Some aspects of sustained training of rainbow trout, Salmo gairdneri Richardson

Groups of 6‐7 cm length rainbow trout, Salmo gairdneri Richardson, were simultaneously trained at four water velocities (0, 1·4, 2·2 and 3·5 Ls ‐1 ) for a period of 46 days. Oxygen consumption and swimming ability (fatigue time) were then measured. Only training at 3·5 Ls ‐1 increased the swimming ability of the fish. A study of the relative proportion of the white and red muscles indicated that the white muscle was increasing its mass at velocities in excess of 2·2 Ls ‐1 . The oxygen consumption rate of the trained fish was lower than that of the untrained fish when considered over the whole velocity range.