Sheatfish, European Catfish

Silurus glanis feeds primarily at night, and it is well documented that S. glanis takes advantage of its diet plasticity and ability to prey upon the most abundant available species of a suitable size within its habitat (Carol 2009; Syväranta et al. 2010; Martino et al. 2011; Castaldelli et al. 2013). Trophic position increases with size, with the largest individuals acting as apex predators (Rees 2020). Its preference is for shrimp and crayfish in rivers, and shrimp and fish in streams, with largest specimens feeding primarily on fish(Ferreira et al. 2019). The fast growth and large size of S. glanis makes them unlikely prey for other piscivores (Copp et al. 2009).

Males and females mature at 2–3 years and 1–2 kg. Mating pairs spawn in April to June (up through September in northern latitudes > 41°N) at temperatures between 18 to 22°C. Spawning occurs in shallower waters, including drainage channels and floodplains (Kottelat and Freyhof 2007; Copp et al. 2009; Rees 2020). Eggs are laid in nests made of plant material and are defended by males until larvae emerge after 2–3 days (Kottelat and Freyhof 2007). Total fecundity can range from 30,000 to 300,000 eggs per female, and average relative fecundity ranges between 13,000 and 20,000 eggs per kilogram (Yazici et al. 2018; Yesilcicek 2020). Adults are known to live upwards of 80 years (Kottelat and Freyhof 2007).

Potential pathway(s) of introduction: Unauthorized Intentional Release

The import and sale of S. glanis to the United States was banned under the Lacey Act in 2016, however several hobbyist forums had posts seeking this fish since 2016, and one post indicated they had a specimen for sale in California, United States. As these claims cannot be verified, probability of introduction through this vector remains unknown. Due to the previous legality of their trade and extensive life span, an unknown number of specimens may still exist in the United States.

This species has been introduced to many European countries, including France, Italy, the Netherlands, Spain and the United Kingdom due to its popularity among anglers (Banarescu 1989; Krieg et al. 2000; Britton et al. 2007; Carol et al. 2007, 2009; Copp et al. 2009; Alp et al. 2011). This includes intentional, unauthorized introduction. Silurus glanis is farmed in Austria, Bulgaria, Croatia, Czech Republic, France, Hungary, Greece, Macedonia, Poland, and Romania (Linhart et al. 2002).

This species has spread rapidly through human introductions, but slowly via natural dispersal (Copp et al. 2009).  Introductions of S. glanis in Europe are facilitated by illegal stockings and natural dispersal intensified by climate change (Cerri et al. 2018; Rees 2020). The European Nonnative Species in Aquaculture Risk Analysis (ENSARS) listed S. glanis as a moderately low risk for introduction (but a moderate risk for establishment) in the UK, however a survey of anglers revealed a lack of awareness of the damages S. glanis will have if introduced (Copp et al. 2016; Rees et al. 2017). The Fish Invasiveness Screening Kit (FISK) listed S. glanis as a high risk of invasion in Croatia, Slovenia, and South Africa (Piria et al. 2016; Marr et al. 2017). The invasiveness of S. glanis is only expected to increase due to rising water temperatures from climate change (Rees 2020). As S. glanis encounters new environments, it is predicted to increase its use of space, which accelerates its dispersal rate (Cote et al. 2010; Chappele et al. 2012). Additionally, S. glanis individuals that have been translocated via traditional stocking methods were shown to have decreased fitness and altered behaviors (Monk 2020).

It is likely S. glanis would be able to survive in the Great Lakes since it tolerates a range of climates including many of the conditions found in the Great Lakes. Its mild salinity tolerance may give it a competitive advantage over native species limited to freshwater if salinization increases in the Great Lakes (Copp et al. 2009). Silurus glanis is able to adjust its diet based on availability of prey making it adaptable to Great Lakes food webs. This species is a nest guarder, which gives it an advantage over other native fish that do not nest guard young, and it has a long lifespan.

