Tubenose goby Proterorhinus marmoratus ( Pallas , 1814 ) has joined three other Ponto-Caspian gobies in the Vistula River ( Poland )

The Ponto-Caspian fish species, tubenose goby Protherorhinus marmoratus, was recorded for the first time in Poland. Six specimens were captured during April 2008 from rip-rap habitat where the river enters of Włocławski Reservoir, which is situated in the lower section of the Vistula River (Baltic basin). This appears to be the next stage in the species’ westward invasion through the so-called ‘central invasion corridor’ for Ponto-Caspian species. The tubenose goby is, therefore, the fourth alien goby in recent decades to disperse into Polish inland waters, following after the round goby Neogobius melanostomus, the racer goby Neogobius gymnotrachelus and the monkey goby Neogobius fluviatilis.

The Ponto-Caspian region is thought to be one of the major donor areas for alien aquatic species, both in central Europe (bij de Vaate et al. 2002) and North America (Ricciardi and MacIsaac 2000).The invasion of North American waters by Ponto-Caspian species resulted from releases of ballast waters from transoceanic ships, whereas the migration of aquatic invertebrates and fish from the basins of Black, Azov and Caspian seas into the Baltic and North Sea basins has followed the three invasion corridors described by bij de Vaate et al. (2002).Amongst the most impressive of the East-to-West expansions in the recent decades have been those of the gobies (Copp et al. 2005).Until now, only three species of Ponto-Caspian gobies have been recorded in Poland: round goby Neogobius melanostomus (Pallas, 1814) (Figure 1), racer goby Neogobius gymnotrachelus (Kessler, 1857) (Figure 2) and monkey goby Neogobius fluviatilis (Pallas, 1814) (Figure 3).
The round goby was first time reported in 1990 in Puck Bay, Gulf of Gdańsk, Baltic Sea (Skóra and Stolarski 1993).It soon spread along the entire Polish part of the Baltic coast, colonized some coastal lakes and the Vistula Lagoon and invaded other parts in the Baltic i.e. coast of Germany (Corkum et al. 2004), Estonia, Finland, Lithuania (Ojaveer 2006).Since 2004 it is present also in the North Sea basin (Netherlands) (van Beek 2006).Round goby became one of the dominant species in the Gulf of Gdańsk, especially in the shallows (Sapota 2004), and began moving up the Vistula River and by 2002 was found as far as 130 km upstream of the river's mouth (Kostrzewa et al. 2004) (Figure 4).
The most probable route of the round goby's arrival in the Gulf of Gdańsk was via the socalled northern corridor, which consists of the Volga River, the Rybinsky Reservoir, and the Ladoga and Onega lakes, which are connected to the Gulf of Finland by artificial canals (Sapota 2004).Its introduction to Polish waters is often attributed to ballast-water transport (some types of ships i.e. 'Volgo-Balt' use ballast waters and   not only sail between the Black Sea and the Baltic but also move upstream big European rivers) but gobies are able to disperse also by 'hitch-hiking' as eggs attached to the river vessels (Wiesner 2005).Two other gobies species (racer, monkey) have invaded the Baltic basin via the central corridor, which follows the rivers Dnieper (Gulugin and Kunitsky 1999) and Pripyat (Black Sea basin) through the Pripyat-Bug canal to the rivers Bug (also known also as the Western Bug) and Vistula.The racer goby was first reported in Poland when specimens were found in 1995 in the middle course of the Bug River in the vicinity of Pripyat-Bug connection (Danilkiewicz 1996).Two years later, monkey goby was found in virtually the same section of the Bug River (Danilkiewicz 1998).Both species rapidly expanded in the entire Polish part of the Bug River and invaded the lower stretch of the Vistula, almost to the river mouth (Kostrzewa et al. 2004) (Figure 4).Based on mitochondrial DNA analysis of racer goby (Ohayon and Stepien 2007), the Dnieper River has been identified as the most likely origin of racer goby found in the Vistula basin.
