This study investigated firstly, the impact of ploidy on growth performance and whole body composition of Atlantic salmon at different early freshwater stages (34 dph (days post-hatching) alevin; 109 dph; fry and 162 dph parr;) and secondly, whether phenotypic differences at these stages were reflected in the protein samples collectedproteome from whole fish, white muscle or liver tissue. Female diploid and triploid Atlantic salmon (n = 3) were first fed at 35 dph and then maintained by feeding to satiation on commercial feeds.