In countries currently invaded by S. glanis, spread and establishment can be rapid, particularly in the Iberian peninsula. Silurus glanis has spread via natural dispersal or stocking over 700 km in the River Tagus, Spain between their first introduction in 1998 and 2015 (Gago et al. 2016). Since 1974, S. glanis has spread into 6 of 7 of the watersheds in the Ebro basin, Spain, likely accelerated by angling activities and governmental water transfers (Parrando et al. 2018). Overall, the fishing effort and harvest of S. glanis has increased with angling and air temperature in Central Europe between 1986-2017 (Lyach and Remr 2019).

In early stage invasion sites, S. glanis mainly consumed fish because of a high abundance of small cyprinid species, such as Roach and Bleak (Carol et al. 2007). In contrast, crayfish was the main prey of catfish in advanced stage invasion sites and the ontogenetic shift to piscivory was delayed until the catfish grew larger. Accordingly, these advanced stage invasion reservoirs had size structures dominated by larger sizes of Common Carp. Although further data are needed to see how frequent these patterns are, the results strongly suggest that at the early stages of invasion, catfish grow faster and are in better condition because they prey more on fish. As invasion proceeds, however, the catfish reduce fish numbers, particularly of smaller fish, indirectly favoring crayfish and eventually resulting in their own reduced growth rates (Carol 2009).

In addition to fish prey, another likely ecological impact of catfish is on some groups of waterbirds, especially in the Anatidae family. A few birds have been observed in the catfish stomachs, (Omarov and Popova 1984, Czarnecki et al. 2003). Carol et al. (2009) also found that waterbird abundance varied significantly with the invasion sequence (advance stage correlated with lower bird abundance) and this did not appear to be correlated or confounded by abiotic factors (such as reservoir size, altitude or trophic state). The significantly lower abundance of waterbirds in reservoirs with catfish could be due to either a direct ecological impact (predation) by catfish and/or to avoidance behavior by waterbirds to reduce predation risk (Carol 2009).

Silurus glanis takes advantage of its diet plasticity and ability to prey upon the most abundant available species of a suitable size within its habitat (Carol 2009; Syväranta et al. 2010; Martino et al. 2011). If established as an apex predator in an ecosystem, S. glanis can heavily impact other species through predation and food web alterations (Vejrik et al. 2017a). Silurus glanis has even been reported to consume Atlantic salmon (Salmo salar) in France (Boulêtreau et al. 2017). In French rivers, an invasion of S. glanis impacted some fish communities, but not on a generalised basis as some rivers were productive enough to support both invasive species and natives (Guillerault et al. 2015). Silurus glanis may adapt foraging behaviors in new habitats and introduced populations have been observed to breach onto land to capture birds (Syväranta 2010; Cucherousset et al. 2012).

Silurus glanis has a growing list of associated parasites (Copp et al. 2009): Parasites in the family Myxobolidae, are known to infect S. glanis and can have a significant pathological impact on wild and cultured fishes. Such episodes of infection are often preceded by environmental stressors such as oxygen depletion (Lom and Dykova 1992). Acanthocephalans (L. plagicephalus), another common parasite of S. glanis, can cause extensive damage such as lesions to the intestinal tract of fish where they attach leading secondarily to infections by bacteria (Dezfuli et al. 1990). High intensities of parasitic crustaceans such as Ergasilus sieboldi can inflict severe damage to the gills (Dezfuli et al. 2003) resulting in large scale mortalities of fish (Kabata 1979). Silurus glanis is also subject to Aeromonas veronii infection, which is known to cause economic losses in aquaculture (Xiucai et al. 2019). The parasitic nematode Anisaki schupakovbia infects S. glanis, which when consumed by humans can cause anisakiasis (Abdybekova et al. 2020). Other known parasites include Triaenophorus crassus, Raphidascaroides sp., Lernaea cyprinacea (Khara et al. 2016), Lamproglena pulchella (Molnar et al. 2018), Sphaerospora siluri (Patra et al. 2018), Thaparocleidus vistulensi (Rees 2020), and mycoplasmas (Sellyei et al. 2020). Silurus glanis can carry the European sheatfish virus (ESV), a strain of ranavirus, which has been reported to also infect and be lethal to Zebrafish (Danio rerio), Pike (Esox lucius), and Pike-perch (Sander lucioperca) (Jensen et al. 2009, 2011; Martin et al. 2015).

