European catfish

from Wikipedia, the free encyclopedia
European catfish
Silurus glanis 02.jpg

European catfish ( Silurus glanis )

Systematics
Cohort : Otomorpha
Sub-cohort : Ostariophysi
Order : Catfish (Siluriformes)
Family : Real catfish (Siluridae)
Genre : Silurus
Type : European catfish
Scientific name
Silurus glanis
Linnaeus , 1758

The European catfish or catfish ( Silurus glanis ) is the largest pure freshwater fish in Europe and next to Aristotle catfish ( Silurus aristotelis ), the only European Art from the family of genuine catfish (Siluridae). Regionally it is also referred to as catfish or sheepfish and with numerous variations of these names. Catfish are primarily nocturnal and crepuscular predatory fish that feed on live and dead fish, but also on invertebrates and occasionally on small water birds and mammals. Their activity in the course of the year is heavily dependent on the temperature and the availability of prey and reaches a maximum in spring after hibernation and in late autumn after spawning .

The distribution area of ​​the catfish stretches from Central and Eastern Europe to Central Asia. Large rivers and lakes with a muddy bottom are preferred. However, catfish are also often found in lakes with a low salt content, such as the Caspian Sea , as well as in brackish water areas of inland seas, such as in parts of the Baltic Sea and the Black Sea . The species has been fished since ancient times and is of economic importance today, especially in Eastern Europe, where it is increasingly being drawn into aquaculture . In Central Europe, on the other hand, catfish are mainly popular with anglers as sport fish and have therefore been settled in various areas in which they were not originally found. Today the stocks are mostly stable, but partly dependent on stocking by humans.

etymology

The catfish was first scientifically described by Carl von Linné in 1758 as Silurus glanis . It is the type species of the genus Silurus , which in turn gives its name to the family of the real catfish (Siluridae) and the order of the catfish-like (Siluriformes). Both “Silurus” and “glanis” are Latin names for the catfish. The German names “Wels” and “Waller” and their regionally used modifications probably go back to the same linguistic root as the word “ Wal ”, which originated from the Germanic “hwalaz”, related to the Latin “squalus” (“a larger sea fish, perhaps the sea fish ") and the old Prussian " kalis "(" catfish "). The catfish could have been seen as a small freshwater whale. The designation as "Schaiden" or "Schaidfisch", in Eastern Austria also as "Scharn" or "Scharl", has been proven as "sceida" since Old High German , but its origin is unclear.

features

Catfish from the front with clearly recognizable barbels
Albinotic "white catfish"

The catfish are stocky fish with an elongated body, a large, broad head and smooth, slimy and completely flake-free skin. The trunk is strongly built in the front area and round in cross-section, laterally flattened and slimmer behind the anus . The number of ribs is 72 to 74. A fully developed lateral line runs along the flanks and has 70 to 75 canals. The head makes up more than 20 percent of the total length and is wide and flattened with small eyes that sit laterally behind a pair of long, cartilage-reinforced and highly mobile barbels on the upper jaw. Two pairs of shorter, immobile barbels sit on the chin. The front nostrils stand out clearly and lie between them at the level of the maxillary barb. The posterior nostrils are close behind and are well developed, which indicates a good sense of smell . The mouth is large, wide and terminal with - especially in older animals - protruding lower jaw and fleshy lips. The teeth are small, flat and rearward-facing brush teeth. They sit in the lower jaw in four or five rows, which are divided in the middle by the jaw suture. Teeth are also located on the palate and ploughshare as well as on the gill arches , where they are particularly small. The gill opening is large and deeply slit, its membranous edge covers the base of the pectoral fins. The ventrally overlapping Branchiostegalmembranen have 15 to 16 Branchiostegalstrahl , the gill trap twelve thorns.

