Annual changes in hematological parameters of common carp juveniles under laboratory conditions

Annual changes in hematological parameters of common carp juveniles under laboratory conditions. The aim of the study was to evaluate the changes of the values of hematological parameters of carp juveniles in annual cycle under stable laboratory conditions. Some parameters showed distinct rhythms of changes, e.g. 2 peaks of hematocrit occurred in II and VIII, of hemoglobin concentration in I and VI, while erythrocyte count showed maximum in II. The largest erythrocytes were observed in VIII, and the smallest in XII. Leukocyte count showed two peaks in XII and III. Maximum lymphocyte frequency occurred in III and minimum in XI, while percentage of neutrophils showed the reverse pattern. Oxidative metabolic activity of phagocytes peaked in III, while minimum occurred in XI–XII and VI–VII. Thrombocyte count was highest in XII, and lowest in VII. The obtained results revealed that the values of hematological parameters in carp considerably changed during the year despite little alterations in environmental factors. Some of these changes, e.g. increase in oxidative activity of phagocytes in spring and increase in hemoglobin level in summer were similar to those that occur in fi sh under natural conditions. Another changes, such as increase in erythrocyte size or decrease in leukocyte count suggest long-term adjustment to the laboratory environment.