It may be surprising to note that fishes can smell things just like other creatures. And like other animals they have noses for this purpose.
There are two pairs of nostrils in a fish. Each nostril has two openings which are called pits. One opening is in the front, and the other directly behind it. The two are separated by a small flap. However, the location of the nostrils may vary from species to species.
When a fish is under water, a current of water enters from the front pit and comes out through the rear one. As the water flows inside, it stimulates the sense cells which enable the fish to catch the smell. Many fishes have a keen sense of smell. They can detect even the faintest smells.
In fact, the sense of smell may be important to a fish in helping it find its way home. Some fish could distinguish between the water of two creeks through smell. But if their noses are plugged, they get lost. To prove this fact some researchers had performed certain experiments. In one experiment a large number of salmon fish were taken out of their home stream. Half of them had their noses plugged; the other half did not. The fishes with plugged noses got lost and the rest half could find their way back home again. Anglers use peculiar scented fish-food to attract them.
Apart from the sense of smell the fishes have other sensory perceptions also such as the sense of touch, taste, hearing and seeing.