Fish Stories

There are more than 25,000 species of living fishes. That's more different kinds of fish than any other animal with a spine in the whole history of our planet. Today, we know of more than 1,000 species that make sounds. Scientists who study fish noises have discovered many things over the past 20 years about how and why they make sounds.

How do seahorses make noise? Not through their mouths and voiceboxes and breaths like people. Seahorses actually have bones in their heads that click!

Over 100 years ago, scientists noticed that seahorses make a clicking sound. At first they thought that when the seahorse lifted its head, it made small gas bubbles explode. But using new video techniques, scientists noticed that a sound came out as the top of the seahorses' heads moved in a funny way that rubbed two bones near the top of the seahorse's head and "mane." The bones would pop up and down to make the sound, much like snapping two tiddlywinks together. This way, the sea horse could click to mates, strangers, and also during feeding.

A lot of fish have an air pocket inside their bodies known as a "swim bladder." Minnows, eels, anchovies and goldfish all have swim bladders that they use to keep themselves from sinking in the water. Some kinds of fish use this bladder for more than just staying in place. Some fishes make muscles in their bladders move back and forth very quickly, twitching in the same way the muscles in your jaw twitch when your teeth chatter.

However, scientists have recently discovered one fish has a swim bladder to make sound, but it doesn’t have fast, jittery muscles controlling it. The pearlfish has a much slower muscle in its swim bladder, and it uses the bladder to make sound. The pearlfish doesn’t live like other fish, swimming around in the ocean or lake. It lives inside a live starfish or a tube-shaped animal called a sea cucumber. So, how do these fish talk to each other from inside their houses? That slow muscle inside the swim bladder pulls back, then it releases the front of the swim bladder like a snapped rubber band against a drum. This makes a very strong, low sound that the other pearlfish can hear, even if they are outside the starfish.

One particular fish scientist, Art Myrberg Jr., spent his whole life thinking about questions like these. Fish sound scientists gathered together last month at a scientific meeting to hear about some things Myrberg discovered about fish noises. Here are some things Myrberg found out about noisy fish.

Fish make sounds for different reasons. They may try to find food, look for mates, or see who's a stranger and who's a friend, using sound. Myrberg studied several species of fish called damselfish. That sounds like it might be a sweet young fish who'd take you home for a cup of tea, but really the damselfish is aggressive, yelling at and chasing strangers.

A male damselfish can chirp and make lots of other sounds. He chirps when he is trying to attract a female to his nest, and he makes chirps and pops when warning strangers away from his area. The damselfish listens for the time between noises to find out if the noise comes from the same or another kind of damselfish. If that other fish is a damselfish, but not a friend, the damselfish gets aggressive and makes a "keep out!" sound. It's a code of communication between damselfish, like talking in humans.

Contact:

Timothy Tricas
University of Hawaii at Manoa
Tel: 808-956-8677
tricas@hawaii.edu

Martha Heil
American Institute of Physics
Tel: 301-209-3088
mheil@aip.org