[Long-period endogenous oscillations in fish population size: mathematical modeling].

We present a mathematical model of an aquatic community, where the size-and-age structure of hydrobiont populations is taken into account and the corresponding trophic interactions between zooplankton, peaceful fish and predatory fish are described. We show that the interactions between separate components of the aquatic community can lead to long-period oscillations in fish population size. The period of these oscillations is of the order of dozen years. With the use of the model we show also that an increase in the zooplankton growth rate can be followed by a set of the fish population dynamical bifurcations: stationary states --> regular oscillations --> quasicycles --> the dynamical chaos.