Thermal stress effect on tilapia Oreochromis mossambicus (Pisces : Cichlidae) blood parameters

The effect of thermal stress on blood parameters of Oreochromis mossambicus (Peters, 1852) was evaluated based on the critical thermal maximum (CTMax) and the upper incipient lethal temperature (UILT). The CTMax values in tilapia acclimated at 24, 28 and 32 degrees C were 41.6, 42.0 and 43.3 degrees C, respectively. In fish acclimated at 24 degrees C, the UILT was 38 degrees C and in tilapia maintained at 28 and 32 degrees C resulted in 39 degrees C. The CTMax and UILT responses modified the following blood parameters of O. mossambicus acclimated at different temperatures: coagulation time, sedimentation rate, mean corpuscular volume, haematocrit, number of erythrocytes and leukocytes, percentage of lymphocytes and granulocytes, number of thrombocytes, osmotic pressure and glucose concentration. Glucose concentration was consistently altered by the CTMax and the UILT in all treatments and may be a good indicator of O. mossambicus thermal stress.