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What the sources say

Wels CatfishSilurus glanis

Every figure, record and mechanism on the Wels Catfish profile was written from a source, and this is the working table behind it: 55 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

FishBase

Silurus glanis Linnaeus, 1758. FishBase.

The page saysRecorded maxima of 2.73 meters and 130 kilograms
The source saysThe recorded maxima with evidence are 2.73 m and 130 kg
The page saysFor a long time, the wels catfish's recorded maximum stood at five meters and 306 kilograms
The source saysThe maximum length of the species has been recorded as 5 m for a long time and the maximum weight as 306 kg
The page saysFishBase says misidentifications and problems with measurement units produced those numbers
The source saysmisidentifications and problems of measurment units have led to these numbersNote: source typo 'measurment'
The page saysgives 2.73 meters and 130 kilograms as the maxima backed by evidence
The source saysThe recorded maxima with evidence are 2.73 m and 130 kg
The page saysFishBase puts the maxima backed by evidence at 2.73 meters and 130 kilograms
The source saysThe recorded maxima with evidence are 2.73 m and 130 kg
The page saysFor a long time the species' recorded maximum stood at 5 meters and 306 kilograms
The source saysThe maximum length of the species has been recorded as 5 m for a long time and the maximum weight as 306 kg
The page saysFishBase says misidentifications and problems with measurement units led to those figures
The source saysmisidentifications and problems of measurment units have led to these numbers

Source
02

Animal Diversity Web, University of Michigan

Silurus glanis (Danube catfish). Animal Diversity Web, University of Michigan.

The page saysLarge rivers, lakes, and deep water near dams, native to eastern Europe and Asia and introduced elsewhere in Europe, sometimes entering brackish water in the Baltic and Black Seas
The source saysnative to eastern Europe and Asia. It has been introduced to several other areas including Germany, France, Spain, England, Greece, Turkey and the Netherlands ... is found primarily in large rivers and lakes and in deep water near dams. These catfish sometimes enter brackish water in the Black Sea and Baltic Sea
The page saysFish, eels, crayfish, frogs, snakes, voles, rats, coypu, ducks
The source saysAt adult sizes they will also prey on ducks, voles, crayfish, fish, eels, frogs, rats, coypu, and snakesNote: pigeons: see the freshwater-2012 claims
The page saysMost individuals reach 1.3 to 1.6 meters and an average of 45 kilograms
The source saysMost individuals reach sizes between 1.3 and 1.6 meters. Silurus glanis reach an average of 45 kg
The page saysThe scaleless body is elongated, with a laterally flattened tail, and the fish prefers still water, usually over a soft bottom such as mud
The source saysThe elongated, scaleless body has a strong upper body and a laterally flattened tail ... prefers still waters, usually with a soft bottom like mud
The page saysThe wels catfish is most active at night
The source saysThese fish are most active at night
The page saysIt senses chemical cues with its barbels and olfactory buds, thought to be extraordinarily sensitive, and a lateral line system helps it detect water movement
The source saysindividuals use their barbels and olfactory buds to sense chemical cues in the water. They are thought to be extraordinarily sensitive to chemical stimuli. They also have a lateral line system that helps them detect water movement.
The page saysThe catfish takes prey in with the suction of a suddenly opened mouth, grips it with hundreds of soft, inward-sloping teeth on each jaw, and crushes it on two plates in front of the throat before swallowing
The source saysThey use the incredible suction created by suddenly opening their large mouths to take in prey. Both the top and bottom jaws each have hundreds of inward sloping, soft teeth used to grip prey. There are two "crushing plates" in front of the throat cavity used to crush prey before swallowing.
The page saysAdults prey on fish, crayfish, frogs, voles, rats, and ducks
The source saysAt adult sizes they will also prey on ducks, voles, crayfish, fish, eels, frogs, rats, coypu, and snakes.

Source
03

Cucherousset et al. 2012

Cucherousset et al. (2012). “Freshwater Killer Whales”: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLoS ONE.