The dorsal fin is very small and sits at the end of the first third of the body. It has one hard jet and three to four soft rays. There is no adipose fin . The pectoral fins are large and strong and reach the base of the pelvic fins . They have a hard jet, the front side of which is smooth and the rear edge toothed, and 14 to 17 soft rays. The significantly smaller pelvic fins have 11 to 13 soft rays. The anal fin is elongated on the strongly elongated caudal peduncle and has 84 to 92 strong soft rays. It reaches close to the relatively small, rounded and almost straight cut off at the end, 17- to 19-rayed caudal fin - but the two fins are not connected.

The coloration is relatively variable and mostly adapted to the habitat so that resting catfish are well camouflaged. The upper side of the body is usually dark with a gray basic color, which can vary from blackish or blue-black to dark brown to dark olive green. The sides are lighter with an occasional purple sheen. Over the basic color there is usually a cloudy to dot-like marbling. The head is darker in color and shiny in one color, the lip edge can be lighter. The belly is light to whitish, sometimes slightly reddish and can be monochrome or piebald. The paired fins are usually dark yellow-brown, brownish-red to brownish, the unpaired fins shimmering bluish and purple. In addition to the normally colored animals, there are also monochrome black-blue or albinotic individuals.

Gender differences

Catfish do not show any noticeable sexual dimorphism . The males are usually a little longer at the same age, while older animals have a more angular upper jaw. The females are heavier and have a significantly swollen abdomen , especially before spawning . In the male, the anal opening is narrower with a pointed, slightly wrinkled genitalia. The female genus is more oval, swollen and ends rounded.

size

Large caught catfish, the area with the brush teeth can be seen in the mouth behind the lower lip

Depending on their habitat, catfish usually reach a length of one to one and a half meters and a weight of around 10 to 50 kilograms. Since the animals grow throughout their life, however, they can also become significantly larger and heavier. The information about the maximum dimensions differ considerably from different authors. Today, a length of up to three meters and a weight of 150 kilograms are often given. However, there are reports of significantly larger animals from the eighteenth and nineteenth centuries. Catfish up to five meters long and weighing more than 300 kilograms were reported in the Dnepr in the Ukraine , and an animal weighing 375 kilograms, weighed without viscera, is said to have been caught in the Oder in 1731 . These dimensions have been adopted by some authors to this day and are often provided with the comment that animals of this size no longer exist today. The largest and most reliably documented fishing rods were an animal weighing 144 kilograms and 2.78 meters long from the Po and a 148 kilogram specimen that was caught in Bulgaria. This makes the catfish the largest fish in Europe that constantly lives in freshwater . It is only surpassed by the sturgeon ( Acipenser ), which, however, are anadromous migratory fish that only enter rivers to spawn.

Age can be determined from the growth rings of the vertebrae or pectoral fin rays. The highest documented age is 60 years in captivity and 80 years for a wild animal. Estimates for the maximum possible age are around 100 years.

Internal anatomy and molecular biology

The strong, muscular throat is followed by a highly flexible stomach , which is divided into three successive sections. The intestine has three coils, the total length of the digestive tract exceeds the length of the body. The liver is relatively large. The swim bladder extends over about 80 percent of the body cavity and is therefore noticeably large. It has a longitudinal septum, is connected at the rear end to the spine and to the hearing organs via Weber's apparatus, which emerges from the rib bones . The sex glands are relatively small and are located in the back of the abdominal cavity.

The chromosome set consists of 30 pairs (2n = 60).

Occurrences and stocks

Distribution area of ​​the catfish.
  • Original distribution area
  • Coastal occurrences
  • occurrences established by humans

    • The original distribution area of ​​the catfish stretches from the Elbe and Doubs in eastern France through southern Sweden, eastern and southeastern Europe (with the exception of the Mediterranean coast) and Turkey to the Aral Basin and Afghanistan . In the river system of the Rhine it occurs naturally up to the mouth of the Ill near Strasbourg . However, subfossil finds indicate that the species was formerly also found further north in the Rhine and its tributaries up to the confluence with the North Sea. A possible remnant of this earlier distribution is the population in the Haarlemmermeer in the Netherlands. In addition to standing and flowing fresh waters inland, it is also found in the Caspian Sea and in brackish water areas of the Baltic Sea and the Black Sea .

