Assessing Thermal Stress in Silver Barb (Barbonymus gonionotus): Oxidative Stress and Biochemical, Hematological, Hormonal, and Operculum Responses Within Survival Temperature Range

This study investigates the biochemical and physiological responses of the economically important fish Barbonymus gonionotus to acute temperature fluctuations. Focusing on malondialdehyde (MDA) levels in serum and visceral organs, serum biochemical indices, hematological parameters, cortisol levels, and operculum movement, this research assessed the impacts of thermal stress. Experimental conditions involved two thermal regimes: heat shock at 25–29 °C and 25–37 °C; as well as cold shock at 25–21 °C and 25–13 °C sustained over 24 (D1), 48 (D2), and 72 (D3) h. Serum MDA levels increased significantly. Notably, MDA in the gills, brain, and liver fluctuated under cold stress, particularly at 13 °C. Serum parameters showed significant alterations except for AST, total protein, and cholesterol, which remained unaffected by heat shock. Red blood cell (RBC) counts dropped to their lowest at 13 °C, while white blood cell (WBC) counts diminished significantly when temperatures dropped to 21 °C and then stabilized. Cortisol surged with temperature changes, peaking at 13 °C and 29 °C for cold and heat shock, respectively. Operculum movement was inversely affected by thermal changes, decreasing with cold and increasing with heat. These findings underscore the sensitivity of silver barb to thermal extremes, providing insights for optimized aquaculture management and enhanced resilience to environmental stressors.