A laboratory study of potential effects of the invasive round goby on nearshore fauna of the Baltic Sea

摘要

In the Baltic Sea, species diversity is relatively low and the introduction of new predator species can have large direct and indirect impacts on native species – both prey and potential competitors. The alien round goby Neogobius melanostomus Pallas, 1811 was introduced to the Baltic Sea in the early 1990s and is now well-established. We examined the feeding habits of male round gobies from the ?land Islands, Finland, where round gobies were first recorded in 2011. Specifically, we tested whether small round gobies (165 mm TL) showed size and/or species preferences (using Manly’s selectivity index) for two abundant bivalve prey items, the blue mussel Mytilus trossulus Gould, 1850 and the Baltic clam Macoma balthica Linnaeus, 1758. When offered two sizes of clams, small round gobies did not show a prey preference. When offered two sizes of mussels, round gobies selected for small mussels (6 – 9 mm) and against large (10 – 13 mm) mussels. When offered both bivalve species and sizes simultaneously (four prey options), round gobies selected for small blue mussels and against large clams. Combined, these results suggest that small round gobies will selectively feed on the preferred prey if available and if not, their feeding will reflect the availability of various prey items in the environment. In addition, round gobies consumed small ( 38 mm TL) individuals of the native flounder Platichthys flesus Linnaeus, 1758. Round goby and flounder have the potential to overlap in habitat use and previous literature has suggested a diet overlap between the two; however, this is the first evidence of direct predation on flounder by round gobies.