Karlson, A. M. L., Almqvist, G., Skóra, K. E., and Appelberg, M. 2007. Indications of competition between non-indigenous round goby and native flounder in the Baltic Sea. – ICES Journal of Marine Science, 64: 479–486. The Ponto-Caspian round goby (Neogobius melanostomus) was introduced to the Gulf of Gdańsk, southern Baltic Sea, in the late 1980s, and it has now become the dominant demersal fish species in shallow water. This study aimed to assess diet preferences and the degree of diet overlap between the round goby and the native flounder (Platichthys flesus). Results from time-series of stomach contents and stable isotope analyses of wild-caught fish, together with prey preference experiments carried out in the laboratory, showed that the two species consumed similar species and sizes of prey. The similarities in diet suggest potential for food competition. Catch data showed both reverse depth distributions of round goby and flounder when round gobies were abundant and that the abundances of the two species were negatively correlated. The diet overlap between small flounders and round gobies was greatest when goby abundance was least, suggesting that abundance of round gobies may restrict flounder habitat utilization and, therefore, also food availability to the latter. Therefore, round gobies may have a negative influence on the commercially important flounder.

The Ponto-Caspian round goby (Neogobius

No abstract

We analysed the pattern of genetic differentiation among six newly established (around 10 generations) sites of the round goby (Neogobius melanostomus) in the southern Baltic Sea by means of nine microsatellite loci and in total 183 individuals. All but one site were within 30 km from each other. We found statistically significant genetic differentiation in ten out of 15 comparisons after Bonferroni correction, and since the species is newly introduced this has happened in less than ten generations. The largest genetic differentiation was found between the two most divergent habitats, while sites with a similar habitat were not significantly differentiated. Estimates of gene flow (Nm) were low and ranged from 1.5 to 5.5. A large proportion of individuals were assigned to one site (Puck), suggesting that this site has acted as a source to the other sites.