Impact of nickel (Ni) on hematological parameters and behavioral changes in Cyprinus carpio (common carp)

The effect of nickel on hematological parameters and behaviour in Cyprinus carpio after a 96 h exposure to nickel test was investigated. Cyprinus carpio fingerlings were obtained from local fish hatchery. Morphometric characteristics of experimental fish were recorded. Fish of both sexes were stocked without discrimination. The fish were exposed to different concentrations (0, 6, 9, 12, 15 and 18 mg/l) of nickel sulphate using standard screening procedure. The mortality rate of the experimental fish was increased with increase in concentration of nickel. The 96 h median lethal concentration (96 h LC50) was 12.44 mg Ni/L using the logarithmic method with dose-mortality regression line y = 188.224x-86.52. The dissolved oxygen concentration decreased with increase in the level of Ni. All the blood parameters (erythrocyte, leucocytes, hematocrit and hemoglobin count) decreased with increasing dose of nickel and become significantly lower (P < 0.05) at higher concentration when compared with the control. Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were also lowered with concentration of toxicant when compared with the control. The results of the present study showed that a short-term exposures to high levels of nickel induced stress reactions in C. carpio. Some adaptive changes were observed; preparing the organism to an increased energy expense, whereas other changes showed a considerable immunosuppressive effect of stress. It was concluded that changes observed indicate that hematological parameters can be used as an indicator of Ni stress in C. carpio.