    The species was also released by humans as aquaculture and sport fish outside of its natural range, for example in Spain, Italy and Kazakhstan. It was successfully resettled in the Benelux countries and France, even in areas where it cannot be archaeologically proven, for example in France from 1857 in the area of ​​the Rhone . In the south of Great Britain catfish were released in lakes from 1880 onwards, but the colonization of larger rivers was hardly possible, probably due to climatic conditions. In southern Finland and possibly also in Denmark, the released stocks have been wiped out again. In some regions where the catfish was originally absent, it is now viewed as a pest as it threatens local fish stocks.

    The species is generally not considered to be threatened, but the populations are partly dependent on stocking by humans, as the spawning grounds are often threatened by the expansion of rivers. In the north-west of the range, particularly in southern Sweden, the number of catfish is declining due to unfavorable climatic conditions and less suitable habitats. In northern Greece, where the species occurs naturally in individual lakes, individual populations have been displaced by competition with other exposed species such as the Aristotle catfish ( Silurus aristotelis ). In the Bern Convention , the catfish is listed in Appendix III as a protected species.

    Systematics and evolution

    Within the genus Silurus , the European catfish can be assigned to the European-West Asian glanis group, which is compared to the East Asian cochinchinensis group. The sister taxon could be Silurus triostegus , with which it shares the smooth front of the pectoral fin hard ray . However, there are no recent molecular biological studies on the relationships. No subspecies are distinguished within the species Silurus glanis .

    The origin of the genus Silurus is probably in Asia, from where it penetrated westward via the Caspian and Black Seas, Dnepr , Volga and Danube . In the case of the European catfish, the populations of different regions show only relatively minor genetic differences, which indicates that the species spread from a single refuge , probably in the Volga region, after the Ice Ages . The oldest fossil finds assigned to the European catfish are around 8,000 years old.

    Habitat

    Bank area of ​​the Volga Delta with rich vegetation of aquatic plants

    Catfish are heat-loving fish that prefer to live in large, stagnant or slow-flowing waters. Brackish water areas in estuaries or near the coast are populated up to a salinity of 15 ‰. They prefer shallow water areas up to a maximum depth of about 30 meters. The animals are relatively insensitive to pollution and low oxygen concentrations . Due to the high hemoglobin content of 30 to 35% in the blood, catfish are able to survive even at low oxygen concentrations of up to about 3 mg / l. Their physiological optimum temperature is 25 to 27 ° C, but significantly lower water temperatures are also well tolerated, although growth can be restricted. Adult animals prefer quiet areas overgrown with aquatic plants and are faithful to their location and probably territorial loners. Young fish in the first year, on the other hand, also stay in the middle, flowing area of ​​rivers and can be found in groups.

    Way of life

    activity

    Catfish are light-shy and predominantly nocturnal, although the activity patterns can differ significantly depending on the season. They are also active during the day, especially when the air pressure drops, which is perceived with the help of the swim bladder; otherwise the animals usually rest on the ground between water plants, under overhanging banks or tree roots until dark. The animals stop feeding when the water temperature is between seven and four ° C. They overwinter in rivers in crevices or pits near the bank, in lakes in the lower third of the water column or lying on muddy ground.
    Between May 2009 and February 2011 catfish with atypical behavior were observed in the Rhone : the normally solitary animals were found in groups that included up to 44 large specimens (largest observed length: 2.10 meters). On the one hand, it was not a matter of swarming, as the swimming movements were uncoordinated and the animals sometimes collided, and on the other hand, it could be ruled out that the catfish were trying to reproduce, search for food or protect themselves from attackers. These groups achieved a biomass density of up to 40 kilograms per square meter of river bed.

    Diet and catching of prey

    Head of an albinotic catfish with well recognizable barbels
    A catfish attacks pigeons sitting on the bank out of the shallow water.

