Homing Beacon

March 1, 2008
By Damond Benningfield

A coral reef is not only busy and colorful, it’s noisy. Fish make popping and grunting sounds, and the clicks of hundreds of shrimp can sound like frying bacon. To newborn fish living far away from the reef, these are the sounds of home -- a beacon that just might draw them in from miles away.

A snapper larva, often associated with reef or mangrove habitats. Credit: Benjamin Victor, www.coralreeffish.com/larvae.html

Adult fish release their eggs on the reefs. Tides and currents wash the eggs out to sea, which is a safer environment for the young fish to hatch and develop.

Marine scientists used to think the young fish continued drifting until they just happened to find a reef. But research is showing otherwise. By the time they’re the length of a pencil eraser, the fish are strong enough to swim against the current. And before they reach the size of the nail on your little finger, they can hear.

By then, it’s time to start looking for a home. The fish probably use several clues to help them find a reef, including smell. But it’s becoming clear that sound plays a role, too.

A few years ago, for example, researchers built mock reefs off the coast of Australia. They played reef sounds at half the sites, and no sound at the others. Young fish congregated at the noisy sites -- especially those with the sounds of shrimp, which are popular prey. So it seems that the busy sounds of a coral reef are a siren call, luring youngsters to new homes.