PLASMA CAROTENOID CONCENTRATION INDICATES THE AVAILABILITY OF DIETARYASTAXANTHIN FOR ATLANTIC SALMON, SALMO-SALAR

Atlantic salmon with an initial weight of 1.1 kg were fed three extrud ed diets with different amounts of astaxanthin (5, 51 and 61 mg kg(-1) ) in an experiment lasting for 26 weeks. Availability of astaxanthin w as assessed after collection of blood plasma from 2 X 10 fish per pen (three pens per diet; two groups of fish per pen, previously unpigment ed and pigmented prior to the start of the experiment). The salmon wei ghed 2-2.5 kg at the time of blood sampling. Correlations were made be tween mean values for plasma carotenoid concentration and dietary asta xanthin concentration, flesh carotenoid concentration at 24 weeks of f eeding, and the amount of carotenoids (mg) retained in flesh per kg bo dy weight increase. There were no differences observed in plasma astax anthin concentration between salmon which were pigmented or unpigmente d prior to the study. The correlation between plasma astaxanthin conce ntration and dietary astaxanthin concentration was r = 0.90. Plasma as taxanthin concentration and mg astaxanthin retained in flesh per kg bo dy weight increase were also highly correlated (r = 0.92), as was the correlation between plasma astaxanthin concentration and flesh caroten oid level (r = 0.95). Plasma astaxanthin concentrations ranged from 0. 5 to 5 mu g ml(-1).