The fauna of char parasites of Baikalian mountains and peculiarities of their ecology in four mountain lakes of Transbaikalia are studied, including Frolikha Lake – the typical location of davatchan. The certain differences between populations in these lakes are revealed in species composition of parasites and in quantitative characteristics of fish infestation with parasites (first of all with Proteocephalus longicollis e Diphyllobothrium ditremum). This is due to specificity, pattern of origin of different lakes and composition of their ichthyofaunas. Frolikha Lake is dominated by fish of plain faunistic complex. The chars of this lake are the most different from chars of all other populations. Two chars assemblages which differ from each other in the level of consumption of plankton and benthos are registered in Bol'shoe Leprindo Lake. The chars of the first group are characterized by small indices of invasion with cestodes P. longicollis, the fish of the second group, unlike those of the first one, are heavily infected by this parasite. Our results show that chars from 4 surveyed lakes can experience considerable pressure of helminthes, which are pathogenic for these fish and can be one of regulators of their population density.