Black-mouthed goby

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Black-mouthed goby
Black-mouthed goby (Neogobius melanostomus)

Black-mouthed goby ( Neogobius melanostomus )

Systematics
Perch relatives (Percomorphaceae)
Order : Gobies (Gobiiformes)
Family : Gobies (Gobiidae)
Subfamily : Benthophilinae
Genre : Neogobius
Type : Black-mouthed goby
Scientific name
Neogobius melanostomus
( Pallas , 1814)

The black-mouthed goby ( Neogobius melanostomus , syn .: Apollonia melanostomus ) is a small, European brackish and freshwater fish . Originally native to the south-eastern European brackish water areas of the Black and Azov Seas , the black-mouthed goby gained fame because of its explosive spread as a neozoon in waters in which it is not native, namely the North American Great Lakes and numerous waters in Central and Eastern Europe, including the brackish water areas from the North and Baltic Seas as well as the river systems of the Rhine , Elbe , Danube and other rivers . Mainly she got into these new habitats as a stowaway in the ballast tanks of large cargo ships. Due to its massive increase in newly populated waters, in which it often becomes the numerically dominant fish species within a short period of time, it is considered to be one of the most important fish neozoa in the world; its dispersal behavior is intensively researched.

Surname

The German common name Schwarzmund-Grundel is derived from the scientific species name melanostomus , which also means "black mouth" , as do numerous equivalents in other European languages ​​(e.g. Dutch Zwartbekgrondel , Swedish Svartmunnad smörbult ) .

In its Russian-speaking homeland, however, it is known as Bychok-krugljak ( Russian Бычок-кругляк ) or "round goby", to which its English name Round Goby corresponds, due to its body shape .

features

Dorsal fins with a conspicuous eye-spot on the anterior dorsal fin
Males at mating season with deep black coloring

The black-mouthed goby is elongated, largely round in cross-section and laterally flattened towards the caudal fin. The head is rounded in profile with a deep-set, but nevertheless terminal mouth and “bulging eyes” sitting on top of the head, protruding slightly from the skull profile. It has two dorsal fins, the front consisting of 5 to 8 hard rays, the elongated rear one consisting of a hard ray and 12–17 soft rays. The anal fin is of similar length and size as the opposite rear dorsal fin and consists of a hard ray and 9–15 soft rays. The symmetrical caudal fin is rounded. As is usual with gobies, the pelvic fins are fused into a single, suction cup-like disc.

In exceptional cases, black-mouthed gobies can live up to 6 years, but a lifespan of 3 to 4 years is more common. Males often die after their first breeding season, while females usually live for several years even in the adult state. The average total length (head tip to tail tip) of adult animals is around 15 cm, but old animals can reach body lengths of over 20 cm. The size depends on the habitat, so an average height of around 16 cm was measured in 3-year-old males in the brackish water of the southern Black Sea, which is roughly twice the size of their peers in the American Huron Sea (around 8 cm).

The black-mouthed goby is generally of inconspicuous coloration with the upper side, flanks and head often in camouflaging patterns of various brownish shades. The underside, on the other hand, is completely white. Along the side line there is a series of horizontal, elongated spots that give the impression of a regularly broken line. There is a noticeable eye spot on the anterior dorsal fin. It also has a characteristic line drawing below the eyes.

In the breeding season from April to September, the male black-mouthed gobies take on an extremely dark, almost deep black color.

Systematics

The closest relatives of the black-mouthed goby are the river gobies ( Neogobius fluviatilis ) and Neogobius caspius . These three species together form the genus Neogobius . Sister group of this genus are the Benthophilini with 5 kinds. These 8 species are in turn opposed to the 16 species of the Ponticolini , together they all form the subfamily Benthophilinae within the goby family (Gobiidae).

 Benthophilinae  

 Ponticolini 


  NN  
 Neogobius  


 Black-mouthed goby ( Neogobius melanostomus ) 


   

 River goby ( N. fluviatilis ) 



   

 N. caspius 



   

 Benthophilini 




Another work that deals with the phylogeny of the entire Gobiidae has confirmed these results in the core, although instead of the Benthophilini the Ponticolini were identified as a direct sister group. The relationship between the three closely related tribes Neogobiini, Benthophilini and Ponticolini is therefore initially unclear.

distribution

Distribution area (green) and distribution area (red)

The black mouth goby originally comes from the coastal brackish water zones of the region known as Pontokaspis with the inland seas Black Sea , Sea of ​​Azov and with the subspecies Neogobius melanostomus affinis on the western coast of the Caspian Sea . It also inhabits the lower courses of the rivers that flow into these seas.

