Einstein Science Reporting for Kids
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American Association for the Advancement of Science

How real Nemos find their way home

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A coral reef is an extremely loud place. The sounds of snapping shrimp claws, grinding fish teeth and other fish noises can be heard from kilometers away. Scientists have now discovered that this noise helps young fish that have drifted away from the reef find their way home.

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After baby fish, or "larvae," hatch from their eggs on the reef, they get carried out to sea by ocean currents. At this young age the larvae just look like "little blobs," according to Stephen Simpson, a scientist at the University of Edinburgh in the United Kingdom.

Simpson and his colleagues have now learned that after the larvae have grown a little and become strong swimmers, they listen for noises to find their way back to the reefs. The researchers report their findings in the 8 April issue of the journal Science.

"We think the sounds of the reef give a lot of information about what it's actually like there," Simpson said.

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To investigate the role that noise might play in guiding the fish larvae home, the researchers built 24 artificial reef patches on the Great Barrier Reef, off the coast of Australia. On half of the reef patches they placed speakers broadcasting reef noise.

The ruckus included snapping shrimp, which sounds like frying bacon, and sounds that fish make by sending air through different chambers of their swimbladder, an inflatable sac that helps them float. For example, some fish grind their back teeth, and this noise is then amplified by the swimbladder.

The researchers found that two common types of reef fish larvae, called cardinalfish and damselfish, settled in greater numbers on the noisy reefs than on the quiet reefs. The larvae seemed to have been attracted by the sounds.

Humans drilling for gas and oil and also cruising past in large ships also make a lot of noise near certain reefs. Simpson wonders whether these sounds might interfere with the fishes' ability to find reefs to settle on.

People might also be able to use fishy noise as a way to advertise areas that they want to draw fish to. For example, underwater speakers playing the right kind of sounds might help attract fish to protect areas for conservation. And, fisherman could also use this form of advertising to entice fish to their fishing grounds.