Fig. 5. Plasma levels of cortisol in isolated juvenile rainbow trout fed an experimental wet feed supplemented with 1.5 % (experiment 1) or 0.15 % (experiment 2) L-tryptophan (TRP) for 7 days. In both experiments, the control fish were fed the same experimental wet feed but without supplementary tryptophan. Intruder-tested fish were subjected to resident/intruder tests (see text for details). Values are means + S.E.M. (intruder-tested, N=10–12; non-tested, N=6–12).