Leuciscus parvus Schlegel, 1842; Leuciscus pusillus Temmnick et Schlegel, 1846; Fundulus virescens Temmnick et Schlegel, 1846; Leuciscus pusillus Temmnick et Schlegel, 1846; Micraspius mianowski Dybowski, 1869; Aphiocypris chinensis Fowler, 1924; Pseudorasbora altipinna Nichols, 1925; Pseudorasbora fowleri Nichols, 1925; Pseudorasbora depressirostris Nichols, 1925; Pseudorasbora monstruosa Nichols, 1925; Pseudorasbora parva parvula Nichols 

Pseudorasbora parva has the necessary life history traits—including early maturity, batch spawning, nest guarding, and broad environmental tolerance limits—to establish sustainable populations after being introduced into new environments (Ricciardi and Rasmussen 1998; Ye et al. 2006; Zahorska and Kovac 2009). Pseudorasbora parva life history traits are also highly plastic which facilitates the species’ adaptation to new environments and changing conditions (Rosecchi et al. 2001; Beyer et al. 2007; Britton et al. 2008b; Zahorska and Kovac 2009; Zahorska and Kovac 2013). At low densities in invaded ecosystems, P. parva tends to exhibit faster growth, earlier maturation, and higher fecundity (Britton et al. 2008b; Zahorska and Kovac 2009) compared to high density populations or in its native range. Pseudorasbora parva also is typically larger in lower latitudes where temperatures are warmer (Gozlan et al. 2010), but at local scales population density and the phase of establishment are more determinant of body size than is temperature (Katano and Maekawa 1997; Britton et al. 2008b; Davies and Britton 2015).

Pseudorasbora parva’s plasticity is demonstrated by its highly flexible reproductive strategy. Sexual maturity is usually reached in the first year of life (Zahorska and Kovac 2009), but delayed maturation has been observed in high-density populations (Britton et al. 2008b). Once mature, P. parva will spawn in batches asynchronously during the spring and summer months, typically from April to August in its native range (Katano and Maekawa 1997; Britton et al. 2008b; Gozlan et al. 2010). In its non-native range, P. parva may begin spawning in early March and continue into September (Gozlan et al. 2010). Asynchronous spawning improves larvae survival rates by reducing their susceptibility to changing environmental conditions (Katano and Maekawa 1997). A single female can lay 121 to 7124 eggs throughout the spawning season (Katano and Maekawa 1997; Pinder and Gozlan 2003; Britton et al. 2008b; Zahorska and Kovac 2009; Zahorska and Kovac 2013). Zahorska and Kovac (2013) found that P. parva significantly increased its average absolute fecundity following an environmental disturbance, further showing how a plastic reproductive strategy allows P. parva to adapt to changing conditions.  The incubation period of the eggs is approximately seven days at 20ºC (Pinder and Gozlan 2003).

Behavior of P. parva before, during and after spawning is thought to enhance reproductive success. Male P. parva establish and guard their nests to enhance the survival rate of their brood (Pinder and Gozlan 2003). Spawning substrate can vary but P. parva show preference for structures with a cavity, which are more defensible than flat surfaces (Pinder and Gozlan 2003). The sexual dimorphism exhibited by P. parva is associated with the male reproductive behaviors of nest building and guarding, and female batch spawning (Maekawa et al. 1996 in Gozlan et al. 2010). Courting behaviors typical in most cyprinids are observed in P. parva such as males chasing and leading females. The female then attaches the highly adhesive eggs to the substrate prior to male fertilization (Maekawa et al. 1996 in Gozlan et al. 2010).

Pseudorasbora parva is an omnivore whose diet generally includes zooplankton, micro-crustaceans, molluscs, fish eggs and larvae, algae, and plant detritus (Xie et al. 2000; Ye et al. 2006; Yalçin-Özdilek et al. 2013). Pseudorasbora parva will also feed opportunistically on floating objects such as plant seeds and terrestrial insects (Pinder and Gozlan 2003; Rolla et al. 2020). Small age-0 individuals feed predominantly on zooplankton and phytoplankton and will shift their diet to chironomids and other benthic organisms as they get older and larger (Declerck et al. 2002; Gozlan et al. 2010).

