EN
The total number of examined sheatfishes derived from Biebrza river was 151, the over-all infestation amounted to 69.3%. Among the 14 species of detected intestinal parasites (table) three: Silirotaenia siluri (Batsch, 1786), Rhabdochona denudata (Dujardin, 1845) and Orientocreadium siluri (Bychowsky et Dubinina, 1954) were new ones for Poland. The examination was also concerned with the correlation between the parasitic fauna of sheatfish and its victim - burbot (Lota lota). The incidence of Ergasilus sie boldi Nordm. and Piscicola geometra (L.) in sheatffsh was an additional finding.