Pure and admixed brown trout (Salmo trutta) populations in the Upper Danubian contact zone

Increasing rates of hybridization and introgression in managed populations of freshwater fish are a major threat to the long-term viability of native species. For brown trout (Salmo trutta Linnaeus, 1758) in the Upper Danube drainage, this task is complicated by the presence of both naturally and anthropogenically induced admixture of highly divergent lineages (Atlantic & Danubian). Herein, a ddRADseq protocol was used to type 377 individuals from 24 populations in the Upper Danube in Austria and Germany, as well as from reference populations from adjacent drainages and commercial hatcheries.