Growth Performance and Flesh Quality of Sea Bass (Dicentrarchus labrax) Fed with Diets Containing Olive Oil in Partial Replacement of Fish Oil—With or Without Supplementation with Rosmarinus officinalis L. Essential Oil

This study aimed to investigate the effects of using olive oil (OO) in a partial replacementof fish oil (FO), with or without supplementation with rosemary essential oil (RO), on the growthperformances and flesh quality traits of farmed Dicentrarchus labrax. Sea bass were fed with theexperimental diets for 200 days; afterwards, they were caught and stored in ice (0–2 ◦C) for up to17 days. The specific growth rate (SGR) and feed conversion rate (FCR) were calculated. Filletswere analyzed for physical features, chemical composition, fatty acid profile, and malondialdehyde(MDA) concentration on days 0, 5, 10, and 17 of storage. The fillets were assessed for sensoryproperties according to the QIM and Torry Scheme methods. No statistical differences betweengroups were found for the final average body weight, SGR, FCR and the flesh chemical composition.Supplementation with RO reduced (p < 0.05) MDA concentration, thus improving the shelf life of fishby up to 10 days. The sensory score (QIM) increased linearly (p < 0.05) with storage time; for cookedfillet, the Torry Scheme score decreased (p < 0.05) with storage time. The economic analysis of feedcost has proven the feasibility of using olive oil as local feed ingredient in the partial replacement offish oil.