We describe genetic variation at three microsatellite single loci and six allozyme loci of seven natural Atlantic salmon populations from Ireland and Spain. A comparison of genetic variability detected at both types of loci is performed. Also, the relative value of microsatellite single locus variability with regard to the identification of individual salmon populations is assessed. Microsatellite loci are shown to display higher levels of variation than allozyme loci.Mean number of alleles (6 1.53) and heterozygosity (0.46 0.04) at microsatellite loci are greater than those found for allozymes (1.85±0.05 and 0.21±0.03, respectively), and some microsatellite alleles appear to be specific for a location or geographical area. Allozyme and microsatellite variation show the same pattern of differentiation between populations with Irish and Spanish populations grouped into different clusters. However, greater values of genetic distance were found among microsatellite (D = 0.0747±0.011) rather than among allozyme loci (D = 0.0449 0.008). These results provide evidence that microsatellite-based analysis of genetic variation will be useful in the identification of individual populations of Atlantic salmon.

No abstract

No abstract

ABSTRACT. The presence of Aeromonas salrnonicida, the etiological agent of furunculosis, was examined using polymerase chain reaction (PCR) and DNA probe methodology in wild Atlantic salmon Salmo salar taken from 3 Irish river systems Blood samples from 61 individual fish were examined and the presence of pathogen was determined in 87% of the fish examined. However, the level of pathogen was extremely low, calculated at less than 100 A. salmonicida genome equivalents per fish. These data imply a widespread low level infection of A. salmonicida amongst wild salmon in Irish rivers.

A repetitive element was isolated from the genome of Atlantic salmon. Nucleotide sequence analysis revealed the existence of variant monomers that range in length from approximately 200 to 230 bp. Repeat monomers contain regions of cryptic simplicity, internal repetition, and long direct repeats with deletions and insertions between individual units. The repetitive element was shown to have a tandem unit arrangement and was estimated to occupy between two and three percent of the Atlantic salmon genome. Southern blot analysis revealed the repetitive element to be unique to Atlantic salmon and brown trout species. In situ hybridization analysis showed this element to be localized at the main nucleolar organizer region bearing chromosomes of Atlantic salmon (Salmo salar), AS cell line (derived from S. salar), and brown trout (Salmo trutta).