How selective breeding has changed farmed Atlantic salmon and what the welfare implications of rapid genetic change are for this species.
The genetics of farmed Atlantic salmon represent a welfare frontier that receives less attention than husbandry practices but may be equally important. Selection for growth rate has been so intense that the resulting fish can be physiologically compromised — their hearts and skeletons may struggle to support their artificially rapid development. Cataracts affecting a significant proportion of some farmed salmon cohorts are a welfare concern, as are the cardiac anomalies associated with extreme growth. At the same time, genetic work is actively improving welfare in some dimensions: salmon with reduced sea lice susceptibility need fewer stressful treatments, a genuine welfare benefit. The challenge is ensuring that breeding objectives include welfare criteria alongside production metrics.