Clear water will give the fish a black color, while muddy water will often tend to produce green-brown specimens. With its sharp pectoral fins, it creates an eddy to disorient its victim, which the predator sucks into its mouth and swallows whole. The wels relies largely on hearing and smell for hunting prey (owing to its sensitive Weberian apparatus and chemoreceptors), although like many other catfish, the species exhibits a tapetum lucidum, providing its eyes with a degree of sensitivity at night, when the species is most active. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin relatively far forward. The wels catfish's mouth contains lines of numerous small teeth, two long barbels on the upper jaw and four shorter barbels on the lower jaw. Wels is a variation of Old High German wal, from Proto-Germanic *hwalaz – the same source as for whale – from Proto-Indo-European *(s)kʷálos ('sheatfish'). The English common name comes from Wels, the common name of the species in German language.

It has been introduced to Western Europe as a prized sport fish and is now found from the United Kingdom east to Kazakhstan and China and south to Greece and Turkey. The wels catfish ( / ˈ w ɛ l s/ or / ˈ v ɛ l s/ Silurus glanis), also called sheatfish or just wels, is a large species of catfish native to wide areas of central, southern, and eastern Europe, in the basins of the Baltic, Black and Caspian Seas.

Fishing planet unique blue catfish