Four isonitrogenous and isoenergetic diets were formulated (MixitWin V. 6.14, Agriculture Software Consultants Inc., USA) to contain 45% crude protein (dry weight) and 10% crude lipid (Table 1). A control diet containing FM as the main protein source (FM100) was made in addition to three plant based-diets (blend of SBM and soy protein concentrate SPC), in which FM was replaced at increasing levels: 20% (FM80), 40% (FM60) and 80% (FM20). In order to achieve a maximum of FO replacement in the experimental feeds, a meal from the n − 3 LC-PUFA-rich, marine heterotroph