EN
In the rudd aged two years and infected with Ligula intestinalis plerocercoids the relation between its body weight and lenght (longitudo corporis) was described as W=0.0129xL. The analogous relationship in healthy fish was W=0.0166xLAt a relative infection intensity of 7.99 per cent, the infected fish were about 29.5 per cent lighter than the healthy ones. The difference between the mean body length of infected and healthy fish was not significant (p<0.05). The infection occured mainly in early spring. Plerocercoids showed a regular increase of weight during the year. An average infection extensiveness was 31.6 per cent and it underwent seasonal changes with vertices in early summer and autumn. Fish infected with more than one plerocercoid displayed an increased death rate in summer months.