Accumulation of heavy metals and chemicals such as PCBs and PAHs in S. glanis has been recorded above acceptable levels for human consumption and may be damaging to ecosystem health (Ivanovic et al. 2016; Milanov et al. 2016; Pastorino et al. 2016; Squadrone et al. 2016).

There is little or no evidence to support that Silurus glanis has the potential for significant socio-economic impacts if introduced to the Great Lakes.

Accumulation of heavy metals and chemicals such as PCBs and PAHs in S. glanis has been recorded above acceptable levels for human consumption and may be damaging to ecosystem health (Ivanovic et al. 2016; Milanov et al. 2016; Pastorino et al. 2016; Squadrone et al. 2016).

The parasitic nematode Anisaki schupakovbia infects S. glanis, which when consumed by humans can cause anisakiasis (Abdybekova et al. 2020).

Silurus glanis has the potential for high beneficial impact if introduced to the Great Lakes.

Silurus glanis has an economic importance in commercial and recreational fisheries as well as in aquaculture. Its aquaculture production has increased from 600 tonnes in 1993 to 2,000 tonnes in 2002 in ten European countries (Linhart et al. 2002; Copp et al. 2009). Fast and efficient growth, ease of breeding and rearing, and recent genome manipulation makes S. glanis ideal for commercial aquaculture (Copp et al. 2009; Cucherousset et al. 2018). Silurus glanis is considered a delicacy in some countries (Hungary, Poland, Slovakia, Lithuania), where it is exploited for its flesh (tender white meat), skin (for leather and glue production), and eggs (for caviar) (Copp et al. 2009). The flesh of S. glanis is highly nutritious in regard to fatty acid composition (Saliu et al. 2017; Linhartova et al. 2018) and protein quality (Pyz-Lukasik and Paszkiewicz 2018).The popularity of S. glanis relates to the large sizes they can reach; they are perceived as an attractive big-game species by many United Kingdom anglers (Hickley and Chare 2004). They are also a prized pet species, with specimens in the United States advertised for thousands of dollars.

The broad diet of S. glanis extends to species considered invasive to the Great Lakes, including Sea Lamprey (Petromyzon marinus) (Boulêtreau et al. 2020), Rudd (Scardinius erythrophthalmus), Tubenose (Proterorhinus semilunaris), Round (Neogobius melanostomus) and Monkey Goby (Neogobius fluviatilis), and Zebra mussels (Dreissena polymorpha) (Didenko et al. 2016; Mikl et al. 2017). They also consume European Perch (Perca fluviatilis) eggs, which were originally thought to be unpalatable to fish (Vejrik et al. 2017b).

Silurus glanis has value as a research and medicinal subject. Its environmental resilience and longevity make it useful for modeling the effects of parasites (Defzuli et al. 2017) and contamination of hexachlorobenzene and hexachlorobutadiene (Dosis et al. 2017). Further, S. glanis is an important model for investigating evolutionary dynamics of fish chromosomes (Ditcharoen et al. 2019).

Federally banned in the United States from import and trade under the Lacey Act. In Indiana (312 IAC 9-6-7), Michigan (Part 413 of Act 451), Minnesota (§ 84D.07), and Ohio (OAC 1501:31-19-01) Silurus glanis is prohibited, making it illegal to import, propagate, sell, buy, barter, trade, loan, or release into public or private waters in these states. It is also prohibited in the Canadian province of Manitoba (C.C.S.M. c. W65).

Control

Biological

There are no known biological control methods for this species.

Physical

Hook-lines and angling were an effective method of reducing S. glanis populations to harmless levels in two lakes in the Czech Republic (Vejrík et al. 2019)

Chemical

Shock treatment with saltwater (5% NaCl for 3 minutes) was fatal to some S. glanis larvae (Krasteva et al. 2020).

