A genetic test of metapopulation structure in Atlantic salmon (Salmo salar) using microsatellites

The principal objective of this study was to describe the pattern of genetic exchange and isolation of Atlantic salmon (Salmo salar) populations among geographical regions of the province of Quebec, Canada. Seven riverine populations, associated with three putative regional metapopulations (North Shore, Gaspe Peninsula, and Ungava), were analyzed using microsatellites. Our results did not support the putative metapopulation structure. Significant heterogeneity in allelic frequency was observed among most rivers independently of their location or group subdivision. Interpopulation genetic variance (φST) indicates less heterogeneity among rivers than χ 2 analysis and was mainly associated with the geographical distance of the most isolated rivers, the Natashquan and the Koksoak. Even with low genetic variance among populations, the overall significant allelic heterogeneity among rivers strongly suggests that each population, whether separated by thousands or tens of kilometres, should be considered and managed as a specific stock. Resume : L'objectif principal de cette etude etait de decrire le degre d'echange genetique entre des populations de saumon atlantique (Salmo salar) appartenant a differentes regions geographiques de la province de Quebec. Sept rivieres, associees a trois metapopulations regionales hypothetiques (Cote-Nord, peninsule de Gaspe et l'Ungava), ont ete analysees a l'aide de microsatellites. Nos resultats ne soutiennent pas une structure composee de metapopulations. Une heterogeneite significative des frequences alleliques entre la majorite des rivieres independamment de leur localisation ou de leur subdivision par region. La variance genetique interpopulation (φST) suggere une heterogeneite entre les rivieres mais a un degre moindre qu'indiques par les χ 2 et etait associee essentiellement avec la distance geographique des rivieres plus isolees, telles que la Natashquan et la Koksoak. Meme si on observe de faibles variances genetiques ou structure de population, l'heterogeneite allelique significative et generale entre les rivieres suggere fortement que les populations, voisines ou separees par des milliers de kilometres, soient considerees et gerees comme des stocks specifiques.