Future growth of aquaculture depends on the discovery of alternative sources of protein to feed fish. Plant-derived proteins lack sufficient levels of two essential amino acids, methionine and lysine, for fish dietary requirements. W e examined differences between a genetically selected line of rainbow trout that grows more rapidly on a plant protein diet when compared to a non-selected line. We hypothesize genetically selected rainbow trout uptake these two limiting amino acids more efficiently in their gut via more numerous amino acid transporters as compared to non-selected fish. Amino acid uptake and total amino acids were assessed over time in plasma using [13C] and [15N ] stable isotopes of methionine and lysine measured by LCMS . Amino acid transporter expression in the gut was assessed using qPCR. R esults show amino acid uptake in rainbow trout selected for growth on a plant-protein diet is greater than the uptake observed in non-selected fish. Quantitative PCR of amino acid transporters in the proximal intestine also show increased expression stimulated by lysine over time consistent with levels amino acid of uptake.