Abstract
<jats:p>The detected diversity in chars of the genus Salvelinus is largely determined by the correct differentiation of their intraspecific groups. The parasitological method allows assessing long-term food specialization in fish, and identifies ecologically homogeneous groups attributable to ecotypes, forms, and local populations. Aggregation of helminthes, based on a combination of species transmitted to fish through a certain group of invertebrates, can be used as effective bioindicator for differentiation of fish groups. The parasitological approach should not be considered as the only, independent and universal method determining the differentiation of fish groups. It ought to be supplemented with data from other methods of studying fish, at least with information about their current diet.</jats:p>