Lopes, Tiago da SantaCostas, BenjaminRamos-Pinto, LourençoPimentel, ChristopherPinto-Cunha, FranciscoReynolds, PatrickImsland, Albert K. D.Aragão, CláudiaFernandes, Jorge M. O.2026-01-072026-01-072025-122352-5134http://hdl.handle.net/10400.1/28059The expansion of lumpfish use as a cleaner fish has recently come to a halt, in part due to the concerns around their welfare. While refining handling procedures and operational standards is necessary, improving aquafeeds has the potential to alleviate the burden caused by chronic stress. This study examined the influence of different inclusions of dietary branched-chain amino acids (BCAAs) and lysine (Lys) on lumpfish health, immunity, stress response, growth and plasma amino acid profiles for 10 weeks. Stress and metabolic biomarkers (cortisol, lactate, glucose, triglycerides) showed modest but measurable alterations, such as lower triglycerides and higher glucose in fish fed the diet with limiting Lys and BCAAs. Metabolic differences were also visible from plasma amino acid profiles. Limiting Lys and BCAAs in diets seems to increase the glucogenic activity in stressed fish, increasing glucogenic amino acid levels in plasma. Diets with increased Lys and BCAAs levels increased antiprotease activity and lowered GABA plasma concentrations. These findings suggest that Lys- and BCAAs-enriched diets might provide relevant nutritional support, which allows the organism to adapt to a mild chronic stress. Immunonutrition can prove to be an effective strategy to ameliorate welfare in the face of chronic stress.engLumpfishStressAmino acidsWelfareImmunityBCAALysinejournal article10.1016/j.aqrep.2025.103235