In April 2008, the fourth species tubenose goby Proterorhinus marmoratus (Figure 5) was recorded for the first time in Poland.Six individuals (five females and one male) of tubenose goby (total length 52-58 mm) were found in the Vistula River near the bridge at Płock (52°32'05"N, 19°41'12"E) at the downstream end of the Włocławski Reservoir).The fish were caught by electrofishing at depths from 0.2 to 0.5 m along the rip-rap of river banks devoid of vegetation, which resembles the habitat described for racer goby invading the middle stretches of the Danube River (Ahnelt et al. 1998;Prášek and Jurajda 2005;Wiesner 2005).Also captured were racer goby (dominant in abundance), monkey goby and single specimens of native species i.e. roach (Rutilus rutilus (Linnaeus, 1758)), three-spine stickleback (Gasterosteus aculeatus Linnaeus, 1758).
Tubenose goby was reported in August 2007 for the first time in the upper and middle parts of the Pripyat River (Belarus), very close to the Pripyat-Bug canal (Rizevsky et al. 2007), which suggests that the species reached Poland and the Vistula basin via the Pripyat-Bug canal.Tubenose goby was not found during surveys conducted in the Bug River in August 2007, when a total of 197 racer goby and 319 ones of monkey goby were captured at 20 sampling sites situated approximately every 10 km from the vicinity of the Pripyat-Bug connection to the confluence with the Vistula (Grabowska et al.upublished data).The site where tubenose goby was first recorded in Poland is about 405 km downstream of the confluence of the Bug River with the Pripyat-Bug connection.Such 'jumps' in distribution by gobies invading the Danube basin have been attributed to 'hitch hiking' on  river ships (Ahnelt et al. 1998;Wiesner 2005), however the Bug River is almost never used as a waterway for ships or barges.This suggests that tubenose goby is expanding rapidly by natural dispersal, and the species is therefore likely to invade most of the Vistula river Basin within a short time.
The natural distributions in freshwaters of most euryhaline Ponto-Caspian gobies were limited mainly to brackish lagoons of the Black, Azov and Caspian seas and lower reaches of their rivers.Therefore, the tubenose goby may be considered as having the greatest natural range among them, with presumably the best ability to establish truly riverine populations.This appears to be the case for the upstream stretches of the Danube basin (Ahnelt et al. 1998;Prášek and Jurajda 2005) and in the rivers Dnieper, Don and Volga (Naseka et al. 2005).The tubenose goby has also reached to the lower parts of the Rhine catchment via the Rhine-Main-Danube waterway (e.g.von Landwűst 2006).Recently it was found in the lower section of Neva River and in the eastern part of Gulf of Finland (Antsulevich 2007) spreading there probably through the Volga-Baltic inland waterway (i.e. the northern corridor sensu bij de Vaate et al. 2002).Tubenose goby it is also one of two Ponto-Caspian gobies that successfully settled in the Great Lakes of North America introduced there with ballast waters (Jude et al. 1992).The invasion of Ponto-Caspian gobies might be interpreted as a continuation of postglacial colonization and adaptation to local conditions created after Pleistocene, combined with passive dispersal due to water transport (Ahnelt et al. 1998) and other man-made changes in lotic ecosystems like e.g.damming, alteration of river banks (Copp et al. 2005).Moreover, the Ponto-Caspian gobies possess several biological attributes that seem to facilitate their invasion, i.e. phenotypic plasticity (Kováč and Siryová 2005;L'avrinčikova et al. 2005), effective reproductive tactics (Grabowska 2005), opportunistic feeding strategy (Grabowska and Grabowski 2005;Kakareko et al. 2005)

Figure 4 .
Figure 4. Expansion of Ponto-Caspian gobies in Poland.1: round goby (solid line -present distribution; dot -place of first record in Poland); 2: racer goby (solid line -present distribution; dashed line -route of invasion from the Dnieper River system; dot -place of first record in Poland); 3: monkey goby (solid line -present distribution; dashed lineroute of invasion from the Dnieper River system; dot -place of first record in Poland); 4: possible direction of further migration for all four gobies; 5: tubenose goby -place of first record in Poland; 6: watersheds of river basins; 7: Polish border; 8: canals (see also Annex 1).
Vaate et al. 2002) 2005)elative to native species(Ondračková et al. 2005).Given the demonstrated dispersal and establishment success of the tubenose goby and the other three Neogobius species present in Polish inland waters (bij deVaate et al. 2002), these species are expected to disperse more widely throughout Western Europe via the so-called 'central corridor'.First records of Ponto-Caspian gobiids in Poland.