Effects of Salinity Changes on Hematological Blood Parameters and Stress Responses in Red Tilapia (Oreochromis spp.) Infected with Vibrio harveyi

The effect of salinity manipulation on the blood parameters and stress responses of red tilapia, Oreochromis spp. During infection with Vibrio harveyi was investigated. The fish were reared in five different salinities (0, 5, 10, 15, and 20 ppt) with three replicates for 30 days and were injected with 10⁶ CFU/mL V. harveyi intramuscularly in all treatments except the negative control. After infection, the fish were observed for clinical signs for 14 days, collected blood samples, and measured stress responses in 0, 2, 3, 4, 5, 6, 7, and 14-days post-infection (dpi) with V. harveyi, meanwhile the cortisol plasma was taken on 0, 2, 3, 4, 5, and 6-dpi. The analysis of blood parameters consisted of total erythrocyte count (RBCs), total leucocyte count (WBCs), hemoglobin (Hb) level, percentage of monocytes (Mon), lymphocytes (Lym) and neutrophils (Neu). The stress response parameters included primary responses (cortisol plasma), secondary responses (blood glucose), and tertiary responses (ventilation rate). The results indicate that salinity manipulation influenced the resistance of red tilapia after infection with V. harveyi.