Alleviation of transportation-induced stress in Nile tilapia, Oreochromis niloticus, using brackish water

Fish transportation is associated with drawbacks such as stress, hydromineral imbalance, and oxidative stress. Thus, it worth finding methods to improve fish health and welfare during transportation. Adding salt to transportation water decreases osmotic stress and energy expenditure; thus, the objective of this work was to evaluate the effects of different concentrations of salt (0, 2, and 4 g/L) added in the transportation water on the stress and antioxidant parameters of Nile tilapia, Oreochromis niloticus, after 3 h transportation. The fish (38.2 ± 2.69 g) were sampled before (control), immediately and 24 h after transportation. After transportation, there were elevations in the plasma cortisol and glucose levels in all treatments; however, the salt-treated fish exhibited lower elevations in these parameters. The plasma sodium, chloride, and the hepatic alanine aminotransferase activity decreased; whereas the plasma total protein, albumin, and the hepatic malondialdehyde and lactate dehydrogenase significantly increased after transportation in 0 g/L salt treatment. The plasma sodium level stayed decreased after 24 h recovery in 0 g/L salt treatment; whereas, the hepatic alanine aminotransferase decreased in 4 g/L salt treatment, at this time. After transportation, there were significant elevations in the hepatic superoxide dismutase and glutathione peroxidase, as well as significant decreases in the hepatic glutathione reductase, aspartate aminotransferase, and reduced glutathione in 0 and 2 g/L salt treatments. The hepatic superoxide dismutase and glutathione peroxidase remained elevated, after 24 h recovery in 0 g/L salt treatment. There were significant decreases in the hepatic CAT activity after transportation in the salt-treated fish, and after recovery in all treatments. In conclusion, addition of 4 g/L salt to transportation water reduces stress, hepatic damage and oxidative stress, and hydromineral imbalance in Nile tilapia