Fig. 5. Spectral sensitivity of natural, untreated steelhead smolts. The data for each of four individual smolts are shown separately (two in which dorsal sensitivity was measured and two in which ventral sensitivity was measured). The data have been displaced on the y-axis so that the data from each fish can be easily viewed. The mass of each fish is shown to the right of each data set. Pigment absorptance curves and the linear-additive model were plotted for each individual fish as described in Fig.2, and the values for the ultraviolet (K_U) and short-wavelength (K_S) mechanisms are also shown for each data set.