Table size catfish – from 0.6g to 2kg. A freshwater or marine fish with whisker-like barbels round the mouth, typically bottom-dwelling.Catfish (or catfishes) are a diverse group of ray-finned fish. There are armour-plated types and there are also naked types, neither having scales. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species are important in the aquarium hobby.