Spread as an invasive species

In addition to the Kessler goby , the marbled goby , the river goby and the naked- necked goby, the black-mouthed goby is one of the pontocaspic gobies that have spread with astonishing speed beyond their original range in numerous water systems in Europe and sometimes even in North America . Once established, the goby populations sometimes multiply extremely rapidly and within a few years become the numerically dominant fish species of the infested waters, they are therefore perceived as a nuisance in many places. All five invasive goby species together are occasionally grouped together as Black Sea gobies in German-speaking countries . This designation of origin must not be misunderstood as a biological taxon, as the five species within the goby family (Gobiidae) come from four different genera.

A significant type of distribution of the black mouth goby is via the ballast water of cargo ships. While adults live mainly on the bottom of the water, young animals rise to the surface of the water at night to eat zooplankton . Here the cargo ships pick them up unintentionally. This is underpinned by parasitological studies, as the displaced black-mouthed goby populations are infested by parasites to a much lesser extent than the original populations in the Pontokaspis. The younger the animals are, the lower the parasite infestation. If adult animals had been dragged into the ballast water, it would have been very likely that they would have brought higher numbers of parasites with them.

North American Great Lakes

The black-mouthed goby was introduced into the North American Great Lakes in the ballast water of ships , where it has spread rapidly. It was first recorded in the Great Lakes ecosystem in 1990 in the St. Clair River on the US-Canadian border. In the following 10 years it spread across almost the entire water system. The most affected is Lake Erie , the southernmost of the Great Lakes. In the northern Upper Lake, on the other hand, the black-mouthed goby was only able to establish itself fragmentarily in some tributaries and port basins, which is due to its preference for warmer habitats.

Via the Illinois and Michigan Canal , it was able to penetrate far into the Illinois River and thus also into the water system of the south-flowing Mississippi .

The spread was intensified by anglers who caught the black-mouthed goby in an already infested body of water and then used it as bait fish in another. Live specimens that had escaped or were released after fishing were unintentionally spread as a result. In this way, the species has now been introduced to the Canadian lakes Lake Simcoe and Rice Lake and the Shiawassee River and Flint River , among others .

The wandering mussel also comes from the brackish water of the Pontokaspis and reached the Great Lakes in the same way as the black-mouthed goby (as a stowaway in cargo ships), where it spread invasively as early as the 1980s. The later spread of the black-mouthed goby was seen as evidence of the invasional meltdown effect, according to which the previous spread of a neozoon (the migrating mussel) leads to the subsequent spread of other neozoa (e.g. the black-mouthed goby), which need their “predecessor” as a source of food in order to gain a foothold in a new habitat, so that the range of species in the new habitat increasingly aligns itself with the habitat of origin, while the original species are gradually displaced. However, this thesis is now - at least with regard to the mongoose and black-mouthed goby - refuted, since the monger mussel only makes up a relatively small part of the diet of the black-mouthed goby and the latter can and can survive even in waters without migratory mussels (or physiologically similar mussel species) in truth prefers to feed on soft invertebrates such as amphipods and insect larvae. The black-mouthed goby established itself in the waters of Europe without the migrating mussel previously spreading.

European waters

In the ballast water of ships and also naturally, the black-mouthed goby has now been able to spread to the North and Baltic Seas and, as a neozoon, colonizes numerous European waters in which it is not originally native. A spread along the Danube has been documented since the 1990s , and in 2004 it was first found in the German part of the Danube. In the catchment area of ​​the Rhine, two originally isolated populations have been spreading since around 2008, one upstream from the Dutch Rhine delta and one downstream from the Danube via the Main-Danube Canal , which finally met. In the meantime, the black mouth goby has been detected in the entire catchment area of ​​the Rhine including its large tributaries such as the Main , Mosel , Lahn and Neckar . Other waters in which the black-mouthed goby is now widespread as a neo-zoon include the Volga , Trave , Oder and Eider .

