The formulation of sustainable fish feeds based on plant ingredients supplemented by alternative ingredients to plant (insect, micro-algae, yeast) and genetic selection of fish for plant-based diets were tested on rainbow trout in two separate experiments. Plant-based diets and corresponding diets supplemented with an ingredient mix: insect, micro-algae and yeast in Experiment A, and insect and yeast in Experiment B were compared to commercial-like diets. In experiment A, the mixsupplemented diet was successful in compensating the altered growth performance of fish fed their respective plant-based diet compared to those fed the commercial diet, by restoring feed conversion. In experiment B, the selected line demonstrated improved growth performances of fish fed mixsupplemented and plant-based diets compared to the non-selected line. Metabolomics demonstrated a plasma compositional stability in fish fed mix-supplemented and basal plant-based diets comprising an amino acid accumulation and a glucose depletion, compared to those fed commercial diets. The selected line fed mix-supplemented and commercial diets showed changes in inositol, ethanol and methanol compared to the non-selected line, suggesting an involvement of microbiota. Changes in plasma glycine-betaine content in fish fed the mix-supplemented diet suggest the ability of the selected line to adapt to alternative ingredients. Combined with responsible fishing policies, the increasing demand for aquatic products challenges the development of sustainable and efficient fish feed for aquaculture, which currently provides about 50% of the aquatic products consumed 1. Plant ingredients make up at least 90% of the fish feed used for many fish species, including carnivorous ones such as the rainbow trout 2,3. However, sustainable fish feeds free of marine ingredients are not yet sufficiently performant to guarantee a fair economic income to farmers. Fish feeds can be improved by selecting high-quality plant proteins, or by including alternative ingredients of plants ingredients and fish products, that meet the nutritional requirements of fish, increase farming profitability, and support environmental preservation and consumer expectations. A substantial research effort has been conducted to assess the efficacy of a wide range of alternative ingredients to plant-based feedstuffs, from single-cell ingredients to animal by-products.Read less <