One hundred and forty-eight specimens of Prochilodus lineatus (Valenciennes, 1836) were collected on the Upper Paraná River floodplain, Brazil. Kritskyia boegeri presented significant differences in the abundance according to the host stage of gonadal maturity. Ergasilus sp. presented negative correlation between the GSR of the females and parasite abundance. K. boegeri presented negative correlation between the GSR of the males and abundance. Tereancistrum curimba and Saccocoelioides magnorchis occurred in higher abundance in the open lagoons. Rhinonastes pseudocapsaloideum and S. nanii presented higher abundance in the channels and Tylodelphis sp. presented higher abundance in the closed lagoons and in the rivers. K. boegeri and Amplexibranchius sp. presented significant differences in their abundances between the months of the year. Saccocoelioides nanii presented higher abundances in February-March 2000. Only Tylodelphys sp. presented correlation between fluviometric level and abundance and S. nanii presented significant correlation between water temperature and prevalence.
Prochilodus lineatus; parasite; Upper Paraná River floodplain; Brazil
