Abstract

This laboratory study assessed the effects of nickel on the behaviour and some blood parameters of African catfish, Clarias gariepinus, after a 96 h semi static method with a view to determining the safe concentration effect of the metal physiological functions of the fish. The mortality rate increased with increased concentrations of toxicants. The 96 h median lethal concentration (96 h LC₅₀) was 8.87mg Ni/l using the logarithmic method with dose-mortality regression line Y (% mortality) = 174.74 (log Concentration) – 97.711. All the blood parameters (erythrocyte, leucocytes, hematocrit and hemoglobin count) decreased with increasing concentration of toxicant and become significantly lower (P < 0.05) at higher concentration when compared with the control. The derived hematological indices of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were equally lowered. It is believed that observed depression in hematocrit and hemoglobin values coupled with decreased and deformed erythrocytes are obvious signs of anaemia. In conclusion, the changes observed indicate that hematological parameters can be used as an indicator of Ni related stress in fish on exposure to elevated Ni levels.

Key words: Nickel, Clarias gariepinus, hematology, stress, fish, 96 h acute toxicity