Aquafeeds are formulated with a high content of fishmeal as protein source. The fishmeal is usually produced from pelagic fish resulting in a reduction of fish availability for human consumption. Thus, it is important to find appropriate protein substitutes in the production of formulated aquafeeds. Several works reported the positive effect of partial addition of poultry by-product meal (PBM) in aquafeeds for different fish species, and from them it is clear that the total substitution of fishmeal is limited by the unbalance of essential fatty acids. In this work, aquafeeds were designed with the total and partial substitution of fishmeal by PBM and enriched with acid fish silage. The designed aquafeeds were evaluated in the rainbow fish Oncorhynchus mykiss growth. Six diets were formulated at different levels of substitution of fishmeal by PBM pet feed grade (33, 66 and 100%), with and without addition of acid fish silage (FS) from tuna fish by-products. All treatments were formulated to contain similar protein and energy in a factorial random design with three repeti tions. The diet containing 100% enriched PBM (EPBM) showed the highest specific growth rate (2.0% day-1) (P < 0.001), whereas the lowest growth rate was observed with PBM33 without enrichment (1.76% day-1), after 22 weeks treatment These results demonstrate that the addition of FS in an aquafeed containing only poultry by-product meal as protein source improves the growth of rainbow fish. The positive effect of FS, mainly the role of essential fatty acids, is discussed.