Inter-individual variation in total fatty acid compositions of flesh of Atlantic salmon smolts-fed diets containing fish oil or vegetable oil

Fish such as Atlantic salmon (Salmo salar L.) are a natural source of n-3 highly unsaturated fatty acids (HUFA) eicosapentaenate (EPA; 20:5n-3) and docosahexaenoate (DHA; 22:6n-3), which are essential for protecting humans against cardiovascular diseases. Thus, flesh n-3 HUFA level is a trait of considerable importance in farmed fish, particularly now that the fishmeal and fish oil (FO) components of traditional aquaculture diets have to be replaced by more sustainable alternatives including plant meals and vegetable oils (VO). The present study aimed to characterize the inter-individual variation in this trait in a single strain of Atlantic salmon. Fish were grown for 12 weeks on either an FO diet, or a diet with 100% of the FO replaced by a VO blend containing rapeseed, linseed and palm oils, flesh n-3 HUFA content and composition determined, and the variation between individuals characterized. The results showed that, irrespective of diet, variation exists in the content of n-3 HUFA in the flesh of individual salmon, showing that individual animals can display an enhanced ability to maintain high levels of n-3 HUFA in their flesh. The pros and cons of defining the trait on a qualitative or quantitative basis are discussed