Spectral sensitivity of rainbow trout (Salmo gairdneri).

The photopic spectral sensitivity of the rainbow trout, Salmo gairdneri, was determined using a two choice appetitive training method. The resulting curve had three maxima at around 391-473, 490-573 and 650-669 nm. Maximum sensitivity was reached with short wavelength stimuli. Thresholds for white light were also obtained. The results show that the rainbow trout has an action spectrum that is similar to that of other fresh water teleosts in similar circumstances, and that it most likely has the ability to distinguish monochromatic stimuli on the basis of wavelength. Using thresholds to white light and typical freshwater visual pigments, the form of the spectral sensitivity curve was found to be best fitted by independent receptor action at the short wavelengths and by inhibitory interaction between the green and red receptors at the longer wavelengths.