Silurus glanis, sheatfish or wels catfish, is native to eastern Europe and Asia. It has been introduced to several other areas including Germany, France, Spain, England, Greece, Turkey and the Netherlands. (Black, Predator-fishing.co.uk 2005)
Silurus glanis 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. (Froese and Pauly, 2005)
The elongated, scaleless body has a strong upper body and a laterally flattened tail. Silurus glanis varies in color. The upper side is usually a dark color and the flanks and belly are more pale. The fins are brownish. The body has a mottled appearance that is sometimes accompanied by brown spots. These catfish can grow to be quite large, perhaps as large as 3 meters long. A maximum reported weight was 220 kg. Most individuals reach sizes between 1.3 and 1.6 meters. Silurus glanis reach an average of 45 kg and has been considered one of the largest freshwater fish in its range.
Silurus glanis individuals have 1 dorsal spine and 4 to 5 dorsal soft rays, 1 anal spine and 90 to 94 anal soft rays, and a caudal fin with 17 rays. They have paired pectoral fins with 1 spine and 14 to 17 soft rays each. Their paired pelvic fins are positioned behind the dorsal fin with 1 spine each and 11 to 12 soft rays each.
There are several members in the family Siluridae. Silurus glanis is distinguished by its smaller dorsal fin, only two pairs of barbels, and the caudal fin being distinct from the anal fin.
Sex can be determined by the flap of skin behind the vent, in males it is thin and comes to a point, females have a thicker and shorter flap of skin. (Black, Predator-fishing.co.uk 2005; Froese and Pauly, 2005)
The larvae hatch in approximately 3 days, measuring around 7 mm, and begin feeding on plankton. These fish grow quickly and can reach between 1.5 and 4.5 kg in their first year. (ALP, et al., 2004; Black, Predator-fishing.co.uk 2005; )
There is little known about mating behavior in this species. Males create nests where females deposit their eggs. Males then guard the eggs until they hatch.
The male creates a shallow depression that will hold thousands of eggs laid by the female. The eggs are protected by the male until they hatch. Females can lay about 30,000 eggs per kilogram of body weight. Males grow faster and mature earlier than females. One study found that males matured at 78.82 cm at age 3 and females matured at 87.05 cm at age 4. (Black, Predator-fishing.co.uk 2005)
The male protects the eggs until they hatch. (Black, Predator-fishing.co.uk 2005)
The longest know lifespan in the wild is 80 years old for S. glanis. The expected lifespan in the wild is as high as 20 to 30 years old. (Black, Predator-fishing.co.uk 2005; Froese and Pauly, 2005)
Silurus glanis is a solitary species that prefers still waters, usually with a soft bottom like mud. They may live in river bed holes under overhangs of banks, or under other obstructions on river or lake beds such as sunken trees. These fish are most active at night and can tolerate brackish water. (Kirsten Pohlmann, et al., 2001)
Nothing is known about home range sizes or patterns of movement in these catfish.
Silurus glanis individuals 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. Silurus glanis individuals may use path analysis to track prey. One study found that S. glanis can track the three-dimensional swim path of a guppy and successfully attack it without the presence of light. Little is known about communication in these mainly solitary animals. (Bridgeman, Predator-fishing.co.uk 2005)
Silurus glanis fry feed on plankton during their first year of life. When they reach larger sizes they begin to eat worms, snails, crustaceans, aquatic insects, and small fish. At adult sizes they will also prey on ducks, voles, crayfish, fish, eels, frogs, rats, coypu, and snakes. They 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. Silurus glanis manipulate their prey prior to consumption by using several short spikes along the edge of the gill rakers. (Black, Predator-fishing.co.uk 2005)
Northern pike (Esox lucius) and humans are two predators of Silurus glanis. Their large size protects adults from many predators. Smaller fish may be protected somewhat by their dorsal spines. (Froese and Pauly, 2005)
Silurus glanis carry bacterial diseases that can be transmitted to other fish. They are important predators of fish, crustaceans, small mammals, and aquatic birds. (Farkas and Szitóné, 1986; Farkas, 1985)
Silurus glanis is a commercial fish consumed by humans. This fish has boneless white flesh that is low in fat and highly palatable. Technological research for artificial reproduction, population genetics and conservation problems have been developed over the past 10 years in the Czech Republic, France and other European countries. It is also a valued game fish in European countries. (Froese and Pauly, 2005; Linhart, et al., 2002)
Silurus glanis introductions have been implicated in declining populations of other commercial fishes. (Froese and Pauly, 2005)
Silurus glanis populations appear to be stable. They are protected by Appendix III of the Bern Convention. In areas where these fish have been introduced, negative ecological consequences have been noted. (Froese and Pauly, 2005)
Common names for S. glanis are wels catfish or sheatfish. (Linhart, et al., 2002)
Tanya Dewey (editor), Animal Diversity Web.
CARRIE SLONE (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
an animal that mainly eats fish
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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Farkas, J., M. Szitóné. 1986. Vibrio disease of sheatfish (Silurus glanis L.) fry. Aquaculture, Volume 51, Issue 2: 81-88. Accessed November 01, 2005 at http://www.sciencedirect.com/science?_ob=ArticleURL&_aset=V-WA-A-W-WC-MsSAYZA-UUA-U-AABBVCECUZ-AABAUVUBUZ-VVVVYWDYC-WC-U&_rdoc=20&_fmt=summary&_udi=B6T4D-49NXD4X-1SC&_coverDate=01%2F01%2F1986&_cdi=4972&_orig=search&_st=13&_sort=d&view=c&_acct=C000043360&_version=1&_urlVersion=0&_userid=4159506&md5=1be4cd970b7851ee99258854225eb8d9.
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Kirsten Pohlmann, , Frank W. Grasso, Thomas Breithaupt. 2001. Tracking wakes: The nocturnal predatory strategy of piscivorous catfish. Proceedings of the National Academy of Sciences of the United States of America, June 19; 98(13): 7371–7374. Accessed October 31, 2005 at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=34675.
Linhart, O., L. Stech, J. Svarc, M. Rodina, J. Audebert, J. Grecu, R. Billard. 2002. The culture of the European catfish, Silurus glanis, in the Czech. Aquatic Living Resources, 15: 139-144. Accessed December 08, 2005 at http://www.edpsciences.org/articles/alr/pdf/2002/02/alr2099.pdf?access=ok.