Population genetics of Atlantic salmon (Salmo salar) in the River Shannon system in Ireland: An appraisal using single locus minisatellite (VNTR) probes

Single locus minisatellite DNA analysis was applied to a population genetic study of Atlantic salmon (Salmo salar) from the River Shannon system in Ireland. Following the construction of a hydroelectric scheme near the base of the 340 km long river in 1929, an extensive supplemental stocking programme commenced in 1960 (initially using Canadian ova). Samples of up to 100 wild parr were collected from nine different tributaries, with temporal sampling from three Of these tributaries. A total of 1252 fish were screened for four minisatellite loci, using three minisatellite probes (pSsa-A45/1, pSsa-A45/2, and pStr-A9). Three of the loci were highly variable (Ssa-A45/1, Ssa-A45/2/1, and Str-A9), revealing 9, 10, and 8 resolvable alleles, respectively, when all samples were considered. Mean heterozygosities per locus were 0.61, 0.67, and 0.71 for the three loci, respectively. While the salmon from the tributaries below the hydro-electric scheme appeared distinct from those above, the differentiation detected in the upper system was attributed primarily to genetic drift resulting from poor escapement of adult salmon to some of the upper tributaries. No Canadian-specific alleles were detected at the fourth locus (Ssa-A45/2/2).