Wels catfish
From Wikipedia, the free encyclopedia
 |
||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 |
||||||||||||||
|
|
||||||||||||||
| Scientific classification | ||||||||||||||
|
||||||||||||||
|
|
||||||||||||||
| Silurus glanis Linnaeus, 1758 |
The wels catfish, Silurus glanis, is a scaleless fresh-water catfish recognizable by its broad, flat head and wide mouth. The mouth contains lines of numerous small teeth, two long barbels on the upper jaw and four shorter barbels on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin positioned relatively far forward. It uses its sharp pectoral fins to capture prey: with these fins, it creates an eddy to disorient its victim, which it then simply engulfs in its enormous throat. It has very slippery green-brown skin. Its belly is pale yellow or white. Wels catfish live at least thirty years and have very good hearing.
The female produces up to 30,000 eggs per kilogram of body weight. The male guards the nest until the brood hatches, which, depending on water temperature, can last from three to ten days. If the water level decreases too much or too fast the male has been observed to splash the eggs with the muscular tail in order to keep them wet.
The wels catfish lives on annelid worms, gastropods, insects, crustaceans, and fish; the larger ones also eat frogs, mice, rats and aquatic birds like ducks.
Contents |
[edit] Habitat
The wels catfish lives in large, warm lakes and deep, slow-flowing rivers. It prefers to remain sheltered in places such as holes in the riverbed, sunken trees, etc. It consumes its food in the open water or on the bottom, where it can be recognized by its superior mouth. Wels catfish are food fish and are also kept in fish ponds. However, only the meat of younger animals is palatable.
The wels catfish is found in wide areas of central, southern, and eastern Europe, and near the Baltic and Caspian Seas.
[edit] Physical characteristics
Colour varies with environement : clear water will produce black while muddy water will often turn to brownish. Weight and length are not correlated linearly, and also depends on the season.
With a possible total length up to three m (ten feet) and a maximum weight of over 150 kg (330 lbs) it is the second largest freshwater fish in its region after the sturgeon. However, such extreme lengths are extremely rare and could not be proved during the last century, but there is a somewhat credible report from the 19th century of a wels catfish of this size.
Most wels catfish are only about 1.3 to 1.6 m (4 ft 3 in to 5 ft 3 in) long; fish longer than 2 m (6 ft 6 in) are normally extremely rare. At 1.5 m they can weigh 15 to 20 kg and at 2.20 m they can weigh 65 kg.
Only under exceptionally good living circumstances can the wels catfish reach lengths of more than two m, as with the record wels catfish of Kiebingen (near Rottenburg, Germany), which was 2.49 m (8 ft 2 in) long and weighed 89 kg (196 lb). This giant was surpassed by some even larger specimens from France, Spain (in the River Ebro), Italy (in the River Po), and Greece, where this fish was released a few decades ago. It grows very well at that location thanks to the mild climate, lack of competition, and good food supply. The record sized was 3 m (9.9 ft) long fish, caught in the Danube in Romania, weighing about 220 kg (440 lb), until only recently when a 226lb (102kg), 8ft (2.4m)monster was caught in the Ebro River in Spain by Carl Smith.[1]. Other reports of larger wels are unlikely and are often regarded as typical big fish stories or in some cases misidentifications of the now rare sturgeon.
[edit] Ecology
There are concerns about the ecological impact of introducing the wels catfish to non-native regions. These concerns take into account the situation in Lake Victoria in Africa, where Nile perch (available in stores as Lake Victoria perch) were introduced and rapidly caused the extinction of numerous indigenous species. This severely impacted the entire lake, destroying much of the original ecosystem. The danger does not appear to be as extreme in the case of the wels catfish, but the introduction of foreign species is almost always a burden on the affected ecosystem.
[edit] As Food Fish
Meat of Silurus glanis is regarded as good to eat when the catfish has a weight under 15 kg. Larger than this size, the fish is very fat and not recommended for consumption, unless it is caught in April, after the winter. It should be noted that the eggs are poisonous and should not be consumed.
[edit] Fishing
For fishing techniques, one of the best baits are the bloodsuckers, turned inside-out on the hooks and one bait that nearly never fails and is guaranteed to attract one catfish is the fresh water eel. Attached carefully to the hook, not to break the spine, it will remain alive for a long period of time while emitting sounds that attract the catfish. Other common baits are different types of dead and living baitfish, clumps of large earthworms and sometimes also innards or pieces of squid. During the winter is fished with a special trawler that sweeps the river bed. Once caught, the fish is very slippery and difficult to master in the boat, once it begins to wrestle there. The tail must be avoided carefully, because it is quite powerful. But there is one way of calming it down : press the barbels between fingers and as they are hypersensitive the fish will paralyze under the pain. While some specimens clearly reach lengths over 2.50 m, there are no recorded attacks on humans.
[edit] Related species
- Aristotle catfish (Silurus aristotelis) from Greece, the only other native European catfish species beside Silurus glanis.
- Amur catfish (Silurus asotus), introduced to European rivers
- Brown bullhead (Ameiurus nebulosus)
- Giant Mekong catfish on the lower reaches of the Mekong
[edit] References
- World Conservation Monitoring Centre (1996). Silurus glanis. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 09 May 2006.
- "Silurus glanis". FishBase. Ed. Ranier Froese and Daniel Pauly. March 2006 version. N.p.: FishBase, 2006.
- Silurus glanis (TSN 164068). Integrated Taxonomic Information System. Accessed on 19 March 2006.
[edit] External links
- This article includes information translated out of the German and French Wikipedias.