The European expansion process is more complex than the North American one. On the one hand, the black-mouthed goby arrived here, as in America, as a stowaway in ballast tanks, and on the other hand, man-made waterways play an important role, which enabled the black-mouthed goby to independently conquer new habitats.

Biologists have identified 3 routes along which the black-mouthed goby was abducted in Europe. The northern route leads from the mouth of the Volga in the Caspian Sea upstream and finally over the Volga-Baltic Sea Canal to the eastern Baltic coast. The central route begins in the Black Sea in Ukraine at the mouth of the Dnepr , which is connected upriver in Belarus via the Dnepr-Bug Canal with the Bug and thus the Vistula river system. The southern route runs over the Danube and the Main-Danube Canal to the Rhine. The inland cargo ships sailing along these waterways have been identified as the main trigger for the European goby expansion.

As early as 1990, the black-mouthed goby was introduced into the Polish Gdańsk Bay using ballast water , where it spread until the late 1990s and finally established itself in the lower Vistula around the turn of the millennium . Presumably from the Danzig Bay, the natural spread westward along the Baltic Sea coast in Greifswalder Bodden , Pomeranian Bay , Stettiner Haff and Fischland-Darß-Zingst . From the Szczecin Lagoon, it settled the Peene in 2006 and the Oder in 2013 . The species is also spreading eastward along the Baltic Sea coast, and has since been detected in the Gulf of Riga in 2002 and in the Gulf of Finland in 2005 and also on the southern coast of Sweden.

In a separate process, the species also established itself as a stowaway in the ballast water, also far west on the North Sea , where it was first detected in 2004 in the Dutch Lek , an estuary of the Rhine . In 2008 it had spread upriver into the German Rhine near Dormagen .

From the lower Danube, where it is native to about the Bulgarian Vidin , it spread upstream in the course of the 1990s. In 1997 it was detected for the first time in the Serbian part and in 2000 in the Austrian part of the Danube. In 2004 it had penetrated into the German part as far as Straubing . Via the Main-Danube Canal , it finally reached the Main , then the Rhine. Around 2008, the goby population from the Danube and the upstream goby population that was brought in via the ballast water into the Netherlands met in the Rhine; in the meantime it has established itself in the entire water system including its major tributaries, for example in the Moselle and Neckar , and since 2011 far upstream in the Swiss Rhine.

The black-mouthed goby was first detected in Belgium in 2010, where it colonized the Scheldt , among other places .

Phylogenetic studies indicate that both the black-mouthed gobies, which are widespread in the Dutch-Belgian North Sea and in the Great Lakes, originally come from the delta of the Dnieper on the Black Sea. Therefore, the Ukrainian port of Cherson located here is assumed to be the place of origin. It is possible that the animals came directly from the Black Sea to the European ports, but it is also possible that they were brought back to Europe indirectly from the Great Lakes of North America. However, studies by other scientists have shown that the black-mouthed gobies in the Great Lakes come from different places of origin and show great phylogenetic diversity.

The black-mouthed goby was also detected in the Aegean Sea of Turkey as early as 2001 .

Way of life

The banks of the Rhine fortified with coarse rock fillings: ideal habitat for the black-mouthed goby

The black-mouthed goby is not a good swimmer. It has no swim bladder and therefore lives largely close to the ground and usually does not venture into open water.

Young animals tend to live on sandy, adult animals on hard, stony bottom. It could be that young animals specifically seek out this habitat, or that the smaller and weaker young animals are displaced there by the stronger adult black-mouthed gobies and have to be content with a suboptimal habitat until they are large enough to assert themselves. The black mouth goby prefers rather shallower water areas close to the shore up to a depth of about 3 meters. It only colonizes deeper or more sandy areas if there is sufficiently strong intra-species competitive pressure. In North American Lake Erie, which of all five of the Great Lakes is most severely affected by the goby invasion, black-mouthed gobies have been detected to a depth of 130 m. The fondness of the black-mouthed goby for stony habitats is often encouraged by man-made structures, since in Central Europe many of the large rivers used as traffic arteries as well as canals on the banks are in large parts paved with coarse stones.

The black-mouthed goby is quite cold-tolerant, but prefers warmer habitats. The energy optimum is at a water temperature of around 26 ° C. In colder waters, the populations are significantly smaller than in warmer ones, the invasive infestation is much slower and more fragmented. An example of this is the contrast in North America between the (colder) Lake Superior with a low goby population and the (warmer) Lake Erie with extremely heavy infestation.

