The photopic spectral sensitivity of a dichromatic teleost fish (Perca fluviatilis).

Spectral sensitivity curves for the freshwater perch were measured using an operant procedure. Sensitivity peaks were found at 530-560 nm and 660-680 nm. Compared with perch cone pigments (P530(2) and P617(2)), the red-shift of the maximum long wave length sensitivity suggested that opponent interactions between the cone types were responsible for the shape of the curve. The absorptions of the lens and yellow cornea were measured, and used to correct the sensitivity curve. It is suggested that the yellow cornea's function depends on its spectral selectivity. Like goldfish, perch show some aberrant high sensitivity around 400 nm.