Chinese sleeper, rotan, Eleotris dybowskii Herzenstein & Warpachowski, 1878, E. pleskei Warpachowski, 1887, Perccottus glehni Dybowski, 1877

Nonindigenous Occurrences: Percottus glenni was first introduced to Europe in 1912 when several fish that were kept in an aquarium were released to ponds near St. Petersburg, Russia (Grabowska et al. 2010). It is considered one of the most invasive fish species in Europe in the past few decades (Copp et al. 2005; Piria et al. 2018). It is now found in Bulgaria (Reshetnikov et al. 2010), Croatia (Caleta et al. 2011), Germany (Reshetnikov and Schliewen 2013), Hungary (Reshetnikov 2004), Latvia (Pupina et al. 2015), Poland (Grabowska et al. 2011), Romania (Covaciu-Marcov et al. 2017), western and northern Russia (Reshetnikov 2003; Grabowska et al. 2011; Novoselov 2020), Serbia (Simonovic et al. 2006), eastern Slovakia (Košco et al. 2003), and Ukraine (Kvach 2012; Kutsokon et al. 2014). This species also occurs in the Vistula River (Grabowska et al. 2011), the Baltic Sea basin (Košco et al. 2003), and in the Black Sea (Kvach et al. 2021). This species has not been reported in North America.

Potential pathway(s) of introduction: Trans-oceanic shipping (ballast water)

Perccottus glenii does not currently occur near waters connected to the Great Lakes basin. This species is not known to hitchhike or foul recreational gear. Perccottus glenii is sold in Eurasia and was once a popular fish for aquariums and backyard ponds (Reshetnikov 2004).  It has been transported around Europe as a hitchhiker in stocked fish and from the aquarium trade, aquarium release, and natural dispersal via downstream migration (Kvach et al. 2017). Perccottus glenii often spreads during high water events where it moves from oxbow lakes and floodplains into adjacent rivers (Reshetnikov and Schliewen 2013). It is used as bait fish in Europe (Reshetnikov 2004; Edgar and Bird 2005). There is no evidence that this species can be obtained in North America to be released into the Great Lakes. Perccottus glenii is not cultured or stocked in the Great Lakes region. This species occurs in ports that have direct trade connections with the Great Lakes, such as those in the Baltic Sea (Košco et al. 2003; NBIC 2009). One of the suggested pathways for the introduction of Perccottus glenii is ballast water (Caleta et al. 2011). Perccottus glenii can tolerate a broad range of temperatures (Golovanova and Ruchin 2011) and waters with low oxygen (Reshetnikov 2003; Košco et al. 2008). Its tolerance to high salinity is not fully known, but it is likely that ballast regulations will substantially impact the survival of Perccottus glenii.

Perccottus glenii has a high probability of establishment if introduced to the Great Lakes (Confidence level: High).

The native and introduced ranges have a similar climate to the Great Lakes region and Mountain West (USFWS Ecological Risk Summary 2012). Perccottus glenii can tolerate a wide range of water temperatures (Golovanov and Ruchin 2011). Several studies mention that this species can tolerate low dissolved oxygen levels (Reshetnikov 2003; Košco et al. 2008; Caleta et al. 2011; Yang et al. 2012), but no specific ranges are reported. The optimal salinity for this species is 0–6 ppt (Golovanov and Ruchin 2011) and it inhabits fresh to brackish water (Froese and Pauly 2010). Perccottus glenii is also resistant to high water eutrophication (Košco et al. 2003). Given its tolerance to a wide variety of environmental conditions, it is likely that this species can establish in the Great Lakes, especially in stagnant water bodies of a shallow depth. This species is known to overwinter under frozen bodies of water, and hibernates in mud (Košco et al. 2008; Karanova 2009; Golovanov and Ruchin 2011), thus it is likely that this species can overwinter in the Great Lakes. Perccottus glenii will likely adapt to the effects of climate change in the Great Lakes, including warmer water temperatures, shorter duration of ice cover, and increased salinization. Perccottus glenii may also benefit from the “enemy release hypothesis”, which states that low parasite loads in non-native species may support establishment and expansion (Kvach et al. 2020).

Perccottus glenii feeds opportunistically, preying on animals at every trophic level, and is omnivorous (Reshetnikov 2003; Košco et al. 2008; Grabowska et al. 2009). This species has the potential to compete with native species (Košco et al. 2003; Reshetnikov 2003; Orlova et al. 2006). In addition, there are species in the Great Lakes region that may prey on Perccottus glenii such as Perch and Pike (Golovanov and Ruchin 2011), but little research has been conducted to investigate whether these predators will reduce this species’ probability of establishment.

Its average fecundity ranges 7,766–9,149 eggs per female, which increases with increasing size (Grabowska et al. 2011). Perccottus glenii is an aggressive nest guarder and tends the fertilized eggs until hatch (Bogutskaya and Naseka 2002). The fecundity of Perccottus glenii is higher than that of native nest-guarders, but lower than fishes not exhibiting parental care. Individual growth rates are higher in the Vistula River than in its native range (Grabowska et al. 2011). Life history characteristics such as short max body length and reproductive strategies (e.g., early maturation, multiple spawning events, extended breeding season, and parental care) are attributed to P. glenii being one of the most successful non-native invaders in Europe (Grabowska and Przybylski 2015; Natase and Novadaru 2019).