A relatively high tolerance to salt water enables the black-mouthed goby to live in both fresh and salt water. In the Baltic Sea, with its low salinity of 0.8%, the black-mouthed goby was able to establish itself along the coasts far away from the estuaries, while in the salty North Sea (salinity of around 3.5%) it was limited to the brackish water areas near the river. It is not clear why some populations of the black-mouthed goby in their region of origin on the Caspian Sea can also flourish in habitats with a salinity of over 4%. The black- mouthed goby is probably more tolerant of calcium sulfate (CaSO 4 ) found in the Caspian Sea than of sodium chloride (NaCl), which is common in the world's oceans .

nutrition

As a young animal, the black-mouthed goby eats zooplankton on the surface of the water. Adult animals feed primarily on small invertebrates such as amphipods or insect larvae that live in water, such as mosquitoes and mayflies . Water snails and smaller mussels, especially the migrating mussel , also make up a certain part of their food spectrum. The black-mouthed goby can break open the hard shells of these animals with their powerful goby teeth.

Threat to other fish species

The feeding behavior of the black-mouthed goby has been the subject of numerous studies, which were largely driven by the concern that it could threaten the population of native fish species in newly populated waters as a spawning predator and predator of young fish. This fear was obvious, since the goby prefers to stay in areas close to the shore, such as rock beds. Such structures are considered to be the “nurseries” of numerous fish species that spawn here as well as spend their larval and juvenile stages, largely protected from open water predators such as perch , asp and pike . The presence of black-mouthed gobies led to the fear that juvenile fish would now also be stalked in this supposedly protected area and that they would no longer have any opportunity to reach a reproductive age.

The Federal Agency for Nature Conservation rated the black-mouthed goby as an invasive neozoa in 2010, and the species was added to the black list of invasive species together with the other immigrated goby species . It was feared that the impact on local biodiversity would result from competition with local bottom fish such as Mühlkoppe and nerd and strong predation pressure on aquatic mollusks . The possible hybridization with the river goby, however, is considered to be less problematic because this species is also a neozoon.

In a study from 2011 , the stomach contents of over 100 black-mouthed gobies were examined in the Czech Danube tributary Thaya , where the black-mouthed goby has been recorded as a neozoon since 2008. Contrary to initial expectations, however, practically no fish eggs or juvenile fish were found in the animals' stomachs (less than 1% of the food found in the stomachs). The animals examined were taken in May and June, the period in which most fish species reproduce and thus the amount of both fish spawn and young fish in the water is greatest. Despite this offer, the black-mouthed goby continued to feed almost exclusively on small invertebrates at this time. Contrary to initial fears, the threat of the black-mouthed goby to other fish species from direct predation is therefore classified as low.

Niche competition with other invasive goby species

The black-mouthed goby shares its way of life near the ground (benthic), the preference for stone structures near the shore and also its eating and reproductive habits, above all with the other neozoa. From the perspective of the black-mouthed goby, the main competition is not native fish, but the other invasive goby species. In terms of numbers, the black-mouthed goby is the most common goby neozoon in all Central European waters. She seems to be even better at conquering new habitats than her relatives.

Reproduction

Clutch

Females are sexually mature after 3 years at the latest, males after 4 years at the latest. In each season, which lasts on average from April to September, the females spawn several times, as they have formed new spawn every 3 to 4 weeks. The male, colored jet black at that time, builds a nesting site by using his caudal fin to scoop up the soft ground beneath a stone (or other hard object), creating a kind of cave. This process takes up to 10 days. With the help of pheromones and acoustic vocalizations, females are then attracted, which attach their spawn upside down to the underside of the stone. Up to six females spawn in a nesting cavity, a total of up to 10,000 eggs per clutch. The male then guards the clutch until the larvae, which are about 5 mm in size, hatch, and it also cares for the eggs by regularly fanning fresh water into the cave. It does not eat during this time, but attacks intruders of all sizes with great aggressiveness, even fish species that can be dangerous to itself.

Interesting behavior was observed in areas with high population and competitive pressures. Individual males do not build their own nest holes and do not adopt a black spawning dress. Instead, they follow the lure tracks to other males' nesting sites and behave like females there to gain access to the nesting cavity. There they try to fertilize the spawn that has already been laid by real females with their own milk and then move away. The actual builder of the nesting site then guards the (partially or completely) not fertilized eggs.

