The gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax) require n-3 long-chain polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), for optimal growth and health. Due to the rapid growth of global aquaculture the quantity of marine oils used in aquafeeds has been limited, yet the overall quantity of oil in an aquafeed has increased by the addition of vegetable oil (VO) to supply dietary energy. For aquaculture to continue to grow more fish must be produced with less marine ingredients, yet EPA and DHA must be maintained at levels above fish requirements. This project set out to re-evaluate the requirement for EPA and DHA in gilthead seabream and European seabass. Two dose-response studies were designed and executed where juvenile seabream and seabass were fed one of six levels of EPA+DHA (0.2 – 3.2 % as fed). Biometric data were collected and analysed to determine new requirement estimates for EPA+DHA for fish of two weight ranges (24 – 80 g and 80 – 200 g). The effects of the dietary LC-PUFA gradient on lipid composition and metabolism were also considered.