Role of Genetic Refuges in the Restoration of Native Gene Pools of Brown Trout

Abstract:  Captive-bred animals derived from native, alien, or hybrid stocks are often released in large numbers in natural settings with the intention of augmenting harvests. In brown trout ( Salmo trutta ), stocking with hatchery-reared non-native fish has been the main management strategy used to maintain or improve depleted wild brown trout populations in Iberian and other Mediterranean regions. This measure has become a serious threat to the conservation of native genetic diversity, mainly due to introgressive hybridization. Aware of this risk, the agency responsible for management of brown trout in the eastern Pyrenees (Spain) created "brown trout genetic refuges" to preserve the integrity of brown trout gene pools in this region. Within refuge areas, the prerefuge status with respect to fishing activities has been maintained, but hatchery releases have been banned completely. We evaluated this management strategy through a comparison of the stocking impact on native populations that accounted for stocking histories before and after refuge designations and fishing activities. In particular we examined the relevant scientific, cultural, and political challenges encountered. Despite agency willingness to change fishery policies to balance exploitation and conservation, acceptance of these new policies by anglers and genetic monitoring of refuge populations should also be considered. To improve management supported by genetic refuges, we suggest focusing on areas where the public is more receptive, considering the situation of local native diversity, and monitoring of adjacent introgressed populations. We recommend the use of directional supportive breeding only when a population really needs to be enhanced. In any case, management strategies should be developed to allow for protection within the context of human use.