Dietary vitamin C can alleviate the lethal effects of extreme temperature on juveniles of cobia Rachycentron canadum

Abstract

Marine heatwaves (MHWs) and extreme temperatures can severely impact farmed fish’s growth and immune response. Diet vitamin C supplementations (hereafter vitamin C) can enhance fish performance, but it remains to be tested whether vitamin C can help the fish cope with extreme temperatures. In this study, cobia (Rachycentron canadum) juveniles were reared under two temperatures (30°C and 34°C) with three levels of dietary vitamin C (0, 200, and 400 mg/kg diet). We evaluated the fish growth and immune response in relation to the energy intake from the feed utilization. Exposure to 34°C caused fish mortality in the control and at 200 mg/kg vitamin C, but not at 400 mg/kg vitamin C, suggesting that high vitamin C supplements can mitigate the lethal heat stress. The effect of vitamin C on reduced growth, protein, and lipid content was independent of temperature and this may be associated with the pattern of the feed utilization. Extreme temperature also reduced the white and red blood cells, hematocrit, and lysozyme, but the vitamin C supplement could mitigate or reduce the heat stress on these parameters. These results underscore the importance of vitamin C in helping cobia juveniles cope with the heat stress from MHWs.

Keywords

• Ascorbic acid
• Cobia
• Rachycentron canadum
• Heat stress
• Innate immunity
• Marine heatwaves