Wels catfish
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Order: Siluriformes
Family: Siluridae
[Photo] Wels Catfish (Silurus glanis); Silurus glanis Een 124 cm lange meerval gevangen door Lucas van der Geest. Foto geschonken door Lucas van der Geest. Source: http://nl.wikipedia.org/wiki/Afbeelding:EuropeseMeervalLucasVanDerGeest.jpg
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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 can live for 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 take 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 such as ducks.
Habitat
The wels catfish lives in large, warm lakes and deep, slow-flowing rivers. It prefers to remain in sheltered locations 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 large 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.
Physical characteristics
Colour varies with environment : clear water will give the fish a black coloration while muddy water will often tend to produce brownish specimens. Weight and length are not correlated linearly, and also depends on the season.
With a possible total length up to 3 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 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 2 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 Poland, 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 226 lb (102 kg), 8 ft (2.4 m) monster was caught in the Ebro River in Spain by Carl Smith. Other reports of larger wels(around 16 feet or more) are unlikely and are often regarded as typical big fish stories or in some cases misidentifications of the now rare sturgeon.
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.
As a food fish
The meat of Silurus glanis is regarded as good to eat when the catfish weighs less than 15 kg (33 lbs). Larger than this size, the fish is highly fatty and not recommended for consumption. The eggs are poisonous and should not be consumed.
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 powerful and difficult to master in the boat. Once there, is a quiet, no dangerous fish. While some specimens clearly reach lengths over 2.50 m, there are no recorded attacks on humans.
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
http://en.wikipedia.org/wiki/Wels_catfish
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