[Parasitic protozoa of the bream (Abramis brama L.) in the Rybinsk reservoir].

The fauna of parasitic protozoans of the bream (Abramis brama) from different reachs of the Rybinsk water reservoir was investigated. 350 fish specimens have been examined by the method of total dissection. The greater number of parasites and diversity (33 species) were observed in the Volzhski reach: infusoria--16 species, myxosporidia 12, flagellata--4, dermocystidia--1. In the breams of Sheksninski reach 18 species of parasites were recovered: infusoria--8, myxosporidia--8, flagellata--1, dermocystidia--1. Parasite protozoans from the Molozhski reach were represented by 14 species: myxosporidia--8, infusoria--5, flagellata--1. Statistic analysis of the morphological variability of spores of the myxosporidians from gills (Myxobolus muelleri and M. exiguus) has displayed the decrease of spore size in the row Molozhski-Volzhski-Sheksninski reachs. Some parasitic protozoans could be used as indicators of local fish herds.