Response of tissue lipids to diet variation in Atlantic salmon (Salmo salar): Implications for estimating diets with fatty acid analysis

The influence of feeding duration and tissue type on fatty acid (FA) deposition in Atlantic salmon (Salmo salar) tissues was investigated to establish the appropriate foundation for quantitative estimates of diet in wild fish. Fish were adapted to seawater and were fed one of four formulated diets based on krill or herring oil for 22 weeks. After 12 weeks of feeding, proportions of most FA in both belly flap and muscle tissues of salmon had changed substantially to resemble dietary FA proportions, showing little variation after an additional 10 weeks of feeding. However, tissues showed a differential response to diets, depending on the proportions of dietary FA. When present in large proportions in the diet, FA, including 18:2n-6 and monounsaturated FA, seemed to be selectively catabolized; when present in low proportions, selective retention in tissues occurred. Proportions of the polyunsaturated FA, 20:5n-3 and 22:6n-3, in tissues also varied with diet but not in a predictable manner related to dietary FA proportions. Further, the response to a change in the FA profile of diet was not equal for both tissues with belly flap tissue developing a FA signature that was more similar to the diet than muscle tissue. These results suggest that fish may represent a more complex study species than marine mammals for quantitative estimation of diet using FA.

► Feeding duration and tissue type influenced fatty acid (FA) deposition in salmon.
► Tissue fatty acids were similar to the FA profile of a new diet after 12 weeks.
► Belly flap tissue developed a FA profile more similar to diet than muscle tissue.
► Estimating diet in fish using FA may be more difficult than in marine mammals.