Distribution of Common Chub, Common Dace and Roach Across Environmental Gradients on the East Edge of Europe

The probability of occurrence, optimums, niche breadth, and distribution of three fish species in 559 small rivers on the eastern edge of Europe were studied. Roach was the most abundant species, while common chub was the most frequent by occurrence. The probability of occurrence of common chub, common dace, and roach differs significantly between our studies in the extreme east of Europe and those in river basins in the west of the continent. Cohabitation of all three species was noted in 13.1% of rivers. The highest percentage (22.9%) of cohabited fish was observed for chub and dace. Elevation and river depth were the main environmental factors influencing the distribution of all the selected fish species. Our research on the eastern edge of Europe shows that fish niche widths can vary significantly between species for some environmental factors, while being similar for others.