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.

Abdybekova, A.M., A.A. Abdibayeva, N.N. Popov, A.A. Zhaksylykova, B.I. Barbol, B.Z. Bozhbanov, and P.R. Torgerson. 2020. Helminth Parasites of Fish of the Kazakhstan Sector of the Caspian Sea and Associated Drainage Basin. Helminthologia 57(3):241-251.

Alp, A., C. Kara, F. Uckardes, J. Carol, and E. Garcia-Berthou. 2011. Age and growth of the European catfish (Silurus glanis) in a Turkish Reservoir and comparison with introduced populations. Reviews in Fish Biology and Fisheries 21(2):283-294.

Banarescu, P.M. 1989. Zoogeography and history of the freshwater fish fauna of Europe. Pages 88-107 in Holcik, J, ed. The freshwater fishes of Europe. Volume 1. Aula Verlag, Wiesbaden.

Borzym, E., T.A. Karpinska, and M. Reichert. 2015. Outbreak of ranavirus infection in sheatfish, Silurus glanis (L.), in Poland. Polish Journal of Veterinary Sciences 18(3):607-611.

Bouletreau, S., L. Carry, E. Meyer, D. Filloux, O. Menchi, V. Mataix, and F. Santoul. 2020. High predation of native sea lamprey during spawning migration. Scientific Reports 10:6122.

Bouletreau, S., A. Gaillagot, L. Carry, S. Tetard, E. De Oliveria, and F. Santoul. 2017. Adult Atlantic salmon have a new freshwater predator. PLoS ONE 13(4):e0196046.

Bouletreau, S., and F. Santoul. 2016. The end of the mythical giant catfish. Ecosphere 7(11):1-5.

Britton, J.R., J. Pegg, R. Sedgwick, and R. Page. 2007. Investigating the catch returns and growth rate of wels catfish, Silurus glanis, using mark–recapture. Fisheries Management and Ecology 14(4):263-268.

Capra, H., H. Pella, and M. Ovidio. 2018. Individual movements, home ranges and habitat use by native rheophilic cyprinids and non-native catfish in a large regulated river. Fisheries Management and Ecology 25(2):136-149.

Carol, J., L. Benejam, J. Benito, and E. Garcia-Berthou. 2009. Growth and diet of European catfish (Silurus glanis) in early and late invasion stages. Fundamental and Applied Limnology 174:317-328.

Carol, J., L. Zamora, and E. Garcia-Berthou. 2007. Preliminary telemetry data on the movement patterns and habitat use of European catfish (Silurus glanis) in a reservoir of the River Ebro, Spain. Ecology of Freshwater Fish 16(3):450-456.

Castaldelli, G., A. Pluchinotta, M. Milardi, M. Lanzoni, L. Giari, R. Rossi, and E.A. Fano. 2013. Introduction of exotic fish species and decline of native species in the lower Po basin, north-eastern Italy. Aquatic Conservation Marine and Freshwater Ecosystems 23:10.

Cerri, J., A. Ciappelli, A. Lenuzza, M. Zaccaroni, and A. Nocita. 2018. Recreational angling as a vector of freshwater invasions in Central Italy: perceptions and prevalence of illegal fish restocking. Knowledge and Management of Aquatic Ecosystems 419(38):10.

Chapple, D.G., S.M. Simmonds, B.B.M. Wong. 2012. Can behavioral and personality traits influence the success of unintentional species introductions? Trends in Ecology & Evolution 27(1):57-64.

Copp, G.H., J.R. Britton, J. Cucherousset, E. Garcia-Berthou, R. Kirk, E. Peeler, and S. Stakenas. 2009. Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges*. Fish and Fisheries 10(3):252-282.

