Seasonal depth distribution and thermal experience of the non-indigenous round goby Neogobius melanostomus in the Baltic Sea: implications to key trophic relations

Jane W Behrens,Ann-Britt Florin,Heli Einberg,Karin Hüssy,Patrick Polte,Elina Knospina,Didzis Ustups,Redik Eschbaum,Kristiina Nõomaa,Daniel Oesterwind,Mikael Van Deurs,Marie P Ryberg,Wlodzimierz Grygiel,Bastian Huwer,Szymon Smoliński,Henn Ojaveer,Jens Peter Herrmann

doi:10.1007/s10530-021-02662-w

Abstract

Native to the Ponto-Caspian region, the benthic round goby (Neogobius melanostomus) has invaded several European inland waterbodies as well as the North American Great Lakes and the Baltic Sea. The species is capable of reaching very high densities in the invaded ecosystems, with not only evidence for significant food-web effects on the native biota and habitats, but also negative implications to coastal fishers. Although generally considered a coastal species, it has been shown that round goby migrate to deeper areas of the Great Lakes and other inland lakes during the cold season. Such seasonal movements may create new spatio-temporal ecosystem consequences in invaded systems. To seek evidence for seasonal depth distribution in coastal marine habitats, we compiled all available catch data for round goby in the Baltic Sea since its invasion and until 2017. We furthermore related the depths at capture for each season with the ambient thermal environment. The round goby spend autumn and winter at significantly deeper and offshore areas compared to spring and summer months; few fish were captured at depths < 25 m in these colder months. Similarly, in spring and summer, round goby were not captured at depths > 25 m. The thermal conditions at which round goby were caught varied significantly between seasons, being on average 18.3 °C during summer, and dropping to a low 3.8 °C during winter months. Overall, the fish sought the depths within each season with the highest possible temperatures. The spatial distribution of the round goby substantially overlaps with that of its main and preferred prey (mussels) and with that of its competitor for food (flatfish), but only moderately with the coastal predatory fish (perch), indicating thereby very complex trophic interactions associated with this invasion. Further investigations should aim at quantifying the food web consequences and coupling effects between different habitats related to seasonal migrations of the round goby, both in terms of the species as a competitor, predator and prey.

Highlights

Migration is a common phenomenon within many taxa of animals, terrestrial as well as aquatic
Round goby is invasive on both sides of the Atlantic Ocean by occurring in high numbers in the North American Great Lakes, the Baltic Sea and several European inland waterbodies (Kornis et al 2012)
The depth at which round goby were caught varied significantly between quarters (p \ 0.001), except for Q2 and Q3, where fish were caught in shallow water of average depths of 9.4 and 8.2 m, respectively (Fig. 2a)

Summary

Introduction

Migration is a common phenomenon within many taxa of animals, terrestrial as well as aquatic. One way to define migration is as a synchronized, large-distance movement of a population between separate habitats, which usually occurs with a regular periodicity (Leggett 1977; Dingle and Drake 2007; Lucas and Baras 2001) Such spatial displacement, often of substantial biomasses may exert significant impact on community structure and function, flux of energy and nutrients between different areas and habitats, and on species interactions (Deegan 1993; Varpe et al 2005; Marczak et al 2007; Bauer and Hoye 2014; van Deurs et al 2016). To be able to evaluate the impact a non-native invasive species has on the invaded system, it is imperative to understand the species ecology, including migration patterns, for planning of any mitigation measures (Ojaveer et al, 2015)

Methods

Results

Conclusion