How Do Young Fish Find Their Way?

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How Do Fish Find Their Way?
Hatched in the ocean, larvae may use sound to settle on reefs
By Bennett McIntosh
:: Originally published online September 6, 2017
Oceanus Magazine

A day in the field for Justin Suca begins at 4:45 in the morning, just before the first stars begin to disappear from the sky over the island of St. John. He’ll spend the next five hours motoring around the reefs south of that Caribbean island, retrieving tubular nets full of fish trapped during the night. The fish are much too small to eat or sell, but Suca doesn’t throw them back.

He and other scientists from Woods Hole Oceanographic Institution (WHOI) are there to count tiny larvae, often less than a centimeter long. The nets intercepted the larvae as they made their harrowing trip from the open ocean where they hatched, to the reef where they would settle down and live. Suca and colleagues are there to understand how they find their way home.
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The larvae travel almost blind, swimming overnight through dark waters, so they must rely on other senses. Rich chemical clues about the flora and fauna on a reef can disperse miles through the water, but Suca says the fish would have trouble relying on their noses to guide them home. Smell can travel a long distance, he said, but it’s hard for fish swimming through swirling pockets of odor to discern which direction the smells are coming from without integrating other senses. So Suca is focusing on how the larvae use another sense: sound. 

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