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

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.

Combined tracers reveal the multi‐dimensionality of resource partitioning among sympatric forage fish

“…During these months, the diet of round goby in Lake Ontario are dominated by dreissenid mussels and growth rates are also predicted to be highest across the annual growing season (Brush et al, 2012; Lee & Johnson, 2005). This contrasts with the autumn–winter period, when round goby migrate offshore to seek the warmest available habitat as represented by the 0–4°C waters the occur at depth during winter stratification (Behrens et al, 2022; Pennuto et al, 2021). Such a seasonal contrast in behavioural thermoregulation can also result in a 5–6‐fold decline in metabolism and bioenergetic performance (Skazkina & Kostyuchenko, 1968).…”

“…Subsequently, for δ 13 C and δ 15 N, consumer values may be obfuscated by short‐term changes in habitat and prey resource availability and subsequent exploitation behaviours that are not fully integrated by isotopic turnover kinetics. For example, in the spring–summer months, round goby select nearshore habitats that provide water temperatures approaching the preferred optimum (Behrens et al, 2022; Pennuto et al, 2021). During these months, the diet of round goby in Lake Ontario are dominated by dreissenid mussels and growth rates are also predicted to be highest across the annual growing season (Brush et al, 2012; Lee & Johnson, 2005).…”

Differential habitat use of a notorious invasive fish, the round goby, in a translocation‐relevant system

“…Increasing similarity of the respective trophic niches may be due to a higher mobility of round gobies, and migration from the walls to the bottom after the reproductive season. In lake and sea habitats, round gobies migrate to deeper waters (up to >70 m) in winter (Behrens et al, 2021; Carlson et al, 2021). While we do not know if comparable processes happen in rivers of relatively shallow depths (river Rhine in Basel, Switzerland: ca.…”

“…The proportion of sneaker males in a population can vary widely, with values between 4% (Cerwenka et al, 2020) and 40% (Bleeker et al, 2017) reported in different ecosystems. Outside of the reproductive season, they show higher mobility, or even migration patterns to deeper waters (Behrens et al, 2021; Carlson et al, 2021).…”

“…Round gobies occupy small home ranges (5 ± 1.2 m 2 , Ray & Corkum, 2001) in shallow waters during the reproductive season (April–September in their native range, Kornis et al, 2012). In the winter months after the reproductive season, they migrate to deeper waters in lentic and marine systems (Behrens et al, 2021; Carlson et al, 2021).…”