The Effect of Salinity Variation on the Blood Profile and Physiological Adaptation of Nile Tilapia (Oreochromis niloticus)

Abstract

Nile tilapia (Oreochromis niloticus) is a major freshwater aquaculture species with potential for culture in brackish environments, but increasing salinity may impose osmotic stress and alter physiological performance. This study evaluated the effects of salinity on the blood profile, survival, and physiological adaptation of Nile tilapia. A completely randomized design was used with five salinity treatments (0, 5, 10, 15, and 20 ppt), each with three replicates. Hematocrit, hemoglobin concentration, erythrocyte count, leukocyte count, blood glucose concentration, survival rate, and water quality were assessed. Increasing salinity significantly affected the hematological and physiological responses of Nile tilapia. Erythrocyte counts and hemoglobin concentrations decreased as salinity increased, whereas leukocyte counts, hematocrit values, and blood glucose concentrations increased. Survival tended to decline with increasing salinity, with the lowest value (73.33%) recorded at 20 ppt. These responses indicate increasing osmoregulatory and metabolic stress at higher salinity levels. Under the conditions tested, salinity levels of ≤10 ppt provided a more favorable range for maintaining physiological stability and survival of Nile tilapia.