Pseudorasbora parva | Topmouth Gudgeon



Conservation status

Least concern

Legal status

Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].


Invasive species - risk of High Impact

Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Pet/aquarium species, Live food and live bait

Introduction pathways - 2

Transport Contaminant

Introduction pathways subclass - 2

Transport of habitat material

Invasive score


NAPRA Ireland risk assessed


Species Biology


Small elongated fish usually 8-9cm long. Males and females similar colour out of spawning season - grey back and lighter side and belly (yellowish green to silver). Juveniles have a dark stripe along each side. Short dorsal and anal fins. Large, deeply incised caudal fin (Hubble, 2012). All fins are rounded (Environment Agency, undated). Large scales (Hubble, 2012). Upturned lower jaw (Environment Agency, undated). Lives for 3-4 years (Hubble, 2012).


Decreases biodiversity by competing with native (and farmed) species for food, space and spawning area (Panov, 2006). Predates invertebrates, juvenile fish (Panov, 2006) and fish eggs (European Commission, 2017). Further impacts native species by carrying infectious diseases such as Pike Fry Rhabdovirus and parasites including Anguillicolla crassus and the rosette agent, Sphaerothecum destruens. Known nuisance species for anglers as it is a non-target species but readily takes bait (Panov, 2006). May also impede the reproduction of native fishes (Britton & Brazier, 2006 as cited in NNSS, 2011).


Males and females become sexually dimorphic during spawning. The males darken and develop tubercles on the head and lower lip, while the females become paler (Hubble, 2012). Females first spawn at 1 year old in April-June (Panov, 2006). Spawning is multi-litter, up to 4 times per year and requires a minimum temperature of 15-19°C (Hubble, 2012). First, she cleans the area where the eggs are to be laid. Hundreds to thousands of eggs are produced, which are laid on plants, sand, stones, shells etc. The male provides parental care, aggressively guarding the eggs until hatching (Panov, 2006).

Pathway and vector description

Has been introduced to much of its non-native range as a contaminant of fish stocks. Its small size makes it capable of hiding under the gills of larger species (NNSS, 2011). Other potential pathways are as live bait inadvertently carried between waterways or the inappropriate dumping of aquariums (NNSS, 2011). Once established they can readily disperse as eggs laid on boats, floating aquatic plants or as contaminants on angling gear (Hubble, 2012).

Mechanism of impact

Competition, Predation, Disease transmission

Management approach

There is currently an EU wide ban on the keeping or releasing of this species (European Commission, 2017).


Piscicides can be used (e.g. Rotenone) as was used in Ratherheath Tarn in Cumbria (Hubble, 2012) but they are non-selective, expensive, have health and safety considerations and are suitable only for use in small water bodies. It may also be problematic in the context of species of conservation concern. Water draw-down and liming can be an effective alternative to rotenone (Britton & Brazier, 2006 as cited in NNSS, 2011) but again this method is suitable only for small water bodies.


Britton et al. (2010) achieved a high rate of control (99.5%) in 2 years by using micro-mesh seine nets in April prior to spawning and again in September to catch any young produced that year. Its effectiveness however, was aided by the small size and shallowness of the lake.

Broad environment


Habitat description

Small lakes, ponds, ditches, slow-flowing rivers, irrigation canals (Panov, 2006). Likes still or slow-flowing water with dense aquatic vegetation (Hubble, 2012).

Species group


Native region

Temperate Asia


World distribution(GBIF)

Introduced in the EU in Austria, Belgium, Croatia, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Italy, Luxembourg, the Netherlands, Poland, Romania, Slovakia, Slovenia, Spain, the United Kingdom (European Commission, 2017).

Native distribution

Eastern Asia including Korea and Japan (NNSS, 2011).

Temporal change

Records submitted to Data Centre in 2024

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre.

Do not purchase or dispose of in the wild.



Britton, J.R. & Brazier, M. (2006) Eradicating the invasive topmouth gudgeon, Pseudorasbora parva, from a recreational fishery in northern England. Fisheries Management and Ecology 13, 329–335.

Britton, J.R.; Gareth, D.D.; Brazier, M. (2010) Towards the successful control of the invasive Pseudorasbora parva in the UK. Biological Invasions, 12 pp. 125-131. DOI 10.1007/s10530-009-9436-1  Site accessed 18 October 2017.

Environment Agency – UK (undated) Topmouth gudgeon – Pseudorasbora parva. Fact sheet. Site accessed 18 October 2017.

European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.

Hubble, D. (2012) Topmouth gudgeon, Pseudorasbora parva. Factsheet. Non-native Species Secretariat (NNSS). Site accessed 18 October 2017.

Non-native Species Secretariat (NNSS) (2011). Invasive Species Action Plan for Topmouth gudgeon (Pseudorasbora parva). Site accessed 18 October 2017.

Non-native Species Secretariat (NNSS) (2011). GB Non-native Organism Risk Assessment for Pseudorasbora parva – Topmouth gudgeon. Site accessed 18 October 2017.

Panov, V (2006). Delivering Alien Invasive Species Inventories for Europe Factsheet – Pseudorasbora parva. Site accessed 18 October 2017.

Witkowski, A. (2011): NOBANIS – Invasive Alien Species Fact Sheet – Pseudorasbora parva. – From: Online Database of the European Network on Invasive Alien Species – NOBANIS Site accessed 18 October 2017.

Fishbase Species Information

Invasive Alien Species in Northern Ireland Factsheet

Additional comments

Also commonly known as the Stone moroko.