National Aquarium | A Blue View: Fish That Make Sound

The goal of these calling cards is often to woo potential mates or frighten off predators. Sometime’s it’s simply a sign of distress of a byproduct of motion!

Unlike the vocal chords utilized by many terrestrial species, these coniferous fish have other means of producing sound—drumming, stridulation and hydrodynamics. And the sounds almost always occur at low frequencies.

Drumming

Did you know? Most fish have a swim bladder—a pocket of air in the abdomen that helps control buoyancy. Some fish also have what’s called a sonic muscle attached to, or near, the swim bladder. When the sonic muscle contracts, it causes the swim bladder to rapidly inflate and delate, creating sound.

The sound emanating from a vibrating swim bladder typically resembles the beating of a drum, but variations exist that can sound more like humming, growling or grunting. In the male toadfish, for instance, the vibration is reminiscent of a foghorn.

Stridulation

Some fish press their bones or teeth together to make noise—the process is called stridulation.

Sometimes, the stridulation is purposeful. The channel catfish, for example, will rub its fins together to produce sound. In some instances, stridulation is simply the byproduct of a noisy eater—some seahorses have been known to make clicking sounds while feeding!

Hydrodynamics

The low-frequency sound produced when a fish rapidly changes its speed or direction is called hydrodynamic sound. Scientists believe hydrodynamic sound could have important implications in predator/prey dynamics—a noisy swimmer may inadvertently attract predators.

When you think of an animal that purrs, grunts, croaks or hums, I’ll bet it’s not a fish. But, I’ll let you in on a secret: More than 150 species of fish on the East Coast of the U.S. are what scientists call “somniferous.” They make noise. Lots of it.

Forget those dreamy underwater documentaries where all is peace and quiet. The ocean is like New York City at rush hour. There are thousands of species, and many have something to say. The tiny cusk eel sounds like a jackhammer. Damselfish purr. Long-horned sculpins hum like an iPhone set on “buzz.”

But, you may ask, how do fishes make sound? And this is where it gets very interesting. Lacking vocal chords, many of these somniferous sea creatures have a swim bladder muscle that vibrates an air-filled sac deep inside their bodies. Think of it as an anatomical drum. Others use stridulation, rubbing one body part against another, like a cricket’s chirp. Still other fish grind their teeth or flick their tail spines.

Among the many fish that use sound to communicate are ones most frequently caught to make fish and chips: the haddock and the famous Atlantic cod, which can “grow as big as a heavyweight boxer.” Cods grunt. Haddock sound like the revving of a motorcycle.

The black drum fish that have taken up residence in Florida's canal system make low-frequency booming noises that can carry through sea walls and into homes, becoming as much of a nuisance as loud neighbors. These fish can make a racket.

Our own Chesapeake oyster toadfish makes a distinctive foghorn sound when trying to attract a mate.

Perhaps the strangest sound of all—and one that kept the community of West Seattle on edge and awake at night in the fall of 2012—is the growl of the Midshipman fish. It has a low throbbing rumble, like the soundtrack of “Star Trek” when Spock and the gang were about to land on an unfriendly planet. It sounds otherworldly, eerie and ominous.

No wonder people couldn't sleep. But there was humor—not to mention peace of mind—in the explanatory headline, “Fish Mating Call Blamed for Loud Humming Sound in West Seattle.”

The scientists who study bioacoustics, the science of animal sound, know that fish—like other animals—make noises for a variety of reasons. They vocalize to attract mates, defend territory and warn of predators. They chorus to stay schooled together.

The sheer magnitude of this aquatic soundscape can sometimes be baffling. In the 1980s, near the end of the Cold War, the Swedish Navy was led to believe that the sound recordings they were collecting were evidence of hostile Russian submarines in their territorial waters. In fact, they were herring.

Not only can diplomatic crises be averted by listening carefully to fish sounds, but scientists are also using it to make acoustic maps to better understand the population distributions of fish, and to give fishermen advice on areas to avoid during mating seasons. This will help limit overfishing and give species like cod a chance to make a comeback.

The fish are talking. We're finally listening to what they have to say.

To learn more about the biology of fish sound—and to hear a cod grunt and a Midshipman fish growl—visit aqua.org/ablueview. This is John Racanelli of the National Aquarium for WYPR, your NPR news station.