| Резюме: |
The dissertation covers the invasive potential of a fish called the round goby (Neogobius melanostomus). This study is focused on the invasion front of this species in the Danube tributaries of Bulgaria. For the last five years the round goby has expanded its range in several Danube tributaries. The individuals inhabiting these rivers are small-sized, with a narrow mouth, large ventral sucker, large eyes and narrow heads in comparison to those from the Danube River, the Black Sea or the Baltic Sea. Similarities in the outer morphology where observed between the Danube tributaries populations with those inhabiting the Great Lakes Basin (North America). Reproductive characteristics and feeding ecology traits of the studied populations contributed to the invasive potential of the round goby. Individuals inhabiting the Danube tributaries matured earlier, while their food niche was broad and diverse. The predominant feeding strategy was generalism. Negative impacts of the round goby on the native fish fauna were observed. After conducting a risk assessment protocol the species was evaluated as a high risk invasive species.
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