    Catfish are opportunistic predatory fish that prey on almost anything that can be managed in terms of size. The largest share is usually made up of those fish that dominate the corresponding body of water, such as tench , roach or carp . In addition to live and dead fish, amphibians , crustaceans , insects , worms and other invertebrates, young water birds and pigeons as well as occasionally plants and mammals, especially rodents, are eaten. Compared to other large freshwater predatory fish such as pike or pikeperch , large catfish eat prey of very different sizes, which leads to more effective use of the food supply. For this reason, catfish have less of an impact on the population of economically important fish species.

    Most of the prey is caught at night, with eyes unlikely to play a role. Catfish have an excellent sense of smell and taste, which includes receptors for sweet, sour, bitter and salty, which are located in the mouth, on the lips, on the barbels, but also on the fins and in the skin of the head and front body . The hearing of the animals is extremely sensitive and specializes in noises from above the surface of the water, which is achieved by connecting the swim bladder with the hearing organs via Weber's apparatus emerging from the rib bones . This is also made use of by sport fishermen, who use a paddle on the surface to generate special noises that can attract catfish. In addition, catfish have electroreceptors and a pronounced sense of touch, which is based on the barbels, the lower jaw and the lateral line organ. Prey fish are mostly tracked and captured from behind, using chemical and hydrodynamic signals in the wake of fleeing fish for orientation.

    Food intake is heavily dependent on the water temperature. While almost no food is consumed from November to March, a phase of more intensive food intake begins with the higher availability of prey in spring. In June and July, many fish migrate to deeper waters, so that the catfish are less prey. After the spawning season in August, there is another high point in food consumption.

    Reproduction and development

    The spawning time of the catfish depends on the water temperature and usually begins when it has risen to 17 to 18 ° C. In Hungary it begins at the beginning of April, in Central Europe it usually falls between May and July. The male prepares a spawning place by flushing a pit near the bank, usually 40 to 60 centimeters deep and often protected by willow roots , with strokes of the tail and pressing soft plant material with his mouth to the ground. Here it is waiting for a suitable female. The act of spawning is preceded by a stormy foreplay in which the male pursues his partner near the surface of the water. The mating usually takes place in the evening hours at water temperatures of 22 to 23 ° C. The male swims around the female, drives it around the nest and hits its stomach with its mouth. Above the nest, the male swims to the side of the female and winds around her belly. After a few seconds the female frees herself, sinks to the bottom and releases the eggs, followed by the male's sperm release. The entire process is repeated several times over the course of one and a half to two hours. The amount and size of the eggs vary with the nutritional status and the size of the female; around 20,000 to 25,000 eggs with a diameter of 1.4 to 2 millimeters are produced per kilogram of body weight. After fertilization, the eggs swell and can reach a diameter of 4.5 millimeters by the time they hatch. They are very sticky and form large lumps that are difficult for water to penetrate, which can lead to poor oxygen supply and fungus. The male may therefore stay with the clutch until the brood hatch, guard it and fan it with fresh water every three to five minutes with the caudal fin.

    The tadpole-like larvae hatch after two to three days, depending on the water temperature. Immediately after hatching, the offspring are largely helpless and sink to the bottom of the water, after another two to three days the animals begin to actively move. They are very sensitive to light, die in direct sunlight and seek out dark areas of water whenever possible. The yolk sac is used up after about ten days of life; From this point on, the larvae begin to look for food on the bottom but also in open water. At the beginning they feed mainly on zooplankton , later the food spectrum is expanded to include crustaceans , insect larvae, small snails and Tubifex . After about twenty days the larval features begin to disappear; At this point the young catfish have reached a length between 2.2 and 2.5 centimeters. From a body length of 2.5 to three centimeters, they begin to chase other fry. If there is a lack of food, cannibalism occurs among the catfish offspring , which increases if the shortage continues. Plant detritus is also consumed in certain quantities depending on the availability of food. In general, however, invertebrates make up the vast majority of the food consumed in the first year of life.

