Metabolic Profile of Senegalese Sole (Solea senegalensis) Muscle: Effect of Fish–Macroalgae IMTA-RAS Aquaculture

The aquaculture sector is essential for meeting seafood demand while ensuring sustainability. It involves farming fish, mollusks, crustaceans, other invertebrates, and algae in controlled environments, helping to conserve marine resources and reduce ecological pressures. Sustainable practices, such as an integrated multitrophic recirculating aquaculture system (IMTA-RAS) with fish and seaweed, can minimize the environmental impact of fish aquaculture. However, the impact of the introduction of macroalgae on the fish muscle metabolism has not been studied. This research examines the impact of growing Senegalese sole (<i>Solea senegalensis</i>) together with sea lettuce (<i>Ulva ohnoi</i>) on fish metabolism using high-resolution ¹H-NMR-based metabolomics. Three farming systems were compared. These were E₁, a recirculating aquaculture system (RAS); E₂, an IMTA-RAS integrating <i>U. ohnoi</i> for biofiltration; and E₃, an IMTA-RAS with <i>U. ohnoi</i> and <i>Phaeobacter</i> sp. strain 4UAC3, a probiotic bacterium isolated from wild <i>U. australis</i> known to counteract fish pathogens. A metabolomic analysis revealed that energy metabolism was enhanced in IMTA-RAS and even more in IMTA-RAS-<i>Phaeobacter</i>-grown fish, increasing overall metabolic activity. These results indicate that the presence of the algae with the probiotic had a clear impact on the physiological state of the fish, and this deserves further investigation. This study contributes to the understanding of the physiological responses of fish to innovative aquaculture practices, supporting the development of more sustainable and efficient management that reduces the environmental impact and increases fish health and welfare.