Managing fish populations under mosaic relationships. The case of brown trout (Salmo trutta) in peripheral Mediterranean populations

摘要

Brown trout were collected from 36 locations in the Iberian Peninsula representing the southwestern extreme of this species' distribution in Mediterranean drainages. Allelic distributions among these peripheral populations for 26 polymorphic allozyme loci (corrected to remove effects of introgression from exogenous hatchery introductions) indicated a mosaic pattern both within and among drainages. This distribution was interpreted to reflect reticular evolutionary processes involving multiple colonization episodes by distinct lineages, secondary intergradations, and drift. under this scenario, management to conserve native gene pools differs from that commonly used under hierarchical structures (such as in Atlantic Iberian drainages) where geographic patterns could justify regional stocking of indigenous fish in adjacent unsampled areas. Because such action risks erosion of native populations in the present case, remedial efforts should focus on habitat recovery and environmental education programs, and harvest sustained by natural reproduction.