Introgression between introduced domesticated stocks and natural populations of brown trout was investigated by protein electrophoresis in three Mediterranean rivers. From each river, one undisturbed site and one, closely located, yearly stocked site were sampled. Comparison of the electrophoretic variation observed in samples from the undisturbed sites with that in the introduced hatchery strains revealed several specifically "domestic" variants. The genetic control of these variants was demonstrated by breeding experiments. The samples collected from the stocked sites showed introgression rates ranging from approximately 0 to 40%. The genotype frequencies observed in these samples suggested that no reproductive barrier exists between introduced and native stocks and that they form random mating populations.

Les prélèvements de dérive en période de décrue réalisés conjointement dans le chenal principal et un chenal secondaire de la Durance ont mis en évidence l'importance de la dérive dans le repeuplement du lit principal. Une partie de cette dérive provient du champ d'inondation temporairement colonisé par les organismes benthiques dispersés, l'autre vient des chenaux latéraux.