Abstract
Haematological studies of Cyprinus carpio in the present work include the erythrocyte count, haemoglobin concentration and haematocrit value or packed cell volume of blood, and subsequently absolute values of M.C.V., M.C.H. and MCHC were calculated by the respective formulae. The major effects of nickel on the blood parameters are concerned with total count of RBC, their size and differential count of WBC. The significance of the present study is concerned with metallic pollution of major rivers of Jharkhand state.