Modelling of white bream (Blicca bjoerkna (Linnaeus, 1758)) commercial catches by different parameters of fishing gillnets in Kyiv Reservoir

Purpose. To analyze the existing experience in quantitative and qualitative modelling of commercial fish harvesting and to develop the methodological approaches in determining the optimal catch parameters for gillnets. Methodology. An adjusted annual commercial mortality rate was used to determine the catches composition in gillnets with different mesh sizes. Findings. The proposed model was developed within the framework of the generally accepted concept of population dynamics and biomass as a result of mortality and weight growth. It showed the dependence of the size-age structure and total weight of the catch on the mesh size of the grids. Originality of the work was caused by using the mathematical model that can ensure sustainable use of nature based on the optimal parameters of shutter grids on the possibility of their effective removal of certain age groups of white bream for the first time. Practical Value: calculations performed according to this model for the white bream of the Kyiv Reservoir showed that it is optimal to use grids with a mesh step of 40-50 mm, which allow to obtain the maximum catch per unit of replenishment and ensure high population fertility.