Toxic stress and hematological effects of nickel on African catfish, Clarias gariepinus, fingerlings

Abstract

This laboratory study assessed the effects of nickel on the behavior 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 anemia. 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.