Silurus glanis Linnaeus,
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.
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
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
Bühler who helped to prepare this updated version ( Oct.
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.
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.
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.
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!
|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
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
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.
: Pertaining to the
upper jaw. (maxillary barbels)
Mandibular barbels : Pertaining to the
lower jaw. (mandibualr barbels)
Freshwater Fishes of Britain and Europe 1983
Grizmeck's Animal Life Encyclopedia Volume 4 Fishes
Sterba's Freshwater fishes of the World Vol.1
Internet discussion, Oct. 2008.