The purpose of research is to develop a simulation model of natural and technical systems for small and medium-sized rivers management, taking into account the requirements of fisheries. Natural and technical systems of minor and medium-sized rivers include the catchment area, river channel and its tributaries, a complex of hydraulic structures, sectoral structures (intakes, bridges, and crossings), ponds, water protection and special fishery facilities. Such natural and technical systems belong to the complex systems according to the composition of its components, so system analysis and simulation modeling are the most effective research methods of their parameters optimization. The developed simulation model is based on the current data on the minor and medium rivers pools and is aimed at optimizing the parameters of its natural and technical systems with the aim of increasing the efficiency of natural reproduction of anadromous species of fish. Using the developed model requirement estimation in artificial spawning grounds for the river Kundryuchey was done, where the graving riffles with a stone and pebbles substrate suitable for spawning are in the area 6 to 53 km from the mouth. It is established that the existing spawning grounds from the mouth of the river up to 28 km are not sufficient for effective natural reproduction of anadromous fish, and they exceed the requirements beyond this area. Thus, to improve the efficiency of reproduction of anadromous fish in the river Kundryuchey 0.43 hectares artificial spawning must be placed on river stretch from the mouth up to 28 km.
Keywords: natural-technical system, management, simulation model, hydrological regime modeling, fisheries releases.
