The stone moroko (''Pseudorasbora parva''), also known as the topmouth gudgeon, is a fish belonging to the

Cyprinid Cyprinidae is a family of freshwater fish commonly called the carp or minnow family. It includes the carps, the true minnows, and relatives like the barbs and barbels. Cyprinidae is the largest and most diverse fish family and the largest verte ...

family, native to

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, but introduced and now considered an

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

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and

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. The fish's size is rarely above 8 cm and usually 2 to 7.5 cm long.

Invasive species

In Europe, ''P. parva'' is included since 2016 in the list of Invasive Alien Species of Union concern (the Union list). This implies that this species cannot be imported, bred, transported, commercialized, or intentionally released into the environment in the whole of the European Union. The fish was introduced in the 1960s into ponds in

Nucet Nucet (; hu, Diófás) is a town in Bihor County, western Transylvania, Romania. Its name means "walnut trees" both in Romanian and Hungarian. It administers two villages, Băița (''Rézbánya'') and Băița-Plai. The uranium-producing Băi� ...

Dâmbovița County Dâmbovița County (also spelt ''Dîmbovița'', ) is a county ( județ) of Romania, in Muntenia, with the capital city at Târgoviște, the most important economic, political, administrative and cultural center of the county. It has an area o ...

Romania Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...

and it made its way into

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, then spreading throughout Europe. They pose danger to other species such as the sunbleaks (''

Leucaspius delineatus ''Leucaspius delineatus'', known as the sunbleak, belica or moderlieschen is a species of freshwater fish in the family Cyprinidae. It is currently the only species included in genus ''Leucaspius'', whereas formerly others were included, which n ...

''). They are the carrier of a parasite (''

Sphaerothecum destruens ''Sphaerothecum destruens'' (the rosette agent) is a parasite of fish. It was first discovered in the United States in association with invasive species including topmouth gudgeon, but was found to be the causative agent of a disease in the UK ...

'') that is not damaging to the topmouth gudgeon, but attacks other fishes like the sunbleaks, which are unable to spawn and have a higher mortality when infected."The Gudgeon and the Sunbleak"

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June 28, 2005 They also feed on eggs of locally valuable native fish species. The species has also been recently discovered in several lakes in the UK where it is believed to have been illegally stocked. This has called for a large scale eradication programme organised by the Environment Agency who kill the fish off with a piscicide called

rotenone Rotenone is an odorless, colorless, crystalline isoflavone used as a broad-spectrum insecticide, piscicide, and pesticide. It occurs naturally in the seeds and stems of several plants, such as the jicama vine plant, and the roots of several mem ...

References

{{Taxonbar, from=Q583540 Pseudorasbora Taxa named by Coenraad Jacob Temminck Taxa named by Hermann Schlegel Fish described in 1846