Talking fish: Wide variety of sounds discovered

By Charles Q. Choi

updated 2:18 p.m. ET Dec. 28, 2006

Increasingly scientists are discovering unusual mechanisms by which fish make and hear secret whispers, grunts and thumps to attract mates and ward off the enemy.

In just one bizarre instance, seahorses create clicks by tossing their heads. They snap the rear edge of their skulls against their star-shaped bony crests.

This and other discoveries made in recent years come as the focus on the sounds that fish make is growing beyond "really loud sounds that last a long time," fish behaviorist Timothy Tricas at the University of Hawaii at Manoa told LiveScience. "Seahorse clicks are brief, only about five to 20 milliseconds," he said.

There are more than 25,000 species of fish living today, more kinds than any other animal form with a backbone in the history of the planet. A lot of them appeared to have done well in school.

1,000 voices
"We know so far that at least 1,000 fish species make sounds, with a huge diversity of means by which they generate and listen to sounds," Tricas said. "There's only a handful we know well so far."

Tricas and his colleagues studied butterflyfishes, a family that includes 126 species with bright colors and striking patterns found on just about every coral reef in the world. One group within the butterflyfish family, comprising more than 80 species, are the only fish known so far to couple their swim bladders, which are organs that improve hearing, with their body's lateral lines, organs running down their sides that help detect motion in the surrounding water. This might be akin to a person hearing sounds by wiring their ears together with the little hairs on his or her skin.

This setup in butterflyfish seemed like a possible new hearing system, "but no one had ever heard butterflyfish make a sound. We discovered they do," Tricas said.

Using underwater cameras and sound recorders known as hydrophones on Hawaiian coral reefs, Tricas and his colleagues discovered butterflyfish emitted several types of sounds only 10 to 150 milliseconds long using tail slaps, fin flicks, fin spine extensions, grunts and jumps.

"If you're up close to them with a hydrophone, you can hear the sounds, but the total power in a single sound is miniscule compared to the loud and long sounds the toadfish and (fish known as) midshipman can make, which can last for seconds or minutes and can be heard 10 to 20 feet away," Tricas said.

Tricas presented research on these and other fish sounds at a meeting of the Acoustical Society of America in Hawaii last month.

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