Can Fish Hear Underwater?

If you̵7;ve ever tried to talk to someone while swimming in the pool, it may seem hard to believe anything could hear under water. Fish hear differently than humans, however, with specialized ears tuned for understanding sounds beneath the waves. By using their inner ear, swim bladder and lateral line system, fish are capable of hearing all the sounds in their environment.

  1. The Importance of Sound

    • Hearing is likely one of the earliest senses to have evolved. While we use sound for communicating, the first ears helped fish better understand their environment. Hearing allows a fish to get information from long distances, unlike vision or touch. Fish use sound when looking to find a suitable place to live by analyzing the ambient noises made by different environments. Fish also make noises for mating purposes or to scare off potential predators.

    Inner Ear

    • Fish bodies have a density almost identical to the water surrounding them, which means sound waves pass through them. Fish developed dense bones called otoliths that make up the inner ear. Tiny hairs called cilia are located inside the inner ear and move in response to sound waves. Sound moves at different speeds through the dense bones of the ear and the cilia. The fish̵7;s brain translates the difference of movement into sound.

    Swim Bladder

    • Most bony fish have an organ called a swim bladder. The swim bladder is a gas-filled organ that fish use to stay buoyant. Sound pressure waves can compress the gases in the swim bladder, which can aid a fish in hearing. In some species the swim bladder is connected to the inner ear via specialized bones. Fish with swim bladders connected to their inner ears have much sharper hearing than fish with a swim bladder that isn̵7;t connected, or that lack a swim bladder all together.

    Lateral Line Organ

    • Almost all fish have some kind of lateral line organ. The lateral line organ is a series of dense collections of tiny hair cells called neuromasts, located on or just beneath the surface of the skin and running the length of the body. The tiny hairs can move in response to sound waves and transmit acoustical information to the brain. Fish also use lateral line organs to respond to changes in water movement around them. This allows them to sense potential predators or for large schools of fish to swim in unison without bumping into one another.