Potential pathway(s) of introduction: Hitchhiking/Fouling, Unauthorized Intentional Release

Pseudorasbora parva was introduced in Europe with stockings of herbivorous fishes (Cyprinus carpio, Ctenopharyngodon idella, Aristichthys nobilis, Hypophthalmichthys molitrix) imported from China (Panov 2006; Gozlan et al. 2010). The introduction and spread of P. parva in the United Kingdom has been linked to imports and movements of the ornamental variety of Ide (Golden Orfe), Leuciscus idus (Copp et al. 2010). Golden Orfe is sold in the Great Lakes area (e.g., William Tricker, Inc: http://www.tricker.com/Category/golden-orfe-fish). Pseudorasbora parva spread throughout Lithuania via Ctenopharyngodon idella stockings and by natural dispersal in small rivers (Rakauskas et al. 2021). However, dispersal is likely limited by salinity as this P. parva is unable to hypo-osmoregulate (Smith et al. 2007a). Pseudorasbora parva is not known to be sold in North America, but as mentioned previously, it may contaminate other fish stocks. Ornamental fish species are sometimes intentionally released by aquarium owners into sewer and drains which allows for these species to be introduced into streams and rivers that drain into the Great Lakes.

Pseudorasbora parva has a Moderate probability of establishment if introduced to the Great Lakes (Confidence level: High).

The life history traits of this species that would suggest its establishment success include a wide tolerance of environmental conditions, reaching sexual maturity in the first year of life, batch spawning, and nest guarding (Pinder et al. 2005). In invaded regions of central Europe, P. parva exhibited alterations in reproductive behaviors (longer reproductive season and better nest guarding) that increased reproductive potential relative to native populations (Britton et al. 2008b; Zahorska and Kovac 2009; Kirczuk et al. 2021).The combination of these life history traits, and the range of invaded countries with contrasting climates (i.e. Algeria, Iran, Poland, Tibet) reveal the considerable plasticity and adaptability of P. parva to lentic and lotic conditions, Mediterranean, continental and Northern climates, and new food resources and spawning substrata (Gozlan et al. 2010). Furthermore, in an assessment of 16 fish species, P. parva had the highest niche breadth in some Chinese rivers indicating a high degree of environmental adaptability (Yang et al. 2019a). Its rate of spread is quite rapid, reaching across nearly the entire European continent within 60 years after being introduced into Romania in the 1960s (Gozlan et al. 2010).

The establishment of P. parva in the Great Lakes could be influenced by the impacts of climate change. In increased water temperatures simulating climate change, Muhawenimana et al. (2021) reported increased swimming performance of P. parva which can promote natural dispersal (Muhawenimana et al. 2021). On the other hand, P. parva is unable to survive in brackish waters and would likely suffer from increased salinization in the Great Lakes as a side effect of climate change (Scott et al. 2007b).

The establishment of P. parva could be hindered to some degree through predation by piscivores already in the Great Lakes. However, Esox lucius, Sander lucioperca, Salmo trutta, and Perca fluviatilis, have not prevented P. parva from establishing throughout Europe (Panov 2006; Britton et al. 2010; Rechulicz 2019).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental	Socioeconomic

Pseudorasbora parva is considered one of the most invasive fish species in Europe (Davison et al. 2017). It is host to a plethora of harmful parasites, is a strong competitor for resources, and can alter food web dynamics.

Pseudorasbora parva has at least 84 documented parasite species. Although, generally only a few of these are transferred to a new site of introduction. Specifically, these are typically zoosporic fungi (Czeczuga et al. 2002), parasites such as Gyrodactylus spp. (Ye et al. 2017), and viruses such as fry rhabdovirus (PFR) in Germany (Ahne and Thomsen 1986) and cyprinid herpesvirus (Pospichal et al. 2018). The PFR virus, which causes acute disease of Esox lucius fry, has been isolated from P. parva. The two most severe parasites found associated with P. parva in its invasive range are Anguillicola crassus and rosette agent Sphaerothecum destruens (Gozlan et al. 2005, 2010; Witkowski 2011; Combe and Gozlan 2018). These parasites, if carried over after introduction, could have destructive impacts on similar native or economically valuable Great Lakes species. For example, Sphaerothecum destruens infects Chinook salmon, Atlantic salmon, rainbow trout, and brown trout (Boitard et al. 2017). The dominance of P. parva in river floodplains of the IJssel, Meuse, Nederrijn and Waal River (Europe) and the co-spread of S. destruens is implicated in decline of native Leucaspius delineatus and Pungitius pungitius as well as the diversity of fish assemblages (Spikmans et al. 2020).

