The PCR primer and TaqMan MGB probe sequences used for quantification of the genes encoding 18S rRNA, S20 ribosomal protein, β-actin, GAPDH, EF1A A and EF1A B , are shown in Table 1 . Four of these genes, 18S, β-actin, EF1A A and EF1A B , have also been used as references in real-time RT-PCR analyses of Atlantic salmon in other recent studies [12, 28] . The primers amplify PCR products between 57-98 basepairs (bp) long, which is within the range of 50-150 bp as suggested by Applied Biosystems for their Taq-Man assays. qPCR assays were designed using Primer Express 2.0 software (Applied Biosystems, Foster City, CA, USA) to select appropriate primer and probe sequences from known Atlantic salmon genes. The mRNA sequences encoding S20 ribosomal protein and GAPDH were obtained from GenBank accession numbers BG936672 and BU693999, respectively (exon-exon borders were not considered). The EF1A A assay was based on a cDNA clone that we reported to the GenBank previously (AF321836), whereas the EF1A B assay was based on the EST BG933853.