show Abstracthide AbstractA full life cycle feeding trial was performed on two groups of Atlantic salmon selected based on their pigment retention (high or low pigment; HP and LP, respectively,) which at first feeding were either offered a diet rich in marine (M) or terrestrial (V) ingredients. The impact that first feeding and genotype has on their gut microbiota was assessed in marine water after fish were fed with a V diet at the final sea water phase. Samples were obtained from the trial, from three different sampling points: end of stimulus (T0), 6 week post sea water transfer, but pre-diet switch (T1), and 14 weeks post-challenge (T2).