The page saysEurope's largest freshwater fish
The source saysEuropean catfish Silurus glanis L., the world's third largest and Europe's largest freshwater fishNote: tagline; the 2012 paper's own words
The page sayson one French river, a hunter that beaches itself
The source saysFifty-four beaching behaviors with partial and mostly complete stranding were observed and filmedNote: beaching = the paper's 'partial and mostly complete stranding'; the river is the Tarn (see body claims)
The page saysto grab pigeons off a gravel island
The source saysa gravel island where pigeons ( Columbia livia Gmelin) regroup for drinking and cleaning
The page sayson one French river, pigeons
The source saysto capture birds on land (i.e. pigeons, Columbia livia )Note: the Tarn River study
The page saysA 2012 study calls Silurus glanis the world's third largest and Europe's largest freshwater fish
The source saysEuropean catfish Silurus glanis L., the world's third largest and Europe's largest freshwater fish
The page saysWels catfish were introduced to the Tarn River in southwestern France in 1983
The source saysWe conducted the present study in the Tarn River (Southwestern France) within the historical city center of Albi, a UNESCO World Heritage Centre. European catfish were introduced in the Tarn River in 1983
The page saysIn Albi, scientists filmed them lunging out of the water to seize pigeons on a gravel island
The source sayswithin the historical city center of Albi, a UNESCO World Heritage Centre. European catfish were introduced in the Tarn River in 1983 and have since established self-sustained populations [12] . Behavioral monitoring was performed from a bridge above a gravel island where pigeons ( Columbia livia Gmelin) regroup for drinking and cleaning
The page saysa behavior not reported in the species' native range
The source saysthis extreme behavior has not been reported in the native range of the species
The page saysOver 24 surveys they recorded 54 beaching attempts, and 15 of them, or 28 percent, caught a bird
The source saysDuring the 24 surveys conducted in an urbanized stretch of the Tarn River (France) ... Fifty-four beaching behaviors with partial and mostly complete stranding were observed and filmed (Movie S1), among which 28% (n = 15) were successful, i.e. the land birds were captured on landNote: 54 is 'Fifty-four' in the source
The page saysThe attacks were systematically triggered by active pigeons; motionless pigeons were never attacked, even very close to a catfish
The source saysThe attacks were systematically triggered by active pigeons. Indeed, motionless pigeons, even very closed to the European catfish, were never attacked.
The page saysAs the fish approached, they raised their upper jaw barbels, which the researchers say suggests they were detecting water vibrations rather than watching the bird
The source saysEuropean catfish were observed to exhibit erected upper jaw barbels on the upper jaw when they approach pigeons, suggesting that water vibrations, rather than visual cues, were used to detect and attack the prey
The page saysEach lunge lasted from less than a second to no more than four seconds, and in about 40 percent of observations the catfish had more than half its body out of the water
The source saysIn approximately 40% of all observations, European catfish had more than half of their body outside of the water. The beaching behavior was quick, lasting from less than one second to no more than 4 seconds.
The page saysand on the Tarn, pigeons
The source saysto capture birds on land (i.e. pigeons, Columbia livia )
The page saysEurope's Biggest Freshwater Fish
The source saysEuropean catfish Silurus glanis L., the world's third largest and Europe's largest freshwater fishNote: heading
The page saysOn the Tarn River in southwestern France, where the species was introduced, catfish strand themselves on a gravel island where pigeons gather to drink and clean
The source saysWe conducted the present study in the Tarn River (Southwestern France) ... European catfish were introduced in the Tarn River in 1983 ... a gravel island where pigeons ( Columbia livia Gmelin) regroup for drinking and cleaning
The page saysA strike takes no more than 4 seconds, and a caught bird is returned to the river and swallowed
The source saysreturned to the river and swallowed ... The beaching behavior was quick, lasting from less than one second to no more than 4 seconds
The page saysMotionless pigeons were never attacked
The source saysmotionless pigeons, even very closed to the European catfish, were never attacked
The page saysThe fish erect their upper jaw barbels on the approach, which the study reads as a sign they detect the prey through water vibrations rather than sight
The source saysEuropean catfish were observed to exhibit erected upper jaw barbels on the upper jaw when they approach pigeons, suggesting that water vibrations, rather than visual cues, were used to detect and attack the prey

Source
04

Pohlmann, Grasso & Breithaupt 2001

Pohlmann, Grasso & Breithaupt (2001). Tracking wakes: The nocturnal predatory strategy of piscivorous catfish. Proceedings of the National Academy of Sciences.

The page saysthe ability to track a prey fish's wake with no visible light
The source sayslocate a piscine prey (guppy, Poecilia reticulata) by accurately tracking its three-dimensional swim path before an attack in the absence of visible light
The page saysIn a 2001 lab study, catfish located a guppy with no visible light by tracking its three-dimensional swim path, following wakes up to 10 seconds old over distances up to 55 guppy body lengths
The source saysnocturnal European catfish (Silurus glanis) locate a piscine prey (guppy, Poecilia reticulata) by accurately tracking its three-dimensional swim path before an attack in the absence of visible light. Wakes that were up to 10 s old were followed over distances up to 55 prey-body lengths in our setupNote: 'in our setup' is carried by 'lab study'
The page saysWakes drew attacks from the rear, which the authors say may be harder for prey to detect
The source sayswakes elicit rear attacks, which may be more difficult to detect by prey
The page saysSwimming fish leave wakes holding hydrodynamic and chemical traces
The source saysSwimming fish leave wakes containing hydrodynamic and chemical traces.
The page saysIn a lab experiment with no visible light, catfish located guppies by tracking their three-dimensional swim path, following wakes up to 10 seconds old across as much as 55 guppy body lengths
The source sayslocate a piscine prey (guppy, Poecilia reticulata) by accurately tracking its three-dimensional swim path before an attack in the absence of visible light. Wakes that were up to 10 s old were followed over distances up to 55 prey-body lengths in our setup
The page saysFollowing a wake brought them in from behind, and the authors suggest rear attacks may be harder for prey to notice
The source sayswakes elicit rear attacks, which may be more difficult to detect by prey

Source
05

Bergström et al. 2022

Bergström et al. (2022). Exceptional longevity in northern peripheral populations of Wels catfish (Silurus glanis). Scientific Reports.

