Organic certification for aquaculture fish prohibits the use of synthetic pigments in feed but allows natural alternatives. Meal derived from the alien red swamp crayfish (Procambarus clarkii) is rich in astaxanthin, a powerful natural antioxidant. This study aims to evaluate the effects of a 12 % dietary inclusion of crayfish meal on the shelf-life and nutritional quality of farmed gilthead seabream (Sparus aurata). Compared to the control diet, the experimental diet had no negative effects on fish growth. To assess shelf-life, fillets from fish fed the two diets were analyzed at different times: immediately after harvesting (0 days), after refrigeration (4 days), after freezing (30 days), and post-cooking. Fillets from the crayfish-fed group showed a higher proportion of omega-3 polyunsaturated fatty acids compared to the control (26.5 % vs. 23.5 % of total fatty acid methyl esters). Additionally, levels of conjugated dienes and trienes in fish muscle were significantly lower in the experimental group, likely due to the antioxidant properties of astaxanthin. The radical scavenging activity of both feeds and fillets was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, while endogenous antioxidant activity was assessed by thiol group analysis. Both methods highlighted significantly improved antioxidant capacity in fillets from the experimental diet (e.g., 34.5 % vs. 1.1 % for DPPH). Malondialdehyde analysis of refrigerated, frozen, and cooked fillets further confirmed significantly lower lipid oxidation levels in the test group compared to the control. Overall, these findings suggest that crayfish meal can be considered a natural functional ingredient in seabream diets, as its inclusion enhances fillet stability against oxidation.
