Invasive gobies in the Danube: invasion success facilitated by availability and selection of superior food resources

Abstract

We investigated somatic condition, growth rate, diet and food resources of the native (lower Danube) and non-native (upper Danube) populations of invasive bighead goby Neogobius kessleri and round goby N. melanostomus within the Danube River to answer the question whether prey availability and type may have facilitated successful goby invasion to the upper Danube. The non-native populations of both species were in better somatic condition and grew faster. The biomass of nonmollusc macrozoobenthos, dominated by Amphipoda, was markedly higher in the non-native range while molluscs were recorded frequently in both the native and non-native ranges. Amphipods were far the most consumed prey by nonnative fish, whereas native fish combined two main prey types -amphipods and fish (bighead goby) and amphipods and bivalves (round goby). A laboratory experiment was conducted to reveal whether the low consumption of bivalves by the round goby in the non-native range reflects prey encounter rates or alternatively prey selectivity. When bivalves and amphipods were offered simultaneously in excess to the experimental fish, round goby showed strong preference towards amphipods. Molluscs are hypothesised to be an alternative rather than the most preferred prey for the round goby. Rich food resources utilised by the non-native bighead and round goby contribute to their invasive success in the upper Danube.

Life-history traits of non-native freshwater fish invaders differentiate them from natives in the Central European bioregion

“…Furthermore, all species that have established selfsustaining populations in Central European inland waters are known to have other relevant characteristics, usually attributed to successful fish invaders (Garcia-Berthou 2007). A broad diet, as well as an opportunistic feeding strategy were found in the racer goby, monkey goby, round goby and Amur sleeper in the invaded waters of Central European waters (Kostrzewa and Grabowski 2003;Grabowska and Grabowski 2005;Kakareko et al 2005;Borza and Eros 2009;Grabowska et al 2009a, b;Polačik et al 2009;Brandner et al 2013a). High environmental tolerance also characterizes most of these species, e.g.…”

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

“…was probably absent, the diet of bighead goby consisted mainly of trichopteran larvae and Corophium curvispinum (Adámek et al, 2007). Flexibility was also observed elsewhere in the River Danube, where the diet of invasive bighead goby differed between populations from native and non-native areas (Polačik, 2009). …”

“…Bighead goby and round goby are now very abundant, which implies that they could play an important role in foodweb interactions in the River Danube. A few studies devoted to diet of invasive populations of bighead goby and/or round goby have brought some basic information on the species diet composition (Simonović et al, 2001;Adámek et al, 2007;Copp et al, 2008;Polačik, 2009), some of them being more comprehensive, analysing seasonal and habitat variation (Borza et al, 2009). However, none of these papers provide a complex insight into the diet niche of these successful invaders.…”

Round goby predation onDreissenain coastal areas of eastern Lake Michigan

“…Although round goby diets were dominated by non-mussel invertebrates (mainly dipteran larvae and zooplankton) in coastal lakes connecting to Lake Michigan (Cooper et al 2009), Dreissena are likely an important component of the diets of round gobies inhabiting areas with hard substrates in coastal lakes (e.g., riprap in channels connecting coastal lakes to Lake Michigan; Ruetz et al 2009). Round goby often prefer non-mussel invertebrates over Dreissena in laboratory experiments (Diggins et al 2002;Bauer et al 2007;Polacˇik et al 2009;Coulter et al 2011), suggesting that densities of non-mussel invertebrates in the littoral habitats also could be an important predictor of the strength of predation by the round goby on Dreissena.…”