Copp, G.H., M.J. Godard, I.C. Russell, E.J. Peeler, F. Gherardi, E. Tricarico, L. Miossec, P. Goulletquer, D. Almeida, J.R. Britton, L. Vilizzi, J. Mumford, C. Williams, A. Reading, E.M.A. Rees, and R. Merino-Aguirre. 2016. A preliminary evaluation of the European Non-native Species in Aquaculture Risk Assessment Scheme applied to species listed on Annex IV of the EU Alien Species Regulation. Fisheries Management and Ecology 23(1):12-20.

Cote, J., S. Fogarty, K. Weinersmith, T. Brodin, and A. Sih. 2010. Personality traits and dispersal tendency in the invasive mosquitofish (Gambusia affinis). Proceedings of the Royal Society B: Biological Sciences 277(1687):1571-1579.

Cucherousset, J., S. Boulêtreau, F. Azémar, A. Compin, M. Guillaume, and F. Santoul. 2012. Freshwater Killer Whales: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLoS ONE 7(12): e50840.

Cucherousset, J., P. Horky, O. Slavik, M. Ovidio, R. Arlinghaus, S. Bouletreau, R. Britton, E. Garcia-Berthou, and F. Santoul. 2018. Ecology, behaviour and management of the European catfish. Reviews in Fish Biology and Fisheries 28(1):177-190.

Czarnecki, M., W. Andrzejewski, and J. Mastynski. 2003. The feeding selectivity of Wels (Silurus glanis L.) in Lake Goreckie. Archives of Polish Fisheries 11(1):141-147.

Danek, T., P. Horky, L. Kalous, K. Filinger, V. Brichacek, and O. Slavik. 2016. Seasonal changes in diel activity of juvenile European catfish Silurus glanis (Linnaeus, 1758) in Bysicka Lake, Central Bohemia. Journal of Applied Ichthyology 32(6):1093-1098.

David, J.A. 2006. Water quality and accelerated winter growth of European catfish using an enclosed recirculating system. Water and Environment Journal 20(4):233-239.

Dezfuli, B.S., J.A. DePasquale, G. Castaldelli, L. Giari, and G. Bosi. 2017. A fish model for the study of the relationship between neuroendocrine and immune cells in the intestinal epithelium: Silurus glanis infected with a tapeworm. Fish & Shellfish Immunology 64:243-250.

Dezfuli, B.S., G. Grandi, P. Franzoi, and R. Rossi. 1990. Digestive tract histopathology in Acipenser naccarii (Bonaparte) from the Po River resulting from infection with leptorhynchoides plagicephalus (Acanthocephala). Rivista di idrobiologia 29:177-183.

Dezfuli, B.S., L. Giari, R. Konecny, P. Jaeger, and M. Manera. 2003. Immunohistochemistry, ultrastructure and pathology of gills of Abramis brama from Lake Mondsee, Austria, infected with Ergasilus sieboldi (Copepoda). Diseases of Aquatic Organisms 53(3):257-262.

Didenko, A.V., and A.B. Gurbyk. 2016. Spring diet and trophic relationships between piscivorous fishes in Kaniv Reservoir (Ukraine). Folia Zool 65(1):15-26.

Ditcharoen et al. 2019. Genomic Organization of Repetitive DNA Elements and Extensive Karyotype Diversity of Silurid Catfishes (Teleostei: Siluriformes): A Comparative Cytogenetic Approach. International Journal of Molecular Sciences 20:3545.

Dosis, I., M. Ricci, L. Majoros, R. Lava, H. Emteborg, A. Held, and H. Emons. 2017. Addressing Analytical Challenges of the Environmental Monitoring for the Water Framework Directive: ERM-CE100, a New Biota Certified Reference Material. Analytical Chemistry 89(4):2514-2521.

Ferreira, M., J. Gago, and F. Ribeiro. 2019. Diet of European Catfish in a Newly Invaded Region. Fishes 4(4):58.

Kottelat, M., and J. Freyhof. 2007. Handbook of European freshwater fishes. Publications Kottelat, Cornol, Switzerland.

Gago, J., P. Anastacio, C. Gkenas, F. Banha, and F. Riberio. 2016. Spatial distribution patterns of the non-native European catfish, Silurus glanis, from multiple online sources - a case study for the River Tagus (Iberian Peninsula). Fisheries Management and Ecology 23(6):503-509.