Due to its high reproductivity, adaptability, and competitive abilities, Pseudorasbora parva is one of the most (or the most) dominant species in fish assemblages where it is established (Tang et al. 2003; Kapusta et al. 2008; Peter et al. 2017). If introduced into the Great lakes, P. parva could cause noticeable stress or decline in at least one native population. Predator-prey relationships in the Great Lakes may be significantly adversely affected by the introduction of P. parva. Pseudorasbora parva exploits resources that are underexploited by native fishes contributing to its invasion success (Top-Karakus et al. 2021). In a pond study, P. parva overexploited zooplankton populations and outcompeted Cyprinus carpio for food (Kajgrová et al. 2022). In a separate study, P. parva was found to nibble on Cyprinus carpio and Tinca tinca causing injuries and deep lesions (Oberle et al. 2019). Pseudorasbora parva has a high overlap niche with Alburnus alburnus and is a potential over-competitor if resources are limited. Despite this, the two species can coexist in open ecosystems and thus potentially double their trophic impact (Balzani et al. 2020). As a generalized and opportunistic predator, P. parva competes with native fishes (Schizothorax o’connori, Schizopygopsis younghusbandi younghusbandi, and Ptychobarbus dipogon) for Bacillariophyta and Chironomid larvae in the invaded region of Chabaland Wetland, China (Ding et al. 2019). In an invaded river in Poland, P. parva had limited effects on fish community composition, yet the abundance of Perca fluviatilis and Leucaspius delineatus were negatively associated with occurrence of P. parva. Notably, Salmo trutta reduced P. parva abundance and possibly limited their impact in the river (Rechulicz 2019).

Pseudorasbora parva has a high potential socio-economic impact in the Great Lakes.

It is unknown whether P. parva poses hazards or threats to human health. Pseudorasbora parva does carry parasites that are able to infect humans (Zhou et al. 2008; Pak et al. 2009; Xu et al. 2010; Bao 2012). Specifically, it carries Clonorchis sinensis and Metorchis orientalis metacercariae which commonly infect humans (Yang et al. 2019b; Xie et al. 2022), but documentation of P. parva directly transferring these parasites to humans is limited (Gozlan et al. 2010). A series of three (successful) eradication exercises from United Kingdom lakes has cost approximately £130,000 in public funds (Britton et al. 2008a).

Pseudorasbora parva poses a threat to commercial and recreational fisheries. Pseudorasbora parva may outcompete native prey species and carry pathogens/parasites that are known to affect salmonids and Northern pike (Gozlan et al. 2010). Three fish species in Europe have declined by 80-90% following the invasion of P. parva. This trend coincided with increased prevalence of Sphareothecum destruens, a pathogen known to be carried by P. parva, in fish populations and specifically in the three declining species. Pseudorasbora parva is considered a major threat to the sea bass aquaculture industry in Europe (Ercan et al. 2015). In the United States, S. destruens has caused mass mortality in farmed and wild Chinook salmon in California where it caused >80% mortality of smolts (Harrell et al. 1986).

There is little or no evidence to support that Pseudorasbora parva has the potential for significant beneficial impacts if introduced to the Great Lakes.

It has not been indicated that Pseudorasbora parva can be used for the control of other organisms or improving water quality. There is no evidence to suggest that this species is commercially, recreationally, or medically valuable. It does not pose significant positive ecological impacts. Pseudorasbora parva has no economic value and it is only used by sport fishermen as bait fish (Lendhardt et al. 2011).