Predators

The burbot, one of the beneficiaries of goby immigration

In the American Great Lakes, burbot , black bass , American river perch , American char and glass-eyed perch are among the predators of the black-mouthed goby. Some predatory fish, especially the burbot living in the ground, have even benefited from the arrival of the goby. According to mathematical models, almost two-thirds of all adult black-mouthed gobies end up as prey for burbot in Lake Erie. Since the immigration of the black-mouthed goby, the burbot has grown much faster than in previous years due to the abundant food supply. It is similar with the black bass, which also prefers to hunt in shallow and stony water zones and thus prey on numerous gobies. In contrast, open water predators such as the Arctic char only occasionally prey on the black-mouthed goby and do not hunt them specifically. With the signet ring swimming snake and ear shag , water snakes and birds are also predators of the black-mouthed goby in North America.

In Central European rivers, the predatory fish species perch , pikeperch , catfish and broad-headed eel seem to be increasingly adjusting to the goby species as the new main prey. German anglers report that over the years, for example in the Rhine and its tributaries, catfish and pikeperch can be better caught with black-mouthed gobies as bait fish, and that many dead gobies can often be found in the digestive tract of captured predatory fish. It is still unclear whether the European burbot populations benefit from the black-mouthed gobies to the same extent as their American relatives.

In the brackish water of the Baltic Sea it is not only the perch but also the cod that the black-mouthed goby prey on. Birds that hunt fish with the gray heron and cormorant are also important, the latter being the primary predator of the black- mouthed goby in the Bay of Danzig .

Black-mouthed goby and human

In their homeland, the black mouth goby is used for culinary purposes.

In new habitats, including the major German rivers, the relationship between anglers and black-mouthed gobies is often problematic. The species is often perceived as a nuisance, as its occurrence makes fishing for native fish species such as roach or bream very difficult, as the black-mouthed goby is often first at the bait due to its sheer mass. On the one hand it is for the German national fishing rights prohibited massive reset not geschonte fish, so must each caught goby waidgerecht killed and meaningful use are supplied. In addition, it is increasingly found that many anglers do not want to release caught black-mouthed gobies at all , because they believe they are exercising a certain level of stock control through their activities. On the other hand, the black-mouthed goby is unknown in culinary terms in this country and is also difficult to use due to its small body size. Individual gobies can be used as bait for predatory fish such as pikeperch and catfish, but the number of animals caught often exceeds the angler’s needs. In order to give the catch of these animals a fishing sense, anglers' associations are trying to promote the gobies as food to anglers more, for example by spreading recipes from Eastern Europe.

literature

  • Jörg Andreas Brandner: Ecology of the invasive neogobiids Neogobius melanostomus and Ponticola kessleri in the upper Danube River . Munich 2014
  • MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 235-285.
  • Merlijn Mombaerts, Hugo Verreycken, Filip AM Volckaert, Tine Huyse: The invasive round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris: Two introduction routes into Belgium . In: Aquatic Invasion , No. 90-3, 2014, pp. 305-314.

