BioEd Online

After months roaming the waves as larvae, it seems that fish tune into the sounds of home when they want to settle down. A study on Australia's Great Barrier Reef has shown that the crackle of shrimp and the calls of fellow fish serve to attract tropical tiddlers.

Researchers working near Lizard Island, 240 kilometres north of Cairns, Queensland, set up 24 fake reefs made from dead coral. Half the reefs contained submersible speakers that played a cacophony of genuine reef noise consisting of snapping shrimp and other fish. They found that noisy reefs attracted a far greater number of fish than those that were silent.

"We knew that they were attracted to light traps. But no one had shown that the fish located sound and could be encouraged to settle depending on it," says Stephen Simpson of the University of Edinburgh, UK, who led the research.

Around 80% of the fish attracted to the reefs were cardinalfish (apogonids), and most of the remainder were damselfish (pomacentrids). But noisy reefs also attracted a wide range of less common fish, the researchers report in Science¹.

Din of the deeps

Simpson suggests that sound could be a key tool for developing or restocking fisheries. Commercial divers gathering tropical fish often use cyanide, which destroys coral. A 'pied piper' approach to collecting or moving fish would be preferable, says Simpson.

However, collecting fish indiscriminately may affect the stability of the reef as a whole, warns Ameer Abdulla of the World Conservation Union's Global Marine Programme. "You have to be very careful with interpreting these results. These are experimental tests in a restricted system."

The total number of fish out there is going to stay the same, wherever you move them, Abdulla adds. And although he welcomes the research, he asks: "Which area do you choose to protect or enhance?".

Nevertheless, Simpson suggests that collecting very young fish could aid conservation efforts: reef fish typically have a mortality rate of 70% in the first 2 to 3 days of juvenile life.

The study also highlights the importance of monitoring adverse effects of noise pollution, says Simpson, who is currently studying the Straits of Hormuz in the Gulf. These waters carry a quarter of the world's oil shipments and he is investigating whether fish are attracted to or repelled from certain places by tanker noise.