Abstract Local adaptation is often portrayed as uniform fitness disadvantages of immigrants relative to locals. Yet dispersal costs vary with origin, sex and life-history traits, shaping the balance between gene flow and adaptation. We quantified these heterogeneous costs by comparing the reproductive success (RS) of local and immigrant individuals using a 15-year genetic pedigree of Atlantic salmon (Salmo salar), including over 1100 adults and 3400 juveniles. Immigrants represented 19.5% of adu