Pigment-depletion in Atlantic salmon (Salmo salar) post-smolt starved at elevated temperature is not influenced by dietary carotenoid type and increasing α-tocopherol level

<div><p>Pigment-depletion in the fillets of farmed Atlantic salmon (<em>Salmo salar</em>) arises after periods of elevated water temperatures with voluntary starving. This study tested the effects of dietary pre-loading with different pigment carotenoids (astaxanthin and/or canthaxanthin) combined with two α-tocopherol levels (normal and high: 500 and 1000 mg/kg, respectively) on pigment-depletion <em>in vivo</em> in Atlantic salmon after four weeks of challenge. We also tested whether oxidative stress manifested as an underlying depletion mechanism.</p><p>Carotenoid levels in whole fillet homogenates were not decreased significantly post-challenge but fillet α-tocopherol concentrations were increased significantly in contrast to decreased oxidative stress indices. However, image analysis revealed localised fillet pigment-depletion following all dietary treatments. These data imply that localised pigment-depletion was not prevented by pre-loading of the fillet with different carotenoid-types/mixtures and increased of α-tocopherol levels from normal to high, respectively. Further, we suggest that oxidative stress might not facilitate pigment-depletion <em>in vivo</em>.</p></div>