Visual spectral sensitivity of photopic juvenile Pacific bluefin tuna (Thunnus orientalis)

Although Pacific bluefin tuna is a species that relies on vision, its photopic visual function is not well known; we therefore recorded electroretinograms to investigate photopic spectral sensitivity in juveniles of this species (49–81 days post-hatch; standard length 74–223 mm). The peak spectral sensitivity wavelength was 505 nm. We estimated that two (λmax = 512–515 nm and 423–436 nm) or three (λmax = 512–515 nm, 423–436 nm, and 473 nm) types of cone visual pigments contribute to photopic vision; these spectral sensitivities are adapted to surface water habitats in clear ocean and coastal water.