Physiology

Physical Description

The Wels Catfish, Silurus Glanis, is an easily identified fish throughout its distributed range. It is characterised by having a long, scaleless anguiliform body. The Wels has a flattened head with a huge mouth and 6 barbules or whiskers. It has 2 long whiskers protruding from the upper jaw and 4 shorter barbules hanging from below the lower jaw. The Wels has a very small dorsal fin, almost a stump, and a very long anal fin that stretches over half the length of the body.

Although the Wels Catfish is an accomplished predator, it does not have rows of pronounced teeth such as a pike. Instead the Wels has pads in its upper and lower palate which consist of hundreds of tiny velcro-like teeth. It uses these pads to grip its prey which it then passes back to 4 crushing pads, 2 top and 2 bottom, at the back of its throat.

Colouration can vary considerably with Wels Catfish. They generally have a darker back with mottled sides and a paler underside. In clear water environments they can often appear as almost black on top and very dark mottled grey down the flanks. This dark top colour ranges from black, through brown and into shades of green. The flanks can vary from a dark grey or brown right through to orange or pale yellow. The underside is usually a very pale yellow, cream or white. There are two highly sought after colour variations of the Wels Catfish. The first is the ‘Mandarin’ catfish, this fish has far less mottling than normal and has an overall orange or yellow appearance. The second variation is the even rarer Albino catfish. This fish has a pinky white tinge to its body and come with the pink/red eyes that characterise albinism. A true albino Wels Catfish is a very rare fish. Both the albino and mandarin are highly sought after ‘trophy’ fish for those that fish for Wels.

Sexing the Wels Catfish

There are two visual ways to identify the sex of a Wels Catfish. The first is to look at the flap of skin behind the fishes vent. In the male Wels the skin flap is quite thin and is fairly pointed at the end. The vent flap of the female Wels is much thicker and is rounded at the end.

The other visual way to distinguish the sexes is to look at the leading ray of the fishes pectoral fins. A mature male has a thickened, rough pectoral fin with a very pronounced leading ray. The ray thickens and roughens to such an extent that it resembles a spike. This is not present in the female fish and the fin has a far softer appearance. This thickening of the male Wels pectoral fins becomes far more pronounced in the Spring prior to spawning.

Size and Growth Rates

There has been a lot of discussion as to the potential maximum size of the Wels Catfish. Whilst it is feasible that Wels could reach weights of 350lb in perfect conditions, .i.e. a warm climate and an abundance of prey, it is unlikely that it could grow to much bigger than this. Stories of 800lb monsters, usually from Russia, are either exaggerations or misidentified Beluga Sturgeon. The max length a Wels catfish could obtain would be around 3m in length. Growth rates in ideal conditions could be as high as 15lb per year.

Diet

The Wels Catfish can be described as a predatory scavenger. Its natural diet will consist of fish, amphibians, worms, waterfowl and small mammals such as water voles or rate. Basically the Wels catfish will eat anything, live or dead, that it can fit into its very large mouth.