Viability of wild populations is commonly affected by anthropogenic habitat destruction and fragmentation. Fishery pressure has heavily depleted fi sh resources during last decades (Millenium Ecosystem Assessment 2006). Therefore, salmonid populations rendered small because of human interference into natural habitats could have reduced genetic variation. In order to support the affected wild populations, stocking of fi sh with hatchery origin is a commonly employed management strategy in salmonid conservation. Conservation strategies, however, should be based on the precautionary principle, which intends to minimize possible genetic risks for wild populations. Risk for population viability from reduced genetic variation of hatchery produced stocking salmon populations is emphasized in theoretical and empirical studies (e.g., Ryman and Laikre 1991; Araki et al. 2007). For example, under favourable conditions of culture, hatchery practices can affect crucial life-history traits and promote rapid juvenile growth, resulting in increased proportions of precociously mature males and shorter life-span (Jonsson and Jonsson 2006). After partaking in just few generations of hatchery breeding for supportive breeding purposes, captive-reared hatchery fi sh may become locally adapted to hatchery environment and consequently can erode locally adapted alleles if interbred with native fi sh from an endangered salmon population it originally intended to relieve from extinction risk, because of inherently lower survival and fi tness in the wild (reviewed in Ferguson et al. 2007).