Human interventions have often led to the admixture of previously allopatric lineages,notably for salmonid species. In France, intensive stocking of Atlantic brown trout has led to a mosaic of outcomes regarding hybridization and introgression of Mediterranean alleles by Atlantic ones. To understand and predict this diversity dynamic, we developed an individual-based demo-genetic model, which implements identified reproductive isolation mechanisms – female preference and gene-by-environment embryonic survival – between both lineages.