A comparison of farmed, wild and hybrid Atlantic salmon (Salmo salar L.) reared under farming conditions

The present study compared salmon of farmed, wild and hybrid origin in a simulated aquaculture production cycle from egg fertilisation through approximately 17 months of marine cage rearing. The study was repeated for two year classes. At slaughter, the farmed salmon were over twice the size of wild salmon, whilst hybrids were intermediate. Condition factor was considerably higher in farmed contra wild salmon, with hybrids displaying intermediate or similar values. Maturation was only observed in the second year class, nevertheless, only mature males were observed within the farmed salmon, and only mature females were observed in the wild salmon. Hybrids displayed an intermediate maturation pattern. The percentage of age 1 smolts was considerably higher in farmed contra wild salmon. For most of the quality traits recorded: fat content, fatty acid composition, skin colouration, flesh texture, blood and muscle pH, only moderate differences were observed among the three groups. This is especially true when fish weight, which is closely linked with many of these traits, was accounted for. Nevertheless, observed differences in astaxanthin concentration among the three groups were significant even when the relationship to size was accounted for. It is concluded that the observed differences are genetic in origin, and are either the direct result of selection, or have hitch-hiked with selected traits.