Microsatellite polymorphism and the population structure of cod (Gadus morhua

Abstract: Allelic variation in six highly polymorphic microsatellite loci (mean heterozygosity, 86%) provided evidence that cod (Gadus morhua) in the northwest Atlantic belong to multiple genetically distinguishable populations, and further that genetic differences may also exist between northwestern and southeastern cod aggregations within the northern cod stock complex off Newfoundland. Cod were sampled from winter aggregations ranging from Hamilton Bank to the northern Grand Bank in the northern cod complex, and from the Flemish Cap, the Scotian Shelf, and the Barents Sea. Tests of allele frequency homogeneity (χ2), FST, and (δµ)2, allele sharing, and Rogers distance measures revealed significant differences among northern cod, Flemish Cap, Scotian Shelf, and Barents Sea samples. Within the northern cod complex, two pooled samples, NORTH (Hamilton, Funk, and Belle Isle banks) and SOUTH (northern Grand Bank area), were distinguishable using χ2, (δµ)2, and allele sharing measures. Both (δµ)2 and Rogers distances clustered western Atlantic samples in two groups distinct from the divergent Barents Sea sample; one comprised NORTH, SOUTH, and Scotian Shelf, and the other, Flemish Cap. Résumé: La variation allØlique de six loci de microsatellites fortement polymorphes (hØtØrozygotie moyenne de 86%) a mis en Øvidence le fait que les morues (Gadus morhua) du nord-ouest de lAtlantique appartiennent à de multiples populations gØnØtiquement distinctes, et quil peut en outre exister des diffØrences gØnØtiques entre les concentrations de morues du nord-ouest et du sud-est dans le complexe de stocks de morue du nord situØ prŁs de Terre-Neuve. Des morues ont ØtØ ØchantillonnØes dans le complexe de stocks de morue du nord, du banc Hamilton au nord du Grand Banc; sur le Bonne