Greenhalgh, M. 1999. Freshwater Fish: The Natural History of Over 160 Native European Species. Mitchell Beazley, London, United Kingdom.

Guillerault, N., S. Delmotte, S. Bouletreau, C. Lauzeral, N. Poulet, and F. Santoul. 2015. Does the non-native European catfish Silurus glanis threaten French river fish populations? Freshwater Biology 60(5):922-928.

Hickley, P., and S. Chare. 2004. Fisheries for non-native species in England and Wales: angling or the environment? Fisheries Management and Ecology 11:203-212.

Ivanovic, J., J. Janjic, M. Baltic, R. Milanov, M. Boskovic, R.V. Markovic, and N. Glamoclija. 2016. Metal concentrations in water, sediment and three fish species from the Danube River, Serbia: a cause for environmental concern. Environmental Science and Pollution Research 23(17):17015-17112.

Jensen, B.B., A. K. Ersboll, and E. Ariel. 2009. Susceptibility of pike Esox lucius to a panel of Ranavirus isolates. Diseases of Aquatic Organisms 83:169-179.

Jensen, B.B., R. Holopainen, H. Tapiovaara, and E. Ariel. 2011. Susceptibility of pike-perch Sander lucioperca to a panel of ranavirus isolates. Aquaculture 313:24-30.

Kabata, Z. 1979. Parasitic Copepod of British Fishes. The Ray Society, London, United Kingdom.

Khara, H., and M. Sattari. 2016. Occurrence and intensity of parasites in Wels catfish, Silurus glanis L. 1758 from Amirkelayeh wetland, southwest of the Caspian Sea. Journal of Parasitic Diseases 40(3):848-852.

Krasteva, V., M. Yankova, and T. Hubenova. 2020. Salinity tolerance of European catfish (Silurus glanis Linnaeus, 1758) larvae. Bulgarian Journal of Animal Husbandry 57(3):48-53.

Kreig, F., A. Triantafyllidis, and R. Guyomard. 2000. Mitochondrial DNA variation in European populations of Silurus glanis. Journal of Fish Biology 56(3):713-724.

Lelek, A. 1987. Threatened Fishes of Europe. Page 343 in Juraj Holcík, ed. The Freshwater Fishes of Europe. AULA-Verlag. Aula Verlag, Wiesbaden.

Lelek, A., J. Libosvarsky, M. Penaz, R. Bezdek, and Z. Machacek. 1964. Observation on fish under ice in winter. Ekologia Polska 12:305-312.

Linhart, O., L. Stech, J. Svarc, M. Rodina, JP Audebert, J. Grecu, and R. Billard. 2002. The culture of the European catfish, Silurus glanis, in the Czech Republic and in France. Aquatic Living Resources 15 (2): 139-144.

Linhartova, Z., J. Kresja, T. Zajic, J. Masilko, S. Sampels, and J. Mraz. 2018. Proximate and fatty acid composition of 13 important freshwater fish species in central Europe. Aquaculture International 26(2):695-711.

Lom, J., and I. Dykova. 1992. Protozoan Parasites of Fishes. Page 315 in Developments in Aquaculture and Fisheries Science. Volume 26. Elsevier Scientific Publishing. Amsterdam, The Netherlands.

Lyach, R., and J. Remr. 2019. Changes in recreational catfish Silurus glanis harvest rates between years 1986-2017 in Central Europe. Journal of Applied Ichthyology 35(5):1094-1104.

Marr, S.M., B.R. Ellender, D.J. Woodford, M.E. Alexander, R.J. Wasserman, P. Ivey, T. Zengeya, and O.L.F. Weyl. 2017. Evaluating invasion risk for freshwater fishes in South Africa. Bothalia 47(2):1-10.

