By Andrew Black
Family:- Siluridae. Catfish:-
There are about a dozen members of this family which includes Silurus asotus from Japan,
Silurus berdmorei from India, Silurus gilberti From China, etc. but in Europe the main two
groups are Wels; Silurus glanis, and Aristotles Catfish; Silurus aristotels. The latter is
very similar to the Wels, but only possesses two barbules under the lower jaw, where the
Wels, has four. The Wels is easily recognized by its huge wide mouth, it has six whiskers,
two long ones on the upper jaw, and four smaller ones under its chin. They are also
characterised by their long anguilliform bodies, and their lack of obvious scales. They
have a one very small dorsal fin, and an elongated anal fin, which stretches for half of
the fishes body. They have a row of small "sand-paper" like teeth on both the
top and bottom jaws, each row consists of hundreds of teeth, these teeth are soft, and are
used to grip the prey, they slope inwards toward the back of the mouth. In front of the
throat cavity are two crushing plates, which the Wels uses to squash its prey prior to
swallowing. They also have a number of short spikes on the edge of the gill rakers, it
uses these to manipulate its pray prior to swallowing. Although this description might
sound horrible, it is quite safe to put your hand (and arm) into a catfishes mouth, the
teeth are soft, and only occasionally scratch in fact one way to carry the Wels is called
the "Waller grip", where the thumb is placed on the teeth and the fore finger is
placed under the cats jaw for grip.
Species: Silurus glanis;
The European Wels Catfish:
The Wels is naturally distributed all over Eastern Europe and Asia, with high
concentrations in the Danube and Volga basins. Through the intervention of man the Wels
has since found its way into many rivers and lakes in Germany, France, Spain, England and
Holland, (see Fig 1). Silurus glanis, Has many different names; in Holland it is known as "Meerval", in Russia "Ssum", Czechoslovakia "Sumec", Spain
"Siluro", Germany "Wels or Waller", and in France "Silure".
But In Britain it is known as "Catfish", a name which could apply to many
thousands of species world wide, and often causes confusion. The catfish is widely
distributed, but has a greater concentration in the counties of Bedfordshire,
Buckinghamshire, and Cambridgeshire. The Wels is not indigenous to this country, they
where first introduced into "Shoulder of Mutton Lake", at Woburn Abbey, in
Bedfordshire, on 27/10/1880. Since then they have been stocked both legally and illegally
into lots of lakes throughout the country .
In Russia "Ssum" are frequently caught at 600lb+, by trawlers. In Germany,
France, and Spain they are caught often at over 100 lb, and a 100lb cat is usually over 6
feet in length. Though in England the record catfish is only a baby at 57lb 4oz. Through a
study of bones, it is thought that maximum size for this species is around 1,000lb, such
specimens are thought to live in some of the big Russian lakes, where the commercial
trawling vessels can't fish, and the local anglers use baby pigs for bait. In freshwater
the catfish's size is only surpassed by the white sturgeon, Huso Huso, which may attain
weights of 2,200lb, but, sturgeon is not regarded as a freshwater fish as most of its life
is spent in the sea. Therefore Silurus glanis is the largest freshwater fish in the world.
It is especially suited to the slow-flowing reaches of the larger rivers, and lakes with
dense weed-beds, and muddy bottoms. But, Catfish are very adaptable and can even be found
in the strongest currents of the River Po in Italy, where fish up to 200 lb can be seen
feeding in "boiling" water, where the current is so strong that boats are unable
to anchor. Silurus glanis is mainly a nocturnal scavenger, and feeds best in warm weather,
and at night. In the UK they spend many days without feeding, and then gorge themselves.
On the continent, where the water is warmer, they feed more. Though mainly a scavenger,
feeding on mussels and crayfish etc., it will also feed on live fish, which it finds by
using its long whiskers to feel vibrations given off by injured fish.
Mainly dead or live fish. Though larger specimens will eat most things, frogs, rats,
coypu, snakes etc. In Russia several specimens have been found with human remains in their
guts, although it is thought that the individuals drown first - then are eaten whole.
There has never been a reported incident of catfish attacking divers, though they do
attack boats, but, this is thought to be a territorial response.
The male has a thin pointed flap of skin behind the vent. In the female this flap of skin
is shorter and fatter .
Spawning: In England spawning takes place from May to July, when the water temperature
is around 20.C. The eggs hatch after 3 days dependent on temperature. The larva, which are
about 7mm long and have one barbule, feed on plankton, later becoming more predatory and
feeding on small fish. The fish grow very rapidly and in ideal conditions reach 1lb in
weight in the first year. Catfish are also very easy to induce to spawn with the use of
hormones. With 5 mg/kg C.P.E or similar, applied to both sexes. In the less developed
countries, Wels are just simply left to spawn of their own accord, in primitive mud ponds
with just wool or rope added as a spawning material. The Male fish digs a scrape in the
bottom mud, and the female then deposits the eggs in a gelatinous lump within the
depression, the male then guards the eggs until they hatch.
In Europe, especially in the less developed countries, eg Poland, the Wels is an important
food fish, and its flesh is considered a delicacy. In Germany, France and Spain, the
catfish is of less regard, and the only commercial interest is for tourism (people travel
to fish the large rivers, and so stay in the hotels in the area). In England the fish are
widely sought after in the fishing fraternity, with demand greater then the fish
production, and consequently the fish sell for a very high price (GBP25 per lb for a
single figure fish, rising to GBP40 per lb for a 30lb fish). It is illegal to import
catfish into this country, except for the aquarium trade, or for use as brood fish.
Silurus glanis is important in the food industry of certain countries, and I think that
this could be true here. It is possible to rear them on a large scale, but, at present, it
is hard to get a licence to breed them, as they are not an indigenous fish, and the NRA
and NAFF are worried about fish getting into water courses. But, there is no evidence to
suggest that the Wels would be detrimental to the fish stocks in these rivers, and every
lake and river they have been stocked in, so far, have been superb fisheries. The Wels
should be regarded as a scavenger rather then an "active" predator. At present
there is a great demand for the species from a fishing point of view, because they are a
great sporting species, and prices can be high. It is illegal to import Wels at present,
to stop spread of disease, but I think that this will change soon, as the Wels is very
resilient to disease, and is not affected by certain diseases eg SVC, because it is not of
the same family as other more susceptible coarse fish. They are easy to breed and rear,
and have an incredible growth rate, with the fish reaching a marketable size within two
years at which stage they are about 4lb in weight. They will feed on scraps and dead fish,
and could be reared very cheaply. Such fast growth, and ease of keeping, make it an ideal
fish for the food market, and in a few years time we might be having Wels and chips,
instead of the more expensive alternatives.
N.B. the prices for catfish have dropped dramatically in the last few years, due Mainly
Whiskers, CCG, various.
Catfish, Kevin Maddocks.
A Report On Catfish, J. L. Fraser and Dr D. J. Shillcock.