EFFECTS OF FISH OIL ETHYL ESTERS ON BODY COMPOSITION AND LIVER OXIDATIVE STRESS IN EUROPEAN SEABASS (DICENTRARCHUS LABRAX) UNDER THERMAL CHALLENGE

Marine heatwaves driven by climate change threaten aquaculture sustainability by disrupting physiological homeostasis, particularly metabolism and oxidative balance, especially in Mediterranean species such as European seabass (Dicentrarchus labrax). Nutritional strategies to improve thermal resilience are increasingly needed. Fish oil (FO), rich in n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), faces sustainability challenges and is being used directly for human consumption. Ethyl esters (EE), derived as by-products from FO refining during omega-3 supplement production, have recently emerged as a potential alternative lipid source. EE oil is rich in EPA and DHA, but the lipids are in the form of ethyl esters rather than triglycerides, which may influence fish lipid metabolism and their response to stress conditions. Previous studies have shown that while EE oil has shown promising results under normal conditions, its impact during thermal challenges has not yet been explored. Thermal stress can alter membrane fluidity, whose composition is modulated by the dietary lipid source. Therefore, understanding the effects of dietary inclusion of EE oil under thermal stress conditions is important. This study evaluates the effects of dietary EE oil on body composition, fatty acid profile, and liver oxidative stress in seabass under simulated heatwave conditions.