Increasing Population of the Invader Round Goby, <I>Neogobius Melanostomus</I> (Actinopterygii: Perciformes: Gobiidae), and its Trophic Role in the Curonian Lagoon, Se Baltic Sea

Abstract

Background. The round goby, Neogobius melanostomus (Pallas, 1814), is a recent invader in the Curonian Lagoon, SE Baltic Sea. As invasive species are among the most severe threats for biodiversity loss and can induce food web alterations, the development of round goby population in the Curonian Lagoon and its possible impacts on fish community and the entire ecosystem are of great scientific interest. This research reports on the expansion and trophic role of round goby in the Curonian Lagoon. Materials and methods. Occurrence and abundance of round goby was investigated using a beach seine and gill nets at the northern and central parts of the Curonian Lagoon during a six-year period from 2007 to 2012. The trophic niche of the newcomer was revealed by applying gut content and stable isotope analyses (SIA). A total of 61 samples of other fish species were taken for SIA in order to reveal with which resident fish species the exploitative competition could be expected. Stable isotope mixing models were used to evaluate the contribution of round goby to the nutrition of top predators of the Curonian Lagoon: European perch, Perca fluviatilis Linnaeus, 1758; pike-perch, Sander lucioperca (Linnaeus, 1758); great cormorant, Phalacrocorax carbo; and grey heron, Ardea cinerea. Results. The survey showed that round goby expanded its distribution area and recently occurs in the entire Lithuanian part of the Curonian Lagoon. Variation in the density of round goby suggests that the invader's abundance may be stabilised in the northern part of the lagoon. Gut content and stable isotope analyses showed round goby being mainly benthivorous. The largest trophic overlap with respect to SIA was detected between the invader and ruffe, Gymnocephalus cernua (Linnaeus, 1758), the fish which presumably exploits the same habitat type. According to stable isotope mixing models round goby was included with considerable shares into the diet of top predators. Conclusion. The further expansion of round goby inside the Curonian Lagoon is ongoing. However, there is evidence on population density stabilisation in the northern part of the lagoon. Native benthivorous fish, especially ruffe, may be affected through competition for food resources in habitats where the newcomer is numerous. Round goby significantly contributes to the diet of piscivorous fish and birds. That may promote the regulation of invader population abundance in the lagoon.

Diet overlap between juvenile flatfish and the invasive round goby in the central Baltic Sea

“…Assuming that the round goby in the area originates from the Lithuanian population or the Liepaja harbour area, the approximate dispersal rate of round gobies can be estimated to have been approximately 7 km per year. This dispersal rate is similar to that observed in the Curonian Lagoon, Lithuania (Rakauskas et al, 2013).…”

Predator and prey: the role of the round gobyNeogobius melanostomusin the western Baltic

“…In the Baltic Sea, round gobies were first caught in the Gulf of Gdansk in 1990 and had become one of the dominant species in the western part of the Gulf by 1999 (Sapota & Skóra 2005). The invasion expanded in a northeasterly direction towards the Curonian Lagoon (Rakauskas et al 2013), the Gulf of Riga and the Gulf of Finland (Ojaveer 2006), as well as in a westerly direction (Winkler et al 2000;Winkler 2006;Czugała & Woźniczka 2010;Schomaker & Wolter 2014). While several studies about the invasive process in the Great Lakes were published within recent decades (e.g.…”

Infection rates and prevalence of metazoan parasites of the non-native round goby (Neogobius melanostomus) in the Baltic Sea

“…Cormorants have been known to prey actively on round gobies where they co-occur, e.g. in the Gulf of Gdansk (Bzoma, 1998) and the Curonian Lagoon (Rakauskas et al, 2013). Thus, round goby is a potential paratenic host in completing the life cycle of this C. rudolphii in the Danish and Lithuanian populations (Table 4).…”

“…However, since the diet of the round goby has been shown to vary both seasonally and between size groups (e.g. Skora & Rzeznik, 2001;Rakauskas et al, 2008Rakauskas et al, , 2013Brandner et al, 2013b;Ustups et al, 2015), future parasitological studies should investigate both seasonal and size-related differences in the infection rates of the round goby in the Baltic Sea.…”

“…Following its initial detection in the Gulf of Gdansk in 1990 (Skora & Stolarski, 1993), it spread throughout the southern Baltic Sea, eastward to the Vistula lagoon and river system (Mierzejewska et al, 2011), westward to the German and Danish coastal areas and further north along the southeastern coast of Sweden (Florin & Karlsson, 2011;Sapota, 2011). In the northern parts of the Baltic Sea, round goby became a permanent component of the Lithuanian, Latvian and Estonian coastal fish fauna in the 2000s (Ojaveer, 2006;Sapota, 2011;Rakauskas et al, 2013;Strake et al, 2013). By 2011, the species had been recorded along the Finnish coast of the Gulf of Finland, in the Archipelago Sea and the Å land Islands.…”