Effect of brief exposure of tilapia nilotica to a lethal concentration of nitrite on hematology and survival

Groups of Tilapia nilotica were exposed to 45 mg/l NO2-N for 6 and 24 hours. Their blood were examined for total hemoglobin, methemoglobin, hematocrit, RBCs count and plasma nitrite. After 6 hours exposure there was a significant increase [P <0.005] in hematocrit and RBCs number. After 24 hours exposure there was a significant decrease [P <0.005] in hemoglobin, hematocrit and RBCs number while, there was a significant increase [P <0.005] in methemoglobin and plasma nitrite. Mortality was low [13.3%]. Although, most fish survived the high nitrite concentration, hemolytic anemia may develop due to destruction of erythrocytes by the elevated environment nitrite