Fig. 5. Diel differences in spectral electroretinograms (ERGs) of weakfish, spotted seatrout, red drum, Atlantic croaker and spot. Differences were calculated by subtracting the day spectral sensitivities (S_day) from night sensitivities (S_night). Dashed gray lines are ±95% CI, calculated as 1.96^* (s.e.m.). Values above the horizontal zero line (i.e. positive) indicate wavelengths of greater response during daylight, those below the zero line (i.e. negative) indicate wavelengths of greater nocturnal response. Significant differences occurred when CI did not encompass zero.