Health Status of the Nase (Chondrostoma nasus) in Breeding Farms from the Jihlava River Basin
This study compares two fish farms in the Jihlava River basin that differ mainly in the intensity of rearing of the nase fry and in water sources. During rearing, we observed the health condition of fry from hatching to expedition at the age of one year. Four species of parasites (i.e., Ambiphrya ameiuri, Apiosoma piscicolum, Trichodina sp., Diplostomum spathaceum) were found to infest the fish and Aeromonas hydrophila was isolated by bacterial culture. In both breeding facilities the intensity and prevalence of Ambiphrya ameiuri increased during the summer. The state of health and its development including the recognised infections was similar in both farms. Immunological indicators such as differential white cell count, absolute white cell count and the oxidative burst in autumn were evaluated in the fry samples. Although fry from both farms had similar health condition, the results on immunological indicators show that fry from farm I are more exposed to the effects of stressors. In the next phase, we confronted immunological indicators of fry from farm II and brood fish from the Jihlava River. The results show differences in immunological indicators, which could be caused by a variety of stress factors having different effects on the immune system of these two fish categories. The environment affects greatly the immunity of juvenile as well as brood fish. It reflects in the different levels of immunological indicators in the comparison of fry from two farms as well as in the comparison of fry and brood fish from the river.