There are at least 15 families of catfish around the world, both freshwater and sea, characterized by numerous barbules around the mouth and an absence of scales.

The largest is the wels or Danubian catfish (Siluris glanis), native to the rivers of central and eastern Europe. The wels is the only catfish found in British waters, having been introduced over 100 years ago. It still has limited distribution, confined mainly to lakes and pits in Bedfordshire and Buckingham¬shire, although it is spreading slowly to other parts.

The wels has a long, tapered body with a tiny, stunted tail and a huge, flattened head. The large, wide mouth has rubbery lips and many little teeth, with two long barbules on the upper lip and four smaller ones below the chin.

It feeds mainly on fish, but will eat almost anything, including frogs, rats and water birds. It usually feeds at night, but will occasionally go on a daylight feeding binge during hot or thundery weather. The British record is a little over 40 pounds, but in Europe 100 and 200 pound wels are quite common. In the large rivers of the USSR, such as the Dneiper, it can reach over 650 pounds and a length of 16 feet; such fish are probably around a hundred years old.

The largest North American catfish is the blue catfish (Ictalurus jurcatus), which can grow to over 100 pounds although 20 to 50 pounds is more typical. The blue catfish is silvery blue on the back, lightening down the sides to a silver or white belly. The tail is forked, and like all North American catfish the blue has two short barbules on the top of the snout, two large ones extending back from the jaw hinges and four more slender ones below the chin.

The fish thrives in large, clear, fast-flowing rivers, where it feeds on fish and crayfish, and is widely distributed through the midwest and south of the USA and in Mexico.

The channel catfish (Ictalurus punctatus) is reared commercially for its fine-tasting flesh, and also offers good sport for the angler. Found in large, clean lakes and rivers from the Great Lakes south to the Gulf of Mexico, the channel cat migrates to small streams to spawn. The younger fish have a relatively slender body, with a silvery blue or olive back, paler flanks and a silver-white belly, and varying numbers of black spots. Older fish are thicker in the body and much darker in color. The channel catfish can grow to 4 60 pounds, but most rod-caught u fish are less than 15 pounds.

The flathead catfish (Pylodictis olivaris) is a large, mottled brown fish with a noticeably flattened head, which lives in the larger rivers of the Mississippi Valley. It feeds mainly on fish, and although its maximum weight is about 100 pounds, most of those caught weigh only a few pounds.

The flathead catfish is popular for its tasty flesh, as is the little white catfish (Ictalurus calus) found in the coastal streams of the A eastern and southern USA, and in western waters where it has been widely introduced. It grows to about 3 pounds, and its color varies from a pale, silvery blue to a silvery beige or white, with a white belly.

The most important of the , American saltwater catfishes are the sea catfish (AriusJelis) and the gafltopsail catfish (Bagre marinus). These are found from Cape Cod to the Gulf of Mexico, and there are several closely-related species in Pacific waters. The sea catfish has a maximum weight of about 3 pounds, around half that of the gafltopsail.

The bullheads are a group of small freshwater catfish which grow to weights of 1 to 3 pounds and are often caught for the pan. The brown bullhead (Ictalurus nebulosus) is a sleek, mottled brown fish found from the Great Lakes south to Florida and west to Mexico, living in weedy lakes and slow-flowing streams.

The black bullhead (Ictalurus melas) is green to black on the back, with paler sides and a white or yellow belly. Originally found from North Dakota south to Texas, and from there north east to New York, it has been introduced to many other parts of the country, and to some European waters where it has often multiplied to almost plague proportions, especially in France.

The natural range of the yellow bullhead (Ictalurus natalis) is from North Dakota to New York and Florida. This mottled yellow m catfish prefers sluggish streams, ponds and lake shallows with ‘ muddy bottoms, and is often confused with the flat bullhead (Ictalurus platycephalus). This fish, which occurs in the south eastern states, is best distinguished from the yellow bullhead by its flattened head, and a dark patch on the lower part of the dorsal fin.