    Catfish grow up quickly and in the first year they reach an average length of 20 to 30 centimeters, a maximum of almost half a meter and a weight of up to 500 grams. At the age of two, an average of 40 centimeters is reached and one meter at around six to seven years. Most of the growth takes place in spring, depending on the temperature and diet. Therefore, the growth rates in different regions of the range vary significantly depending on the climate. Sexual maturity is reached at a weight of one to two kilograms at around three to four years of age, but in cold climates it takes around nine years. As you reach sexual maturity, the rate of increase in length decreases, while the relative weight gain increases. Overall, the growth rates in males in terms of length and weight are higher than in females.

    Diseases and parasites

    Fish louse around 4 mm in size

    Various diseases and parasites in catfish are known from studies on wild-caught fish and, above all, from observations in aquaculture. Eggs in particular are susceptible to bacteria , fungi , parasites and losses from aquatic insects such as beetles , bed bugs and dragonfly larvae . Adult animals are hosts to a variety of bacteria, including flavobacteria and species from the genera Aeromonas and Vibrio . More than 50 different types of eukaryotic parasites have been described, including various single-cell organisms such as Apicomplexa , but also roundworms , tapeworms and fish lice . In catfish breeding, the greatest losses are due to ichthyophthiriosis . A species-specific virus , the "European sheatfish virus" (ESV) from the genus Ranavirus in the Iridoviridae family , was described in 1989. In addition, the species is also susceptible to viruses from the Rhabdoviridae family such as the spring viremia pathogen in carp . In the wild, diseases and parasite infestations play a role, especially as a result of environmental stress such as pollution or lack of oxygen, while in aquaculture, whole young fish that are cultivated can sometimes become ill and die.

    Cultural meaning and use

    Historical catfish illustration from 1886

    Due to its size and striking shape, the catfish is a well-known food fish that has found its way into sagas and legends, especially in Eastern Europe. Its meat and fat were used for healing purposes in some places. In the fourth century it was referred to by the Roman poet Decimus Magnus Ausonius as nostrae mitis balaena Mosellae ("gentle whale of our Moselle"). Conrad Gessner took up this formulation in his fish book and wrote that this fish could - according to a contemporary translation - "be called a German whale fish". At the same time, however, Gessner also commented that the catfish is a “very hideous, large, harmful fish” and, citing traditional finds of human bones in the stomach of catfish, ascribed it “a tyrannical, grim and gnawing species”. It is questionable whether Ausonius actually meant the catfish in his text. In the original text, the word silurus is used for the fish , but translators have identified the fish mentioned as a sturgeon based on the behavior described (wandering movements) .

    Exceptionally large catches have been reported in the media, as well as attacks on pets. In 2001 the modern legend about the alleged catfish "Kuno" found in the Volksgarten pond near Mönchengladbach , which was claimed to have eaten a young dachshund. In 2012 it was reported that a catfish attacked a young person in a bathing lake in Austria.

    Young catfish can also be kept well in cold water aquariums , whereas larger animals are more sensitive and are only suitable for large show aquariums. For these, albinotic catfish are specifically bred. The economic importance of the catfish is different in the different regions of its range. It is commercially fished in Eastern and Southeastern Europe and is increasingly being drawn into aquaculture . Its meat is white, has a mild taste, has few bones and a fat content of six to eight percent. It is marketed fresh, dried, smoked or salted. The eggs are sometimes used as caviar in the Caspian Sea . The swim bladder and bones can be made into glue or gelatine, the skin into leather. In Central Europe, on the other hand, it is often considered a potential pest that reduces the economically used carp and tench stocks. However, since it mainly eats economically insignificant fish, its influence on the fish stocks can also be positive. Catfish were occasionally used for the biological control of carp fish , for which they are less suitable than other predatory fish due to their relatively wide range of prey.