Martin, V., C. Mavian, A.L. Bueno, A. de Molina, E. Diaz, G. Andres, A. Alcami, and A. Alejo. 2015. Establishment of a Zebrafish Infection Model for the Study of Wild-Type and Recombinant European Sheatfish Virus. Journal of Virology 89(20):10702-10706.

Martino, A., J. Syvaranta, A. Crivelli, R. Cereghino, and F. Santoul. 2011. Is European catfish a threat to eels in southern France? Aquatic Conservation: Marine and Freshwater Ecosystems 21(3):276-281.

Massabuau, J., and J. Forgue. 1995. Les capacités d'adaptation du silure glane en hypoxie: un cas exemplaire d'homéostasie du milieu intérieur. Aquatic Living Resources 8:423-430.

Mikl, L., Z. Adamek, K. Roche, L. Vsetickova, L. Slapansky, and P. Jurajda. 2017. Invasive Ponto-Caspian gobies in the diet of piscivorous fish in a European lowland river. Fundam. Appl. Limnol 190(2):157-171.

Milanov, R.D., M.P. Krstic, R.V. Markovic, D.A. Jovanovic, B.M. Baltic, J.S. Ivanovic, M. Jovetic, and M.Z. Baltic. 2016. Analysis of heavy metals concentration in tissues of three different fish species included in human diet from Danube River, in the Belgrade Region, Serbia. Acta Veterinaria-Beograd 66:89-102.

Molnar, K., A. Avenant-Oldewage, B. Sellyei, A. Varga, and C. Szekely. 2018. Histopathological changes on the gills of asp (Aspius aspius) and European catfish (Silurus glanis) caused by Lamproglena pulchella and a Lamproglena sp (Copepoda: Lernaeidae), respectively. Journal of Fish Diseases 41:33-39.

Monk, C.T., B. Cheret, P. Czapla, D. Huhn, T. Klefoth, E. Eschbach, R. Hagemann, and R. Arlinghaus. 2020. Behavioural and fitness effects of translocation to a novel environment: Whole-lake experiments in two aquatic top predators. Journal of Animal Ecology 89(10):2325-2344.

Omarov, O.P., and O.A. Popova. 1985. Feeding behavior of pike, Esox lucius, and catfish, Silurus glanis, in the Arakum Reservoirs of Dagestan. Journal of Ichthyology 25:25-36.

Parrando, M., L. Clusa, Q. Mauvisseau, and Y.J. Borrell. 2018. Citizen warnings and post checkout molecular confirmations using eDNA as a combined strategy for updating invasive species distributions. Journal for Nature Conservation 43:95-103.

Pastorino, P., T. Scanzio, M. Prearo, C. Foglini, M. Righetti, L. Favaro, E.A.V. Burioli, B. Vivaldi, M.C. Abete, and S. Squadrone. 2016. Contaminants occurrence in the main allochthonous invasive species (Silurus glanis): an alert from Northern Italian freshwaters in Freshwater Invasives–Networking for Strategy (FINS-II).

Patra, S., P. Bartosova-Sojkova, H. Peckova, I. Fiala, E. Esterbauer, and A.S. Holzer. 2018. Biodiversity and host-parasite cophylogeny of Sphaerospora (sensu stricto) (Cnidaria: Myxozoa). Parasites & Vectors 11:347.

Phillips, R., and M. Rix. 1988. A guide to Freshwater Fish of Britain, Ireland, and Europe. Pan Macmillan Books Ltd, London, United Kingdom.

Piria, M., M. Povz, L. Vilizzi, D. Zanella, P. Simonovic, and G.H. Copp. 2016. Risk screening of non-native freshwater fishes in Croatia and Slovenia using the Fish Invasiveness Screening Kit. Fisheries Management and Ecology 23(1):21-31.

Placinta, S., M. Cretu, V. Cristea, and I. Grecu. 2020. The impact of environmental light on growth performance of juvenile catfish (Silurus glanis, L., 1758) reared in a recirculating aquaculture system. Scientific Papers: Series D, Animal Science-The International Session of Scientific Communications of the Faculty of Animal Science 63(2):458-463.

