Seasonal changes in hematological parameters of Catla catla (Hamilton 1822)

Hematological parameters are repeatedly used as an essential diagnostic tool to assess the health condition of fish. The purpose of this study was to assess the reference values of some hematological parameters of Catla, Catla catla collected from a freshwater pond in a tropical climate of India from July 2008 to June 2010. Variations in hematological parameters such as hemoglobin, erythrocyte count, total leucocyte count, hematocrit, mean corpuscular volume (MCV), and mean corpuscular hemoglobin concentration (MCHC) of fish were compared according to sex and seasonal differences. Analysis of variance showed that there were significant differences between sexes and the results indicated that blood parameters levels between the sexes in summer were significantly different than that measure in other seasons except mean corpuscular hemoglobin (MCH) and MCHC value (P < 0.05). The number of total leukocyte levels was found to be higher in female fish especially in reproductive seasons, but the levels of hemoglobin, hematocrit, and MCV values were high in male fish in an annual period. However, there was no difference in MCH and MCHC values between the sexes and seasons throughout the study period. These may be related to season of sampling and changing physiological cycles during these months. The correlations between measured hematological parameters were also determined.