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

Environmental	Socioeconomic	Beneficial

Perccottus glenii is a host to some parasites. Data suggests that parasites Myxidium rimskykorsakowi, Henneguya alexeevi, Nippotaenia mogurndae, Goussia obstinata, Amurotaenia percotti, and Gyrodactylus perccotti were introduced to new regions with P. glenii as a vector (Sokolov et al. 2014; Kvach et al. 2016); these parasites infect fishes in the Odontobutidae family. Notably, G. percotti is unable to survive on non-gobiid hosts longer than 24 hours and therefore is unlikely to represent a threat to non-gobiid fishes in non-native ranges (Ondracková 2016). Perccottus glenii specimens released from aquariums are often infected with parasites common in aquaria (Sokolov 2018). It is known to host the copepod Neoergasilus japonicus, which is currently found in the Great Lakes (Kvach et al. 2020). This species also is a host to the diplomonad Spironucleus salmonis (Denikina et al. 2019), which can cause systemic spironucleosis in wild salmon and has been linked to significant aquacultural damage (Jorgensen and Sterud 2006; Williams et al. 2011) However, none of these events have been directly linked to Perccottus glenii. A full list of parasites in non-native Perccottus glenii populations can be located in Sokolov and Reshetnikov (2020).

As a trophic competitor and a predator, Perccottus glenii has been implicated in the population declines of historically abundant native species such as Umbra krameri, Carassius carassius, and Leucaspius delineatus (Košco et al. 2003). In laboratory experiments, Perccottus glenii reduced the foraging efficiency of Umbra krameri through aggressive interactions, resulting in a feeding rate one third of that found in the control (Grabowska et al. 2019).  Habitats with high numbers of Perccottus glenii were associated with lower fish species richness and diversity. Perccottus glenii can potentially compete with native species that utilize similar microhabitats and food resources (Košco et al. 2003). Perccottus glenii’s piscivory and high food competition resulted in a monospecific community in a Latvian marsh (Kutsokon et al. 2021).

By feeding heavily on macroinvertebrates, larval and adult amphibians, and fish eggs, Perccottus glenii has the potential to alter predator-prey relationships (Reshetnikov 2003). Many aquatic larvae of terrestrial organisms are primary consumers and export nitrogen from the system when leaving the water at maturity, which is meaningful for nitrogen dynamics and the rate of eutrophication. Perccottus glenii effectively reduces the transport of nitrogen from aquatic to terrestrial environments by feeding on these organisms.

Perccottus glenii has the potential for low socio-economic impact if introduced to the Great Lakes.

Perccottus glenii is a host to the liver fluke, which is a parasite that infects humans (Mastitsky et al. 2010), but there are no reports suggesting that Perccottus glenii is responsible for liver fluke infection in humans. It is also a host to the diplomonad Spironucleus salmonis (Denikina et al. 2019), which can cause systemic spironucleosis in wild salmon and has been linked to significant aquacultural damage (Jorgensen and Sterud 2006; Williams et al. 2011). However, none of these events have been directly linked to Perccottus glenii. There is no indication that this species impacts water quality, markets, or infrastructure. There is no evidence suggesting that it inhibits recreation or diminishes the natural value of the areas it inhabits.

Perccottus glenii has the potential for moderate beneficial impact if introduced to the Great Lakes.

Small introductions of Perccottus glenii in Eurasia were attempted in effort to reduce mosquito populations with no significant results (Košco et al. 2003). This species can be used as a bait fish and is sometimes kept in ponds or aquariums (Reshetnikov 2004; Košco et al. 2008). In the 2000s, populations of Perccottus glenii in the middle and upper Ob basin reached such high densities that this species became a significant catch for commercial fisheries (Reshetnikov et al. 2017). There is no indication that Perccottus glenii is valuable for medical research, for removing toxins, or for positively impacting the ecosystem.

In the United States, Perccottus glenii is included on the current list of injurious wildlife under the Lacey Act. In Minnesota, the possession, importation, purchase, transport, or introduction of Percottus glenii is a misdemeanor unless under a permit for disposal, control, research, or education (§ 84D.07). In Ohio, it is unlawful for any person to possess, import or sell live individuals of this species (Ohio Administrative Code 1501:31-19-01).

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

Control

Biological

Biocontrol of invasive P. glenii populations was successful (complete eradication in four small (1.1–11.7 ha) Lihuanian lakes using stocked native fish, Esox lucius and Perca fluviatilis after 5 years (Rakauskas et al. 2020).

Physical

There are no known physical control methods for this species. 

Chemical

There are no known chemical control methods specific to this species. General piscicides (such as rotenone) may be used for control, but expect significant kill of non-target species.

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.