Genetic variation at traditional and novel allozyme loci, applied to interactions between wild and reared Salmo salar L (Atlantic salmon)

This study aimed to increase the number of allozyme loci which may be screened in the Atlantic salmon, Salmo salar L., particularly for use in investigating interactions between wild populations and reared strains. Three samples of wild salmon from Ireland, Scotland and Spain and one from a farmed strain of Norwegian origin were used as index samples. Other Irish samples were used in technique development. Ninety-one enzyme loci were resolved, including 21 not previously screened in S. salar. Thirteen loci were found to be variable, including three novel polymorphic loci (EST-5*, FBALD-3* and TPI-3*). Two novel alleles (sAAt-1,2*130 and sAAT-3*83) were also detected. Levels of variability were lowest in the Spanish sample. The farmed strain had levels of (H) over bar and (P) over bar lower than those in the two other wild samples. Mean levels of (H) over bar and (P) over bar were higher than those reported previously in studies that used a smaller number of loci but confirm S. salar as one of the less variable salmonids. Nine of the 13 variable loci showed significant population differentiation, the most discriminatory being mMEP-2*. The discriminatory power of the novel variable loci was in the middle of the range of those of the other loci. (D) over bar values reflected the relative geographical locations from which the samples originated. There were significant dines in allele frequencies at mMEP-2* and TPI-3*. Fourteen enzyme loci including six variable loci were resolved in adipose fin.