Influence of Fenitrothion on Swimming Velocities of Brook Trout (Salvelinus fontinalis)

The critical swimming velocities of brook trout (Salvelinus fontinalis) following exposure to 150, 500, and 1500 μg/liter fenitrothion were 100, 83, and 70%, respectively, of the performance of control fish. This represented 35 and 60% decrease in power output, respectively, for the two higher concentrations.At step-test intervals longer than 15 min, the critical velocity (ca 4.5–5 lengths [L]/s) was reasonably constant. At shorter step-test intervals, the critical velocity increased rapidly to exceed 7 L/s at a step-test interval of 30 s. The cruising speed of control fish was estimated at 4.5 L/s.The influence of fenitrothion exposure on swimming speed is related to previous studies on sublethal effects of fenitrothion and to concentrations in streams resulting from insecticide spraying.