Pyz-Lukasik, R., and W. Paszkiewicz. 2018. Species Variations in the Proximate Composition, Amino Acid Profile, and Protein Quality of the Muscle Tissue of Grass Carp, Bighead Carp, Siberian Sturgeon, and Wels Catfish. Journal of Food Quality 1:2625401.

Rees, A. 2020. The impact of introduced European catfish (Silurus glanis L.) in UK waters: a three pond study. Unpublished Ph.D. dissertation. Hertfordshire University, Hatfield, England.

Rees, E.M.A, V.R. Edmonds-Brown, M.F. Alam, R.M. Wright, J.R. Britton, G.D. Davies, and I.G. Cowx. 2017. Socio-economic drivers of specialist anglers targeting the non-native European catfish (Silurus glanis) in the UK. PLoS ONE 12(6):e0178805.

Saliu, F., B. Leoni, and R.D. Pergola. 2017. Lipid classes and fatty acids composition of the roe of wild Silurus glanis from subalpine freshwater. Food Chemistry 232:163-168.

Sellyei, B., Z. Varga, G. Cech, A. Varga, and C. Szekely. 2020. Mycoplasma infections in freshwater carnivorous fishes in Hungary. Journal of Fish Diseases 00:1-8.

Squadrone, S., M. Prearo, R. Nespoli, T. Scanzio, and M.C. Abete. 2016. PCDD/Fs, DL-PCBs and NDL-PCBs in European catfish from a northern Italian lake: the contribution of an alien species to human exposure. Ecotoxicology and Environmental Safety 125:170-175.

Syvaranta, J., J. Cucherousset, D. Kopp, A. Crivelli, R. Cereghino, and F. Santoul. 2010. Dietary breadth and trophic position of introduced European catfish Silurus glanis in the River Tarn (Garonne River basin), Southwest France. Aquatic Biology 8:137-144.

Vejrík, L., et al. 2017a. European catfish (Silurus glanis) as a freshwater apex predator drives ecosystem via its diet adaptability. Scientific Reports 7:15970.

Vejrík, L., et al. 2017b. Thirty-Year-Old Paradigm about Unpalatable Perch Egg Strands Disclaimed by the Freshwater Top-Predator, the European Catfish (Silurus glanis). PLoS ONE 12(1):e0169000.

Vejrík, L., I. Vejrikova, L. Kocvara, P. Blabolil, J. Peterka, Z. Sajdlova, T. Juza, M. Smejkal, T. Kolarik, D. Barton, J. Kubecka, and M. Cech. 2019. The pros and cons of the invasive freshwater apex predator, European catfish Silurus glanis, and powerful angling technique for its population control. Journal of Environmental Management 241:374-382.

Wheeler, A. 1969. The Fishes of the British Isles and Northwest Europe. Michigan State University Press, East Lansing, MI.

Wolter, C., and A. Bischoff. 2001. Seasonal changes of fish diversity in the main channel of the large lowland River Oder. Regulated Rivers: Research & Management 17:595-608.

Wolter, C., and A. Vilcinskas. 1996. Fish fauna of the Berlinean waters -- their vulnerability and protection. Limnologica 26(2):207-213.

Wolter, C., and J. Freyhof. 2004. Diel distribution patterns of fishes in a temperate large lowland river. Journal of Fish Biology 64(3):632-642.

Xiucai, H., L. Xiaoxue, L. Aijun, S. Jingfeng, and S. Yajiao. 2019. Characterization and Pathology of Aeromonas veronii Biovar Sobria from Diseased Sheatfish Silurus glanis in China. Israeli Journal of Aquaculture-Bamidgeh 71:11.

Yazici, R., M. Yilmaz, and O. Yazicioglu. 2018. Reproduction Properties of Wels Catfish (Silurus glanis, L., 1758) Inhabiting Siddikli Reservoir. Journal of Limnology and Freshwater Fisheries Research 4(2):112-117.

Yesilcicek, T., and F. Kalayci. 2020. Fresenius Environmental Bulletin 29(4):2123-2133.