Feeding ecology, growth and reproductive biology of round goby Neogobius melanostomus (Pallas, 1814) in the brackish Kiel Canal

We studied diet, growth and reproductive biology of round goby Neogobius melanostomus from the Kiel Canal, northern Germany, to give an insight into the life cycle of this species in a brackish water canal. Crustaceans had the highest importance in the diet of all examined size classes of round goby. Other major food taxa were annelids and chironomids. Mussels and fish were consumed almost exclusively by medium- and large-sized N. melanostomus and contributed to the diet to a minor extent. In addition to the variability between size classes, we found a high interannual variability in the prey species. Round goby in the Kiel Canal was characterised by relatively low asymptotic total length and high relative fecundity. An almost balanced sex ratio indicates the established status of the population. The highest spawning activity took place between May and the end of June. From our data, negative effects of round goby on native species due to competition for prey and habitat are more likely than due to direct predation on eggs or fry. Affected species with similar habitat requirements are for example small gobiids from the genus Pomatoschistus. As round goby occurs in high abundance, substantial changes of the Kiel Canal ecosystem seem possible and likely.