    fishing

    Angler with caught catfish
    Commercial catfish fishing
    In the Danube region, catfish have been fished using various methods since at least the second century. For this purpose, contact nets were mostly used, which consist of a base part and two wings connected to a rod and which could be lifted out of the water when in contact with the fish. Alternatively, a hollow tree trunk was sunk as a possible shelter and regularly lifted out of the water and checked. In addition, underwater fences were used, in which the catfish were driven into passages, where they were caught with a trap or by a fisherman equipped with a chisel . Catching with a line and hook, often with beef as bait, and hat fishing were also common, with the latter specifically looking for shelter near the shore. The modern catfish usually sets traps or basic fishing rods one. The global catch is over 10,000 tons per year, with the majority of the catches being made in the CIS countries .
    Sport fishing for catfish
    Here, the catfish are tracked with special, very strongly designed hand rods. A bait fish or a bundle of rope worms , which is attached to one or more hooks, is often used as bait . This bait can now be offered to the catfish via various assemblies such as bracing assembly, U-pose assembly or buoy assembly. The sport of fishing for catfish is becoming increasingly popular, not least due to the extreme power of the fish in the fight.

    Aquaculture

    European catfish have been bred in pond cultures , especially in Hungary , since the beginning of the 20th century . Since the late 1950s, the culture was introduced to other countries in Eastern and later also in Southeast and Central Europe. In addition to keeping in ponds, culture in nets within larger bodies of water and in modern recirculation systems is of increasing importance. Catfish can be reproduced semi-artificially or artificially in captivity. The semi-artificial reproduction takes place through targeted transfer in spawning waters with suitably prepared nests. For artificial reproduction, the animals are treated by injecting pituitary extract, after which the sex products can be obtained by stripping and artificially brought together.

    The volume of European catfish aquaculture was around 2000 tons outside Russia, of which Bulgaria accounted for a little over half . Above all, the problem is the relatively high costs in comparison to the catfish from the families of the shark catfish (Pangasiidae), catfish (Ictaluridae) and gill sac catfish (Clariidae) bred outside of Europe . In order to increase yields, attempts have been made to create single-sex herds, with males growing faster and having higher slaughter yields than females. Experiments with triploid animals resulted in reduced growth and lower survival rates.

    literature

    • Jozef Mihálik: The catfish. (= Die Neue Brehm-Bücherei. Volume 209). 2nd unchanged edition. Westarp Sciences, Magdeburg 1995, ISBN 3-89432-655-7 .
    • Gordon H. Copp, J. Robert Britton, Julien Cucherousset, Emili Garcıa-Berthou, Ruth Kirk, Edmund Peeler, Saulius Stakenas: Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges . In: Fish and Fisheries . tape 10 , 2009, p. 252–282 (English, full text [PDF; 522 kB ]).
    • Martin Hochleithner: Catfish (Siluridae) - biology and aquaculture . Aqua Tech Publications, Kitzbühel 2006, ISBN 3-9500968-7-6 , p. 71-74 .

    Documentation

    • Bertrand Loyer: Giant fish in our rivers . Arte (France), 2015, 44 min.

    Web links

    Commons : Wels  - album with pictures, videos and audio files
    Wiktionary: Wels  - explanations of meanings, word origins, synonyms, translations

