Abstract
The paper considers the ecological variability of the round goby, Neogobius melanostomus (Pall.), in different environments. The dietary spectrum and morphological variability of round goby populations were studied in two water bodies with different environmental conditions. The sizes and body weights of specimens were the largest in Obytichna Bay and the smallest in Kakhovka Reservoir. Differences in the morphological indices of gobies from freshwater and marine bodies of water were determined using discriminant analysis. At the study sites the round goby chiefly fed on benthic organisms that varied in species composition and energy equivalent. A significant portion of the diet comprised bivalves such as Abra ovata, Cerastoderma glaucum, and Parvicardium exiguum, which have the highest energy capacity. The average energy equivalent indices of prey items were higher in Obytichna Bay and the lowest in Kakhovka Reservoir.