Omega-3 fatty acids effectively modulate growth performance, immune response, and disease resistance in fish against multiple stresses.

Arsenic pollution and climate change are two major global challenges that have threatened the aquatic environment and to a certain extent led to extinction of aquatic animals. Concerted and accelerated scientific efforts are in progress to restrict the ill- impacts of pollution and climate change in the aquatic ecosystem. In this context, we have conducted a study to delineate the effect of omega-3 fatty acids i.e., eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in mitigating arsenic pollution and temperature stress in Pangasianodon hypophthalmus. Four isocaloric and iso‑nitrogenous diets were prepared viz. control feed (no supplementation), and three treatment groups with combined level of EPA + DHA at 0.2, 0.4 and 0.6%. Fish were reared under arsenic (2.65 mg L−1) and elevated temperature (34 °C) (As+T) stress for 105 days with eight different treatment groups in triplicates. Growth performance, oxidative stress enzymes, stress biomarkers, immunity, lipid profile, bioaccumulation of the arsenic in fish tissues and bacterial infection in terms of cumulative mortality and relative percent survival were altered on exposure of arsenic and temperature stress. Supplementation of combinatorial mixture of EPA + DHA at the rate of 0.2 and 0.4% in the diet led to improved growth performance, anti-oxidative status, immunity of the fish and reduced the infection against Aeromonas hydrophila. Neurotransmitter enzyme, HSP 70 and Vitamin C were significantly enhanced (p < 0.01) with supplementation of EPA + DHA, whereas, total lipid, cholesterol, phospholipid, triglyceride and very low density lipoprotein (VLDL) were reduced (p < 0.01) at 0.2 and 0.4% of dietary incorporation of EPA + DHA. Overall, the present investigation clearly revealed that a novel combination of EPA + DHA at 0.4% has the potential to mitigate arsenic pollution, temperature stress and protect the fish against bacterial infection. • Combinatorial mixture of EPA and DHA mitigate As and temperature stress in fish. • EPA + DHA at 0.2 or 0.4% diet enhanced the anti-oxidative status in fish. • Multiple stress biomarkers was significantly reduced by dietary EPA + DHA in fish. • EPA and DHA also enhanced immunity of fish against As and temperature stress. • EPA + DHA significantly reduced bacterial infection and As bioaccumulation in fish. [ABSTRACT FROM AUTHOR]