In the United States and its territories, the importation or transportation of this species is prohibited unless otherwise stated (18 U.S.C. 42 (Lacey Act)). In Canada, the use or possession of fish as live bait in any province other than from which it was taken is prohibited (SOR/93-55). This species is listed as injurious in Illinois and shall not be possessed, propagated, bought, sold, bartered or offered to be bought, sold, bartered, transported, traded, transferred or loaned to any other person or institution unless a permit is first obtained (17 Ill. Adm. Code Ch. I, Sec. 805). It is prohibited in Indiana, making it illegal to import, possess, propagate, buy, sell, barter, trade, transfer, loan, or release this species into public or private waters (312 IAC 9-6-7). It is prohibited in Michigan and is unlawful to possess, introduce, import, sell or offer this species for sale as a live organism, except under certain circumstances. (Natural Resources Environmental Protection Act (Part 413 of Act 451)). This species is prohibited in Minnesota and is unlawful (a misdemeanor) to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education (Statute 84D.07). In Ohio, it shall be unlawful for any person to possess, import or sell live individuals of this species (Ohio Administrative Code 1501:31-19-01). It is prohibited in Ontario, making it illegal to import, possess, deposit, release, transport, breed/grow, buy, sell, lease or trade this species (Invasive Species Act, 2015, S.O. 2015, c. 22 - Bill 41). In Quebec, this species cannot be used as bait. (SOR/90-214).

Note: Check federal, state, and local regulations for the most up-to-date information.

Control

Biological

Several studies have indicated that the presence of native predatory fish in an invaded ecosystem may effectively suppress P. parva populations (Csorbai et al. 2014; Lemmens et al. 2015; Boitard et al. 2017). However, the effectiveness of this control has varied in different cases. Lemmens et al. (2015) found that stocking of native northern pike (Esox Lucius) had a strong negative effect on the abundance and biomass of P. parva in ponds in Belgium. However, investigations of predation control in Ukrainian reservoirs found that the number of predators capable of feeding on P. parva is small and that P. parva comprised a small component of Northern pike’s diet in these reservoirs (Didenko and Gurbik 2011 in Tereshchenko 2016). In general, the effectiveness of stocking piscivorous fish to control invasive species has been highly variable and is not as successful as chemical and physical control methods (Meronek et al. 1996).

Pseudorasbora parva is able to carry a variety of harmful parasites and pathogens without showing any clinical signs of pathology. This suggests that utilizing parasites and pathogens as control measures is not practical and could have detrimental non-target effects (Ahne and Thomsen 1986; Harrell et al. 1986; Gozlan et al. 2010; Ercan et al. 2015; Andreou and Gozlan 2016).

Physical

Various types of physical controls that have been used to control other non-indigenous fish might also be effective in managing P. parva. Patrick et al. (1985) observed that air bubble curtains have been successful in deterring rainbow smelt, alewife, and gizzard shad—especially when used in conjunction with strobe lights. Other types of physical treatments have been employed in fish control include reservoir drawdowns, traps, nets, electrofishing, and combinations of these treatments. Through their review of fish control methods, Meronek et al. (1996) observed that projects that utilized nets were the most successful of the previously listed physical treatments, but P. parva’s small size (12–70 mm) make traditional physical removal methods, such as netting and electrofishing, difficult (Britton and Brazier 2006). Screening the main outfall of an invaded pond was shown to be ineffective in prohibiting the movement of < 20 mm individuals, therefore containment procedures must address all life stages of P. parva in order to effectively isolate and eradicate an introduced population (Britton and Brazier 2006). Small barriers may be effective at preventing the upstream dispersal of P. parva. In a flume study, a 7.5 cm barrier completely blocked the travel of P. parva (Jones et al. 2021).

Chemical

Of the four chemical piscicides registered for use in the United States, rotenone and antimycin have been used in the majority of chemical control projects and have had varied success rates for different species and different bodies of water (Marking et al. 1983; Boogaard et al. 1996; Meronek et al. 1996; GLMRIS 2012). Several studies have examined the effect of certain chemical agents on P. parva (Allen 2006; Britton and Brazier 2006; Saylar 2016). Allen (2006) determined that for eradication procedures, 0.15 mg L-1 is the lowest concentration of rotenone that will result in 100% mortality of P. parva over a 2-hour exposure period and 0.125 mg L-1 should be sufficient for exposure periods greater than or equal to 4 hours. The insecticide Permethrin has also shown to be lethal to P. parva at concentrations of 88.252 µg L-1 after a 96-hour exposure (Saylar 2016).

Note: Check state and local regulations for the most up-to-date information regarding permits for pesticide/herbicide/piscicide/insecticide use.