Web links

Commons : Black Mouth Goby  - Album with pictures, videos and audio files

Individual evidence

  1. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 236-237.
  2. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, p. 247.
  3. ↑ a b M.S. Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, p. 237.
  4. ^ Matthew E. Neilson, Carol A. Stepien: Escape from the Ponto-Caspian: Evolution and biogeography of an endemic goby species flock (Benthophilinae: Gobiidae: Teleostei) . In: Molecular Phylogenetics and Evolution , No. 52, 2009, pp. 91-94.
  5. ↑ Christine E. Thacker & Dawn M. Roje: Phylogeny of Gobiidae and identification of gobiid lineages . In: Systematics and Biodiversity 9 (4), 2011, pp. 329–347. doi : 10.1080 / 14772000.2011.629011
  6. ↑ cf. about the information page "Black Sea Gobies". Landesfischereiverband Baden-Württemberg eV, March 10, 2014, archived from the original on March 10, 2014 ; Retrieved June 17, 2016 .
  7. ↑ a b c d Johannes Ungemach: Invasion of the Black Sea gobies. In: Main-Post . November 7, 2013, accessed June 17, 2016 .
  8. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 237-238.
  9. ↑ Merlijn Mombaerts, Hugo Verreycken, Filip AM Volckaert, Tine Huyse: The invasive round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris: Two introduction routes into Belgium . In: Aquatic Invasion , No. 90–3, 2014, p. 311.
  10. ^ Matthew E. Neilson, Carol A. Stepien: Escape from the Ponto-Caspian: Evolution and biogeography of an endemic goby species flock (Benthophilinae: Gobiidae: Teleostei) . In: Molecular Phylogenetics and Evolution . tape 52 , no. 1 , 2009, p. 84-102 , doi : 10.1016 / j.ympev.2008.12.023 .
  11. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 238-40; 248.
  12. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, p. 240.
  13. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 240-241.
  14. ↑ a b c Mojmír Vašek / Lucie Všetičková / Kevin Roche / Pavel Jurajda: Diet of two invading gobiid species (Proterorhinus seminularis and Neogobius melanostomus) during the breeding and hatching season: No field evidence of extensive predation of fish eggs and fry . In: Limnologicus , No. 46, 2013, pp. 31-36.
  15. ↑ a b Bernd Stemmer: River goby in the Rhine water system: Fourth new goby species detected in the North Rhine-Westphalian Rhine . In: Natur in NRW , No. 4, 2008, pp. 57–60.
  16. ↑ Fish from the Black Sea conquered Lübeck's waters. In: Lübecker Nachrichten . August 13, 2011, accessed August 24, 2013 .
  17. ^ Jörg Andreas Brandner: Ecology of the invasive neogobiids Neogobius melanostomus and Ponticola kessleri in the upper Danube River . Munich 2014, p. 14.
  18. ^ Christian Schomaker, Christian Wolter: First record of the round goby Neogobius melanostomus (Pallas, 1814) in the lower River Oder, Germany . In: BioInvasions Records , No. 3–3, pp. 185–188
  19. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, p. 241.
  20. ↑ a b c d Jörg Andreas Brandner: Ecology of the invasive neogobiids Neogobius melanostomus and Ponticola kessleri in the upper Danube River . Munich 2014, p. 14.
  21. ↑ Merlijn Mombaerts, Hugo Verreycken, Filip AM Volckaert, Tine Huyse: The invasive round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris: Two introduction routes into Belgium . In: Aquatic Invasion , No. 90–3, 2014, p. 311.
  22. ↑ J. Borcherding et al. (2011): Non-native Gobiid species in the lower River Rhine (Germany): recent range extensions and densities. In: Journal of Applied Ichthyology, 27.1, pp. 153-155.
  23. ↑ Merlijn Mombaerts, Hugo Verreycken, Filip AM Volckaert, Tine Huyse: The invasive round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris: Two introduction routes into Belgium . In: Aquatic Invasion , No. 90-3, 2014, pp. 306-307.
  24. ↑ Merlijn Mombaerts, Hugo Verreycken, Filip AM Volckaert, Tine Huyse: The invasive round goby Neogobius melanostomus and tubenose goby Proterorhinus semilunaris: Two introduction routes into Belgium . In: Aquatic Invasion , No. 90-3, 2014, pp. 311-312.
  25. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, p. 240.
  26. ↑ a b c d M.S. Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 248-249.
  27. ^ MS Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 237-238.
  28. ↑ Stefan Nehring, Franz Essl, Frank Klingenstein, Christelle Nowack, Wolfgang Rabitsch, Oliver Stöhr, Christian Wiesner, Christian Wolter: Black List of Invasive Species: System of Criteria and Black Lists of Invasive Fish for Germany and Austria . Ed .: Federal Agency for Nature Conservation BfN (=  BfN scripts 285 ). 2010, p. 102 ( bfn.de [PDF]).
  29. ↑ a b M.S. Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 243-245.
  30. ↑ a b M.S. Kornis, N. Mercado-Silva, MJ Vander Zanden: Twenty years of invasion: A review of round goby Neogobius Melanostomus biology, spread and ecological implications . In: Journal of Fish Biology , No. 80, 2012, pp. 262-263.
  31. ↑ Lynda D. Corkum, Mariusz R. Sapota, Krzysztof E. Skora: The round goby, Neogobius melanostomus, a fish invader on both sides of the Atlantic Ocean . In: Biological Invasions , No. 6, 2004, p. 173.