[Application of the dynamic phase portrait method for the analysis of structural transformations in the component parasite communities of the minnow Phoxinus phoxinus (L.)].

The present study aimed to investigate structural changes in communities of fish parasites by the method of dynamic phase portrait. This method allows revealing equilibrium states of communities and analyzing a response of community near and far from these states. Seasonal succession of the parasite communities in Phoxinus phoxinus of different age from the rivers Ulcheksha and Chovju is considered as an example. The obtained phase portrait were found to reflect the seasonal succession of the parasite communities whether the rate of different parasite species abundance was analyzed by the number or biomass. The process of forming was recorded in the studied parasite communities in May, while in June these communities come to the equilibrium state with maximum species diversity, minimum speed of the diversity's change, and considerable quantity of parasites. However, this equilibrium state is unstable. Interpopulation connections lead to further structural transformations, and at the end of July-the beginning of August, when the above parameters have minimal values, the community comes to a new equilibrium state. Later on, in August-September, when the host fish is invading by a new generation of parasites, the community comes out the equilibrium state. Unlike the parasite communities in the host of age 1+-3+, the community in Phoxinus phoxinus 0+ begins to form in July. Diversity index of such community is lesser.