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 

P. 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). The Topmouth gudgeon’s life history traits are also highly plastic which facilitates the species’ adaptation to new environments and changing conditions (Beyer et al. 2007; Britton et al. 2008; Zahorska and Kovac 2009; Zahorska and Kovac 2013; Rosecchi et al. 2001). At low densities in invaded ecosystems,  P. parva tend to exhibit faster growth, earlier maturation, and higher fecundity (Britton et al. 2008; Zahorska and Kovac 2009) compared to high density populations or in its native range. P. parva also are 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 (Davies and Britton 2014; Britton et al. 2008; Katano and Maekawa 1997).

The Topmouth gudgeon’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. 2008). Once mature, P. parva will spawn in batches asynchronously during the spring and summer months, typically from April to August in its native range (Gozlan et al. 2010; Britton et al. 2008; Katano and Maekawa 1997). 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 (Pinder and Gozlan 2003; Britton et al. 2008; Zahorska and Kovac 2009; Zahorska and Kovac 2013; Katano and Maekawa 1997). 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 20 C (Pinder and Gozlan 2003).

Behavior of Topmouth gudgeon before, during and after spawning is thought to enhance reproductive success. Male Topmouth gudgeon 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).

P. 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). Topmouth Gudgeon will also feed opportunistically on floating objects and terrestrial insects (Pinder and Gozlan 2003). 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

The introduction and spread of Topmouth Gudgeon 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 is not known to 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).

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).

Pseudorasbora parva has 84 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 Diplostomum spataceum in Georgia (Kakalova and Shonia 2008), and viruses such as fry rhabdovirus (PFR) in Germany (Ahne and Thomsen 1986). 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 destruans (Gozlan et al. 2005, 2009, 2010; Witkowski 2011). These parasites if carried over after introduction could have destructive impacts on similar native Great Lakes species.

Pseudorasbora parva is one of the most (or the most) dominant species in fish assemblages where it is established (Kapusta et al. 2008, Tang et al. 2003). If introduced into the Great lakes, P. parva could cause noticeable stress or decline in at least one native population. Predator-prey relationships would be significantly adversely affected by the introduction of P. parva.

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. P. parva does carry parasites that are able to infect humans (Zhou et al. 2008, Pak et al. 2009, Xu et al. 2010, Bao 2012) but there are no documentations of P. parva directly transferring these to humans (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. 2008).

P. parva poses a threat to commercial and recreational fisheries. P. parva may outcompete native prey species and carry pathogens/parasites that are known to affect salmonids and Northern pike (Gozlan et al. 2010a). 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. P. 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 Psuedorasbora 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. P. parva has no economic value and it is only used by sport fishermen as bait fish (Lendhardt et al. 2011).

It is illegal to import, possess, deposit, release, transport, breed, buy, sell, lease or trade P. parva in Ontario (Invasive Species Act 2015). It is unlawful for any person to possess, import or sell live P. parva in Ohio (OH ADM. Code, 1501:31-19-01). In Michigan, it is illegal to possess, import, sell, or offer to sell P. parva (NREPA Part 413 as amended, MCL 324.41302). Illinois lists P. parva as an injurious species as defined by 50 CFR 16.11-15. Therefore P. parva cannot 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 from the Department of Natural Resources (17 ILL. ADM. CODE, Chapter 1, Sec. 805). This law also states that any interstate transporter is prohibited from transferring any injurious species from one container to another; nor can they exchange or discharge from a container containing injurious species without first obtaining written permission from the Department. The law also prohibits the release of any injurious species, including P. parva (17 ILL. ADM. CODE, Chapter 1, Sec. 805). Minnesota prohibits the possession, importation, purchase, sale, propagation, transportation, or introduction of P. parva (Minnesota Rule 6216.0250). There are no regulations on P. parva in New York, Pennsylvania, Indiana, or Wisconsin.

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). 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 (Kotov’ska 2011, Didenko and Gurbik 2011 in Tereshchenko 2016; Tereshchenko unpubl.). 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).

P. 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 (Gozlan et al. 2010; Ahne and Thomsen 1986; Andreou and Gozlan 2016; Ercan et al. 2015; Harrell et al. 1986).

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). 

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 (Boogaard et al. 1996; GLMRIS 2012; Meronek et al. 1996; Marking et al. 1983). 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.
 

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