Effects of light regime on diurnal plasma melatonin levels and vertical distribution in farmed Atlantic cod (Gadus morhua L.)

摘要: Abstract Two studies were performed to study the effect of different light intensities on melatonin secretory profiles in Atlantic cod ( Gadus morhua L.). In an indoor tank study, plasma measured over a 24-hour cycle juvenile reared under 12 h light:12 h dark photoperiod, having either high or low daytime intensity (15.5 0.16 μE·cm − 2 ·s − 1 ). second levels kept traps at three depths (4, 9 and 14 m) large sea cage following exposure five experimental regimes: (1) natural (NL), (2) NL + artificial constant (LL) 2, 7 12 m depth, (3) NL + LL 2 12 m, (4) 2 m (5) together with additional surface shading. The vertical distribution free swimming same was monitored using hydroacoustics. experiment, diurnal similar intensity, remaining during period, then increasing rapidly within 15–30 min lights off, before peaking around midnight. fish NL showed rhythm levels, although sunrise started fall earlier 4 m depth compared 14 m. Overall, most effectively reduced, terms relative (day/night) those sampled deepest (14 m). Relative correlated distance from artificial source ambient light. Dispersed (lamps 12 m) effective regime for inhibiting nocturnal rise ratios all depths. Finally, regimes did not influence cage, which consistently remained close bottom cage.