The effects of rearing conditions on hematology and susceptibility of common carp to experimental manipulation stress. The aim of present study was to compare hematological values in pond-reared and hatchery-reared common carp, and their hematological alterations following experimental manipulation. Two groups of carp: pond, and hatchery-reared juveniles were subjected to experimental manipulation -transfer of each fi sh for three hours to separate, aerated but confi ning aquaria. Blood was

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... led and hematological parameters were evaluated (erythrocyte and leukocyte counts, hemoglobin concentration, hematocrit, metabolic activity of phagocytes), and differential erythrocyte and leukocyte counts were calculated in the smears. Prior to stress, pond fi sh showed higher erythrocyte count and hemoglobin concentration, lower erythrocyte volume, and higher leukocyte count and phagocyte activity comparing to the hatchery fi sh. Reaction of both groups of fi sh to manipulation also differed. Pond fi sh showed erythrocyte swelling, and strong leukopenia (lymphopenia and neutropenia), and a decrease in phagocyte activity, while in hatchery fi sh increase in erythrocyte count and phagocyte activity took place. Rearing conditions signifi cantly affected hematological parameters of fi sh, pond-reared carp showing higher oxygen transport and immunological capacities comparing to the hatchery-reared ones. Pond fi sh showed also higher susceptibility to stress.