[Component communities of the parasites of gudgeon (Gobio gobio) from the basins of Northern Dvina and Mezen rivers].

Component communities of parasites of gudgeon from the ecologically sustainable reservoirs are studied. The general principle of their organization is established. The material had been collected in the basins of Northern Dvina (41 specimens of gudgeon were dissected) and Mezen (55 specimens of gudgeon were dissected) rivers using generally accepted methods. Errors of regression equations for all individual species groups with their subsequent summation were calculate in order to estimate the state of the component community structure. In different seasons of a year the component community of the parasites of gudgeon from the Ertom river has the same structure, which is determined by the ratio of the biomasses of its comprising species, while it is differs in its species composition, biomasses of the species, leading groups of parasites, and in the dominating species. Thus, several stable seasonal states of the communities of fish parasites can be supposed. Three groups of species distinguished by the ratio of their biomasses are the general for the component communities of the parasites of gudgeon from the basins of Northern Dvina and Mezen rivers. The generalist species is more frequently the dominating species. The group of autogenic species always leads in the community. When methods of parasites collection are violated, the decrease in the number of species groups down to two is recorded. When the materials collected in different periods of a year from an ecologically sustainable reservoir are mixed, the sum of the errors of regression equations become higher than 0.250.