Length-weight relationship of Ligula intestinalis plerocercoids in adult silver bream and discussion on estimation of the parasite age.

The paper comprises an evaluation of Ligula intestinalis infection in adult silver bream (Blicca bjoerkna), from the Nové Mlýny Reservoirs (Czech Republic), from 1991 to 1993. The prevalence (mean 4.39%) and intensity (mean 1.39 spec.) of infection were very low, ranging from 1.48% (1.11 spec.) in April-May to 11.52% (1.36 spec.) in November-December. The length-weight relationship of single infection plerocercoids was characterized by the regression and correlation coefficients of linear and exponential regressions. The lowest weight and mean lengths of plerocercoids were found in April-May. According to the length and weight of plerocercoids in our collection those specimens were preliminary separated into 0+ to 5+ age classes. It is supposed that the longevity of the longest specimens of L. intestinalis plerocercoids attain the same age as their intermediate host (silver bream). The longest plerocercoid attained the body length of 1,006 mm and the weight of 32.0 g.