Pigmentation of 1, 2 and 3 year old Arctic charr ( Salvelinus alpinus) fed two different dietary astaxanthin concentrations

Abstract

Two dietary astaxanthin levels (63 and 114 mg kg −1) were fed to three year classes (1 +, 2 +, 3 +) of Arctic charr in a 25 weeks experiment. Growth were monitored, and at weeks 1, 13 and 25, samples were taken for analysis of total carotenoids in flesh, skin, fins and plasma. The average growth rates were 1.35, 0.73 and 0.44% d −1 for the 1 +, 2 + and 3 + charr respectively. In the 3 + group, growth rate declined towards the end of the experiment, and this was probably a result of sexual maturation. Carotenoid concentrations in the flesh and skin increased throughout the experiment for the 1 + and 2 + fish. For the 3 + fish, which became sexually mature, carotenoid concentration in the flesh increased during the early part of the experiment and then stabilized, whereas the concentration in the skin showed a marked increase. After 13 weeks of feeding, there was an overall tendency ( P = 0.066) towards a higher flesh carotenoid concentration in the fish fed the 114 mg astaxanthin kg −1diet than in the fish fed the 63 mg kg −1 diet, but no significant differences were observed at 25 weeks. Significant differences between year classes were seen in flesh, skin and plasma carotenoid concentrations. After 13 weeks of feeding, the flesh carotenoid concentrations were lowest in the 1 + and highest in the 3 + fish. At the end of the experiment, no differences were seen between the 2 + and 3 + fish, while the 1 + fish were still less pigmented. The carotenoid concentrations in skin after 13 and 25 weeks and in fins after 25 weeks were higher in the 3 + fish than in the other groups. Estimates of astaxanthin deposition in relation to body weight increase revealed that the 1 + group was less efficient at utilizing dietary carotenoids for flesh pigmentation than the older fish. The efficiency with which the dietary astaxanthin was used for flesh pigmentation decreased when the concentration was increased from 63 to 114 mg kg −1.