Do invasive bighead gobyNeogobius kessleriand round gobyN. melanostomus(Teleostei, Gobiidae) compete for food?

Abstract

Bighead goby (Neogobius kessleri ) and round goby (Neogobius melanostomus ) have been invading new non-native areas about two decades successfully. In this study, diet spectrum, seasonal variation, feeding strategy and diet overlap between these two invasive species were assessed. Materials were collected from the Danube at Bratislava by fishing rods and/or electrofishing. The diet spectrum of both species was diverse: a total of 46 food types in bighead goby and 51food types in round goby were observed. Dikerogammarus sp., chironomid larvae and Corophium sp. were the most predominant food types in bighead goby, whereas in round goby, chironomid larvae, Corophium sp., bryozoans and Cladocera predominated. The diet varied over seasons. In the Slovak part of the Danube, bighead goby and round goby have adapted to local food resources, consuming diverse food from small to large items, both with soft and/or hard body. This enhances the capability of these invasive species to spread successfully. It appears that even if both exploit similar food resources, their proportional content differs. Further differences between these gobies were also found in their food behaviour and feeding strategy. Both species tend to be specialists where possible, but round goby demonstrates higher flexibility towards general feeding strategy.