    Individual evidence

    1. ↑ a b Regina Petz-Glechner: The names of our fish - an etymological search for traces - 18th catfish . In: Austria's fishery . tape 59 , no. 10 , 2006, p. 238–239 ( full text [PDF]).
    2. ↑ a b c d Midori Kobayakawa: Systematic Revision of the Catfish Genus Silurus, with Description of a New Species from Thailand and Burma . In: Japanese Journal of Ichthyology . tape 36 , no. 2 , 1989, pp. 155-186 (English).
    3. ↑ a b c d e f g h i j k l Jozef Mihálik: The catfish. (= Die Neue Brehm-Bücherei. Volume 209). 2nd unchanged edition. Westarp Sciences, Magdeburg 1995, ISBN 3-89432-655-7 .
    4. ↑ a b c d e Roland Gerstmeier, Thomas Romig: The freshwater fish of Europe for nature lovers and anglers . 2nd Edition. Franckh-Kosmos, Stuttgart 2003, ISBN 3-440-09483-9 , pp. 305-308 .
    5. ↑ a b c Günther Sterba : Freshwater fish of the world . 2nd Edition. Urania, Leipzig 1990, ISBN 3-332-00109-4 , p. 336, 353 .
    6. ↑ a b Uwe Hartmann: Freshwater fish . 2nd Edition. Ulmer, Stuttgart (Hohenheim) 2002, ISBN 3-8001-4296-1 , p. 140-141 .
    7. ↑ Vienna Drones: The white catfish. July 8, 2017. Retrieved July 12, 2017 .
    8. ↑ K. Kessler: On the ichthyology of southern Russia . In: Bulletin de la Société impériale des naturalistes de Moscou . tape 29 , 1856, pp. 350 .
    9. ↑ a b c d e Martin Hochleithner : Welse (Siluridae) - Biology and Aquaculture . Aqua Tech Publications, Kitzbühel 2006, ISBN 3-9500968-7-6 , p. 71-74 .
    10. ↑ a b c European catfish on Fishbase.org (English)
    11. ^ Fishing World Records
    12. ↑ Jürgen Volz: On the natural population of the catfish, Silurus glanis, in the Dutch Rhine delta . In: Fischökologie . tape 7 , 1994, pp. 61-70 .
    13. ↑ a b c d e f g h Gordon H. Copp, J. Robert Britton, Julien Cucherousset, Emili Garcıa-Berthou, Ruth Kirk, Edmund Peeler, Saulius Stakenas: Voracious invader or benign feline? A review of the environmental biology of European catfish Silurus glanis in its native and introduced ranges . In: Fish and Fisheries . tape 10 , 2009, p. 252–282 (English, full text [PDF; 522 kB ]).
    14. ↑ Silurus glanis in the endangered Red List species the IUCN 2008 Posted by: J. Freyhof, M. Kottelat, 2008. Accessed January 6 of 2009.
    15. ↑ A. Triantafyllidis, F. Krieg, C. Cottin, TJ Abatzopoulos, C. Triantaphyllidis, R. Guyomard: Genetic structure and phylogeography of European catfish (Silurus glanis) populations . In: Molecular Ecology . tape 11 , 2002, p. 1039-1055 (English, full text [PDF; 375 kB ]).
    16. ↑ Christoph Seidler: Puzzling swarm behavior - giant fish plague in the Rhône. Spiegel Online , October 6, 2011, accessed October 7, 2011 .
    17. ↑ Cucherousset, Bouletreau, Azemar, Compin, Guillaume and Santoul (2012): `` Freshwater Killer Whales '': Beaching Behavior of an Alien Fish to Hunt Land Birds. PLOS ONE doi: 10.1371 / journal.pone.0050840
    18. ↑ Catfish attack pigeons: fish catches birds. Spiegel Online, December 8, 2012, accessed on March 10, 2013 (video recordings).
    19. ↑ Conrad Gessner , Conrad Forer: From the Scheydfisch . In: Fischbuch . Cambier, Frankfurt am Main 1563, p. 378-380 ( digitized [accessed February 11, 2017]).
    20. ↑ Richard Eduard Ottmann: The Mosella of Decimus Magnus Ausonius . Verlag der Fr. Lintz'schen Buchdruckerei, Trier 1897 ( [1] [accessed on February 7, 2017]).
    21. ↑ Killer catfish: The legend of the killer fish in the online offer of the time
    22. ↑ Fish attack on girls - giant catfish grabs 14-year-olds in the swimming lake. Retrieved January 4, 2013 .
    23. ↑ a b Otomar Linhart, Ludek Stech, Jan Svarc, Marek Rodina, Jean Pear Audebert, Jean Grecu, Roland Billard: The culture of the European catfish, Silurus glanis, in the Czech Republic and in France . In: Aquatic living resources . tape 15 , 2002, p. 139–144 (English, full text [PDF]).
    24. ↑ fischlexikon.eu: European catfish
    This article was added to the list of excellent articles on November 11, 2009 in this version .