The increased consumption and thus market demand for aquaculture products results in the continued growth of aquaculture production, which is the fastest growing agricultural sector. Fish feed contains variable levels of FMFO (Fish Meal and Fish Oil), which originates from capture fisheries and is used as a source of protein and omega-3 fatty acids. Therefore, FMFO is an unsustainable feed ingredient. Microalgae rich in LC-PUFA can serve as a sustainable alternative and even to and improve fish health. The aim of this study was to investigate the use of microalgae as a substitute for FMFO in the diet of a carnivorous fish, the Asian sea bass (Barramundi; Lates calcarifer).
Three different species of microalgae were incorporated into fish diets, including Nanochloropsis oceanica (N), Isochrysis galbana (I) and Porphyridium purpureum (P) with no FMFO. The diets were formulated to maintain constant protein and omega-3 fatty acid contents. These diets were fed to juvenile barramundi for a period of 8 weeks and compared to a commercial control diet. Results revealed better growth and resistance to bacterial challenge in fish fed with microalgae-based diets. Immunostimulation was demonstrated in the algae-fed fish by biochemical and gene expression analyses. These results hold a promise to the development of FMFO-free fish feed for the carnivorous barramundi. The study validates the potential of microalgae, which are primary producers of these high valued fatty acids, as well as protein, in commercial aquaculture nutrition.