from the four rivers and the hatchery, allowing the identification of their geographic origin (830% correct assignment). Coupling genetic and trace element analyses on the same individuals provided formal evidence that hatchery-born juveniles released into the wild can migrate to the sea and return as adults to breed on natural spawning grounds. Their progeny have pure hatchery pedigrees but have otoliths typical of riverborn juveniles, meaning that they can be mistaken for hatchery-raised juveniles if only genetic data are considered. The presence of hybrids also confirmed that individuals with hatchery pedigrees can breed with wild conspecifics. Notre étude combine des analyses d'éléments en trace dans les otolithes et des analyses génétiques pour déterminer l'origine des individus lorsque des poissons élevés en pisciculture sont relâchés dans des populations sauvages. Nous avons prélevé 90 jeunes saumons atlantiques (Salmo salar) dans quatre rivières de Normandie (France) et dans le stock de pisciculture. Chez ces individus, nous avons analysé six marqueurs microsatellites et déterminé les concentrations en éléments (14 éléments) de leurs otolithes par spectrométrie de masse à plasma à couplage inductif avec ablation au laser femtoseconde. Généralement, les populations sauvages se différencient génétiquement de la souche de ...
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