Introduction. Single intraperitoneal injections of sublethal doses of cadmium (10 µg Cd·kg-1 body weight) and nickel (60 µg Cd·kg-1 body weight) were administered to carp, Cyprinus carpio L., to determine detoxification potential of the fish affected after transfer to a clean milieu, as revealed by haematological parameters. Observation of haematological parameters allows the most rapid detection of changes in fish after cadmium and nickel injection Disrupted haematological patterns appear very quickly and precede changes in fish behaviour and visible lesions. The rapidity of toxic effects exerted by xenobiotics is related to the blood’s transport function, with the blood distributing the metals to all the body parts. Materials and methods. Each experiment took 60 days and was divided into 8 stages during which blood was collected for assays. At each stage, blood samples were assayed for selected haematological parameters (RBC, WBC, Hb, Hct, MCV, MCHC, MCH). Results. Cadmium and nickel exposure-related changes in haematological parameters were detected. Immediately after injection, the haematological parameters were seen to change, a return to the normal values being observed after some time. The study allowed following the changes in the haematological parameters of cadmium- and nickel-injected carp during the process ofdetoxification. Conclusion. Within the 60 days following injection of sublethal doses of cadmium and nickel, haematological parameters were observed to revert to the levels close to those in the control.

toxicity, fish, Cyprinus carpio, cadmium, nickel, RBC, WBC, Hb, Hct, leukogram, erythrocyte-related parameters