Fish have the ability to smell as well as taste. This ability is called chemoreception, or detecting environmental chemical stimuli through smell and taste.
Fish have extremely well-developed chemoreception, especially some species of eels and sharks. Fish have two nostrils on both sides of their heads but there is no connection between the nostrils and the throat.
The chemoreception organ in fish is called the olfactory rosette. The size of this organ is proportional to a fish's sense of smell. Salmon and sharks can detect levels of a chemical that are as low as one part per billion.
Fish also have taste buds all over their mouths as well as on their lips and tongue. Some fish, such as catfish and goatfish, have whiskers, called barbels, that have taste structures.