Fig. 3. Feed intake, determined as the amount of feed (dry mass) consumed per kilogram of body mass, of isolated juvenile rainbow trout after being transferred to observation aquaria. On day 7, the commercial trout feed was exchanged for an experimental wet feed supplemented with 1.5 % (experiment 1) or 0.15 % (experiment 2) L-tryptophan (TRP). In both experiments, the control fish were fed the same experimental wet feed but without supplementary tryptophan. Feed intake was not registered on day 6. Values are means ± S.E.M.