Channel catfish live in water where sight is often useless. Their solution is external chemoreception: taste receptor cells distributed across the whole body surface, densest on the barbels and head but present down to the tail fin. Counts in the literature run to roughly 100,000 to 200,000 taste buds in an adult, far more than the several thousand a human carries on the tongue.
The sensitivity is extreme. Behavioural and electrophysiological work at Utah State University and elsewhere showed responses to amino acids at concentrations in the nanomolar range, which allows a catfish to locate a food source and swim up its chemical gradient without seeing it. Whiskers, or barbels, are best understood as one part of a body-wide sensor array rather than as the sole organ.
A persistent error is calling the barbels stinging or venomous. The barbels are soft and harmless; it is the pectoral and dorsal spines of some catfishes that carry venom glands.