Focal melanization in the skeletal muscle of farmed Atlantic salmon is a great welfare and economic problem in the aquaculture industry. The focal discoloration is a result of a chronic inflammation in the skeletal muscle. This condition has not been observed in wild Atlantic salmon, thus the cause of the inflammation may be due to both external and internal (genetic) factors. The aim of the current study was to minimize the external impact, and possibly reveal a potential genetic factor contributing to the condition. Atlantic salmon of farmed, wild and hybrid origin were kept in identical rearing conditions. Growth parameters and presence of focal discoloration was registered at several time points. The dataset contain data from each sampling.