The page saysIn the species' core range, studies reviewed in 2022 put maturity at 4 to 7 years old and 70 to 100 centimeters long
The source saysPrevious studies have shown that catfish in these areas can reach a length of 70–130 cm within 5–7 years and become mature at 70–100 cm of length ... after becoming mature (at an age of 4–7 yearsNote: replaces ADW's single-study 3/4 years and FishBase's 86-108 cm, which disagree with each other; the 2022 review is the newer source
The page saysIn the core range, estimates suggest catfish very rarely live past 20 years
The source saysEstimates of longevity also suggest that catfish in these areas very rarely become older than 20 yearsNote: replaces ADW's older '20 to 30 years' expected wild lifespan, which the 2022 paper contradicts
The page saysThree native populations in southern Sweden are postglacial remnants, established 9,500 to 8,000 years ago
The source saysthree postglacial remnant populations (present in Lake Möckeln, River Emån and Lake Båven) in southern Sweden ... The northern peripheral populations of catfish were established in Sweden during warmer post glacial ages, 9500 to 8000 years ago
The page saysthey grow very slowly by comparison
The source saysrevealed very slow growth rates compared to catfish within the core distribution area
The page saysfish of about 175 centimeters are estimated to add around 2 centimeters a year
The source saysindividuals at a length of about 175 cm estimated to grow around 2 cm/year
The page saysA 15-year tagging study in two of those systems
The source sayswe conducted an extensive mark-recapture study across 15 years. Using a combination of fyke-nets and long-lining, we captured and tagged 1183 individuals ranging from 7 to 209 cm in two (out of three) of the Swedish systems inhabited by catfish
The page saysrecaptured a 195-centimeter catfish estimated to be 70 years old
The source saysthe largest recaptured individual (length 195 cm) was estimated to be 70 (95% CI 50–112) years old
The page saysabout twice the age of the oldest previously reported, a 33-year-old from Russia's Volga River
The source saysThe oldest previously reported catfish found was from the river Volga in Russia was 33 years and 266 cm long 22 , which is about half the estimated age of our largest recaptured individualNote: the paper's 'about half', inverted
The page saysIn 2022 the authors urged Swedish authorities to keep the closure of catfish fisheries that began in 1994
The source sayswe would like to strongly recommend authorities to maintain the closure of catfish fisheries in Sweden initiated in 1994Note: dated to the paper; no claim that it is still closed
The page saysThe Slow Giants of Sweden
The source saysDespite a large demand from the recreational fishery to target these giant fish in Sweden once againNote: heading; 'slow' is the paper's 'very slow growth rates'
The page saysIn the core range, estimates suggest wels catfish very rarely pass 20 years
The source saysEstimates of longevity also suggest that catfish in these areas very rarely become older than 20 years
The page saysIn southern Sweden, a 15-year mark-recapture study
The source sayswe conducted an extensive mark-recapture study across 15 years
The page saysestimated a 150-centimeter fish to be around 40 years old
The source saysThe fitted von Bertalanffy growth curve predicted a 150 cm catfish to be around 40 years old
The page saysits largest recaptured fish, 195 centimeters long, to be 70, with a 95 percent confidence interval of 50 to 112 years
The source saysthe largest recaptured individual (length 195 cm) was estimated to be 70 (95% CI 50–112) years old

Source
06

Cunico & Vitule 2014

Cunico & Vitule (2014). First records of the European catfish, Silurus glanis Linnaeus, 1758 in the Americas (Brazil). BioInvasions Records.

The page saysFar outside its native range, the species has even turned up in Brazil, where one was caught in a river in 2006 and another found dead in a pond beside a river in 2010
The source saysAlthough it originally inhabited rivers of Eastern Europe and Western Asia ... In August 2006, in the State of Santa Catarina, Southern Brazil ... the capture of a huge catfish by an amateur fisherman in the Itajaí-Açu River, which was identified as S. glanis . In March, 2010, the Laboratory of Ecology, Ichthyology and Fisheries (LEPI) of the Federal University of Paraná received another individual of S. glanis that had died in a small pond next to the Piquiri River

Source
07

Freyhof 2022

Freyhof (2022). Silurus glanis. The IUCN Red List of Threatened Species 2024: e.T40713A221242562.

The page saysIts 2022 IUCN Red List assessment lists the species as Least Concern
The source saysIUCN Red List category: Least Concern (LC).Note: reference is the 2024 assessment (DOI iucn.uk.2024-2)

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.