But, they differ from humans in that they do not have openings to the body's surface. Instead, sound waves travel through the skin, flesh and bone of the fish's head to the otoliths. Hearing done in this manner is directional just like ours. Secondly, scientists have discovered a link between the swim bladder and their ears. Covered by an elastic membrane, the swim bladder vibrates like a drum head or a microphone to amplify even the faintest signals that reach it.
Fish also have lateral lines.
These are channels that begin on either side of their heads. These channels merge as a thicker horizontal line extending down each side of their bodies. They can be easily seen on some types of fish. The lateral lines purpose is to pick up close sounds and pinpoint their origin. Lateral lines are the ones that fish depend on most to detect noise created by nearby schools of baitfish or other tasty morsels, like a crayfish or worm.