Calanus oil as a natural source for flesh pigmentation in Atlantic salmon (Salmo salar L.)

The present study was to understand how efficiently the astaxanthin in Calanus oil is utilized for flesh colouration in Atlantic salmon (Salmo salar). Postsmolts of the fish (309 g) were held at 7.9 degrees C and they were fed diets containing 20 or 60 mg astaxanthin per kilogram feed derived from a synthetic source or from Calanus oil for 181 days. Besides growth and feed intake assessments, at day 81 and 181, fish flesh were subjected to colour analysis and astaxanthin determination. Growth and feed performance did not vary between the groups. There were significant differences in the amount of astaxanthin in muscle between almost all groups both at day 81 (P < 0.05) and at day 181 (P < 0.001). However, a notable similarity between fish receiving 20 mg astaxanthin from the synthetic source and those receiving 60 mg astaxanthin from Calanus oil (P > 0.05) at day 181 indicated that comparable amounts were deposited only with the greater level of the natural source. Tristimuli colorimeter a* values support the analytical results at day 181. Although Calanus oil did serve as a natural dietary pigment source for farmed salmon, its inclusion level should provide more than 60 mg astaxanthin per kilogram feed to achieve colouration preferred by the market.