Silurus glanis

Geographic Range

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.

• Biogeographic Regions
• palearctic palearctic
  • introduced introduced
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• brackish water brackish water

Physical Description

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

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.

Reproduction

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.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

The male protects the eggs until they hatch.

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • protecting
    • male

Lifespan/Longevity

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.

Behavior

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.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• solitary solitary

Home Range

Nothing is known about home range sizes or patterns of movement in these catfish.

Communication and Perception

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.

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore
• planktivore planktivore

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• carrion carrion
• insects
• mollusks
• terrestrial worms
• aquatic crustaceans
• zooplankton zooplankton

• Plant Foods
• phytoplankton phytoplankton

Predation

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.

Ecosystem Roles

Silurus glanis carry bacterial diseases that can be transmitted to other fish. They are important predators of fish, crustaceans, small mammals, and aquatic birds.

Economic Importance for Humans: Positive

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.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

Silurus glanis introductions have been implicated in declining populations of other commercial fishes.

Conservation Status

Siluris 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.

Other Comments

Common names for S. glanis are wels catfish or sheatfish.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

CARRIE SLONE (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.

References

ALP, A., C. KARA, H. BUYUKUAPAR. 2004. Reproductive Biology in a Native European Catfish, Silurus glanis. Turkey Journal of Veterinary Animal Science , 28: 613-622. Accessed December 07, 2005 at http://journals.tubitak.gov.tr/veterinary/issues/vet-04-28-3/vet-28-3-24-0303-29.pdf .

Black, A. Predator-fishing.co.uk 2005. "Siluridae" (On-line). Accessed October 31, 2005 at http://www.predator-fishing.co.uk/articles/essay.htm .

Bridgeman, G. Predator-fishing.co.uk 2005. "The 'Old World' catfish, Silurus.glanis; it's evolutionary success story and unrivalled feeding strategy" (On-line). Accessed October 31, 2005 at http://www.predator-fishing.co.uk/articles/outwiththeold.htm .

DOGAN BORA, N., A. GUL. 2004. Feeding Biology of Silurus glanis (L., 1758). Turkey Journal of Veterinary Animal Science , 28: 471-479. Accessed December 07, 2005 at http://journals.tubitak.gov.tr/veterinary/issues/vet-04-28-3/vet-28-3-3-0208-17.pdf .

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 .

Farkas, J. 1985. Filamentous Flavobacterium sp. isolated from fish with gill diseases in cold water. Aquaculture , Volume 44, Issue 1: 1-10. 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=21&_fmt=summary&_udi=B6T4D-49NPK1V-XH&_coverDate=01%2F15%2F1985&_cdi=4972&_orig=search&_st=13&_sort=d&view=c&_acct=C000043360&_version=1&_urlVersion=0&_userid=4159506&md5=d2cb75770e5fd2588d18061914f5a4c3 .

Froese, R., D. Pauly. 2005. "Silurus glanis" (On-line). Accessed October 31, 2005 at http://fishbase.org/Summary/speciesSummary.php?ID=289&genusname=Silurus&speciesname=glanis .

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 .