Does the site of blood collection and sex of crucian carp (Carassius carassius) affect hematological and blood biochemical results?

Blood analysis is used to evaluate the effects of various environmental factors on fishes and to assess fish health and welfare. Fish blood is routinely sampled from the caudal vein or the heart. The aim of the present study was to determine the differences between venous and cardiac crucian carp (Carassius carassius (L.)) blood parameters. Additionally, the influence of sex was tested. The fish were divided into two groups: group I consisted of 10 males and 9 females, group II consisted of 8 males and 8 females. The fish from group I had blood sampled first from the caudal vein and then from the heart. The fish from group II had the procedures in the opposite order. The hematological parameters determined in the present study depended on the blood collection site and the sex of the individuals. Blood biochemical indices depended on the sex of the fish but not on the blood sampling site. The effect of sampling order was observed in the case of both hematological and biochemical parameters. The results of the current study indicated that the blood collection site, the sex of fish, and sampling order should be taken into consideration in hematological experiments.