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Silurus glanis  Linnaeus, 1758


his 'beasty' can grow, in exceptional circumstances, to just under 3 metres in the wild and is definitely not an aquarium fish unless kept in an indoor pool!, but the true reality is that most catches of this predator are more akin to the 1-1.5metres mark and weights of around 150kg (330lbs). There is actually 12 known species the world over, and glanis is the type-species. The name Silurus was used for some time for all naked catfishes until Bleeker identified the distinguishing characters of the various currently recognised groups. Silurus glanis was actually the first catfish to be scientifically recorded and it is synonymous to ScotCat as it is the first factsheet we have produced.


Silurus glanis


This is Europe's largest freshwater fish and is only one of two catfish indigenous to Europe the other from the same genus, Silurus aristotelis from the River Akelhoos in Greece. This species looks like the other wels, but its dorsal fin is smaller, and it has just two pairs of barbels. The caudal fin is distinct from the anal fin. In the east, there are some others, even Japan has a native species.

The Common name for glanis is the 'Wels Catfish' and is found in the Rhine River in Germany eastwards to the Black and Caspian Seas. It inhabits not only the Rhine in Germany, but more or less the whole country. It is naturally distributed in the whole of central Europe, eastern Europe and the southern part of central Asia as far west as France and as far east as larger parts of Russia in the north and as far south as Turkey and even a bit of Iran and Iraq. It is also native to some regions of southern Norway and Sweden. They were also introduced to some parts of Italy, mainly the Po delta where they became extremely common and the record catch of 2.78metres and a weight of 144kg. (316.8lbs) actually came from here. They also now live in the River Ebro in spain and some other waters of this country. Furthermore they were introduced to some lakes in Greece, as well as some lakes in England during the latter part of last century where clubs have been formed, relating only to these fish, with videos being produced of them being caught for sport in England, and other parts of Europe.

 

The diet in its natural habitat consists mainly of fish, especially species which are more common on the ground, but sometimes it also hunts near the surface. It eats also amphibians, small swimming mammals like mice, rats or voles (a normal dog is much too small, there are stories of dog-eating wels, but it was only a small dachshund puppy which is not bigger than a vole, so this is actually not that spectacular), dependent on its size a wide range of water birds from small hatchlings up to adult ducks. It consumes also comparably much invertebrates like crayfish, insects and their larvae, worms and leeches.

The elongated Wels body consists of a powerful forebody and a laterally greatly compressed tail shaft; the prominent anal fin merges with the caudal fin. This fish, with its calm undulating tail movements normally has its long pair of upper jaw barbels pointing straight forward, while the four smaller barbels of the lower lip hang down. The dorsal fin, consisting of just four rays, seems small for such a powerful animal.

What intrigues me most about this fish is the small size of the dorsal (which is common in the Siluridae family) compared to the size of the body and the long anal fin. Identification of the Silurus genus relates to the long anal fin, small dorsal fin with four or five rays without a spine, and minus an adipose fin. The caudal fin is usually round to emarginate.


A friend of mine actually went of to Spain to fish for them in a Lake flowing from the Ebro River where they were seemingly introduced by a German ichthyologist, and he had a rare old time!. Altogether I think, a very interesting animal.

 

Acknowledgement: Markus Bühler who helped to prepare this updated version ( Oct. 2008).


Characteristics
Dorsal 1/4; Anal 90-92; Pectorals; 1/14-17. Body elongate, cylindrical anteriorly, compressed posteriorly. Head large and depressed. Gape very wide. 3 pairs of barbels; the maxillary pair are especially long and when laid back, reach to beyond the pectorals. The dorsal fin is very small and inserted well forward. Adipose fin absent. Anal fin-base very long.

Colour
Colouration extremely variable; usually fairly dark, the upperside dark olive-green to blue-black and the flanks paler, occasionally with a red-brownish sheen. Underside, especially the belly, pale. Upon this ground colour are imposed cloudy or spotted marblings. Entirely black-blue and quite pale individuals also occur. Fins dark, red-brownish to brown-violet. Completely white, bright yellow or orange specimens are comparably common, which is very unusual for a big predatory fish. To describe the normal colour is problematic, because it varies a lot, but greyish marmorated is also a very common colour.

Compatibility
You can of course keep small Wels Catfish in an aquarium where feeding is no problem with dim lighting and a large external filter and they will eat anything ( just keep an eye on your household ‘cat’), but where would it go after outgrowing your tank as Public Aquariums have probably their full quota. As they are very predatory, you should never keep it together with smaller fish, because especially the small ones can swallow very big things. You should also get it some kind of shelter like a root or some kind of tube.

Sexing
Females are larger in the ventral area in the breeding season. If you compare older females and males of the same age, the males are typically a bit longer and more slender, but the females have a thicker body.

Breeding
In their native habitat in the spring (May-July), the eggs are laid in a shallow depression excavated by the male, the eggs can total into the thousands and the growth is very rapid, with them becoming sexually mature at between 4 and 5 years old and living up to 20 or 30 years. There are even reputed reports of them living to 80 years!

Feeding
You can actually keep a Wels in an aquarium as long as it is small enough, but you should NOT give it normal catfish food which contains a lot of plant-material. S. glanis is a highly carnivorous predator and will eat a lot of things. Worms are very good, as well as, dependent on its size, insect larvae. Crushed snails also work, but if they get bigger you should mainly feed them with fish. They will even eat dead fish or chunks of it, and I have often read that they even eat normal meat and squid in aquariums, but over a longer time this is possibly not that good.

Etymology
Silurus: From 'silouros', a kind of river fish. Silurus, sheetfish, catfish. According to Lacepéde (1803) this word indicates the rapidity with which Silurus can move its tail.
glanis: The name of a kind of fish.


Glossary of Terms:
Maxillary barbels : Pertaining to the upper jaw. (maxillary barbels)
Mandibular barbels : Pertaining to the lower jaw. (mandibualr barbels)


Reference
Wheeler, Alwyne Freshwater Fishes of Britain and Europe 1983
Grizmeck's Animal Life Encyclopedia Volume 4 Fishes 1, 1963
Sterba's Freshwater fishes of the World Vol.1 1973

Bühler, Markus: Internet discussion, Oct. 2008.

Photo Credits
Hans Reinhard  
  
Factsheet 001

Synonyms:
Siluris glanis, Silurus silurus, Silurus glanis aralensis    
Common Name:
Wels Cat
Family:
Siluridae
Subfamily:
Silurinae
Distribution:
Europe and Asia: Russia, Central & Eastern Europe. Germany, upper Rhine and eastwards to the Black and Caspian Seas.
Size: 
2.3m. (9ft)
Temp:
04-20°C (35-67°F)    
pH.:
6.0-8.0.
Hardness:
up to 30dGH
Donation:
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                                                                                                                                                  Factsheet 001= updated February 11, 2016 , © ScotCat 1997-2016 Go to Top