Fig. 1. Food intake, as percentage of body mass, of isolated juvenile rainbow trout after being transferred to observation aquaria. On day 7, the commercial trout feed was exchanged for feeds supplemented with L-tryptophan to a level corresponding to two (2x, open squares), four (4x, open circles), or eight (8x, open triangles) times of that of the non-supplemented control feed (1x, filled triangles). Values are means ± S.E.M. from 5-7 individuals.