Wels Catfish

The wels catfish is among the giants of the freshwater world.

Despite their size, this massive behemoth is otherwise just like most catfish. They prowl around the bottom of freshwater rivers and lakes in search of food to eat. Popular in both commercial and recreational fishing, they are sometimes caught by people for the taste of their meat.

4 Wels Catfish Facts

• The common names wels appears to come from old Germanic. It can be traced back even farther to an ancient European word meaning sheatfish (the alternative name for this type of catfish).
• The wels catfish is thought be exceptionally sensitive to chemical signals in the water. It also has the ability to detect fine movements of water from nearby prey.
• The wels catfish lives in the cooling ponds of the Chernobyl Nuclear Power Plant. While these fish grow larger than anywhere else, it’s not because they’re mutated from the Chernobyl radiation. It’s because they are allowed to fully grow without being disturbed by humans. Despite the radiation, the Chernobyl populations appear to be healthy and thriving.
• Rare attacks on humans have been reported, but no one has lost their life from this species.

Classification and Scientific Name

The scientific name of the wels catfish is Silurus glanis. This name is thought to derive from an ancient Greek word meaning a large river fish. Wels catfish belongs to a genus that also includes other very large species, including the Amur catfish and Aristotle’s catfish.

Evolution

Owing to its status as one of the catfish species native to Asia and Europe, the Wels catfish belongs to the genus Silurus and the family Siluridae.

As a member of the Siluriformes, it shares the same heavy bony head, facial tendrils, and bare skin its closest relatives, other catfish are known for. A glimpse at the superorder it belongs to, the Ostariophysi reveals that it is also related to the following:

• Characiformes: Consisting of about 2,168 species, this order is the third largest of the superorder and includes piranhas and tetras.
• Cypriniformes: This order consists of 4,501 species and is the only group which contains more species than Siluriformes (which contain over 3,800 species). Examples include carp, loaches, and minnows.
• Gymnotiformes: The smallest member of the superorder, it contains about 240 species and occasionally gets lumped in with Siluriformes. Examples include banded, black ghost, and glass knifefish, and electric eels. 

The earliest members of the superorder are believed to have appeared on the evolutionary scene during the Jurassic about (145 – 200 million years ago). These early Ostariophysians were themselves the descendants of a single ancestor which first took to freshwater during the Triassic (251 million years ago).

Appearance

The most prominent characteristic of the Wels catfish is its enormous size. This giant of the river can reach up to 10 feet long and weigh a record 500 pounds. This would make it the second largest freshwater fish in all of Europe behind the beluga sturgeon. But most full-grown specimens are more like 4 to 6 feet long and weigh 200 pounds.

The Wels catfish is characterized by an extremely long, scale-less body with a flat tail, wide mouth, an exceptionally long anal fin running along the stomach, and a kind of mottled gray or greenish-brown skin (albino specimens have been reported as well). They have two long barbels (or “whiskers”) on the upper jaw and four shorter barbels on the lower jaw; these help the fish find their way in the water and search for food items in the sand.

Distribution, Population, and Habitat

The Wels catfish is native to the freshwater rivers and lakes of Europe and Asia. This species was introduced into Western Europe as a sport fish and even as far east as China. It is also found near coastal waters of the Baltic, Black, and Caspian Seas. According to the IUCN Red List, they are considered to be a species of least concern. However, this masks wide regional differences in population numbers. In some areas, it appears to be threatened by overfishing and habitat changes. Low genetic diversity is also contributing to the problem. Unfortunately, accurate population numbers are not available.

Predators and Prey

This fish sits near the top of the food chain. It feeds on a wide variety of different animals and in turn has few predators. Like many catfish, it sifts along the bottom of the water or ambushes prey in a sudden strike.

What eats the wels catfish?

Due to their enormous size, full-grown Wels catfish have few natural predators in the wild. Humans are about the only species which hunt them. Northern pike will eat juveniles as well.

What does the Wels catfish eat?

A full-grown wels catfish will consume snails, worms, crustaceans, aquatic insects, and smaller fish. They are even known to consume ducks, crayfish, frogs, rats, and snakes as well, even leaping out of the water to consume an unsuspecting animal. The suction force of their mouths helps them capture prey in the water. Young catfish fry, by contrast, mostly feed on plankton during the first year of life.

Reproduction and Lifespan

Unfortunately, there is a lot we still don’t understand about the reproduction and courtship behavior of the wels catfish. The spawning season seems to take place between May and July of each year. Like many other types of catfish, the male will create a nest in the sand where the female will lay its eggs. It’s estimated that the female can lay some 30,000 eggs per kilogram (2.2 pounds) of body weight. The male will then release its sperm into the water for the purpose of fertilizing them. During the three to 10-day gestation period, the male will stand guard over the eggs.

After hatching, the fry will feed on plankton and grow quickly. They can easily reach up to 10 pounds in the first year alone. The male will reach sexual maturity in about three years, whereas the female can take four years instead. The record lifespan in the wild is known to be 80 years, but 20 to 30 years is a more typical age of death due partly to diseases and hunting.

Fishing and Cooking

The wels catfish is valued in some circles as an important game fish for expert hunters who have the proper equipment to reel in this behemoth. The boneless white meat is low in fat and largely considered to be a delicacy.

1. , Available here: https://animaldiversity.org/accounts/Silurus_glanis/
2. (1970) https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=3651&Potential=Y&Type=2 Jump to top