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Scientists lure fish to dead reefs using speakers playing healthy coral sounds

Underwater speakers playing healthy reefs noises double the amount of fish on damaged reefs, giving scientists hope that sound could be used to help restore them.

www.abc.net.au|Nick Kilvert

• Fish numbers doubled and species increased by 50 per cent on acoustically "enriched" sites
• Coral polyps have also been found to navigate toward healthy sounding reef, despite not having ears
• Bigger stressors like climate change, pollution and overfishing still need to be addressed

Researchers have used the sounds of healthy reefs to entice fish back to areas where coral has been wiped out on the Great Barrier Reef.

They took recordings of shrimp snapping, fish grunting and other sounds taken from healthy regions of reef and played them on underwater speakers at a bunch of "coral-rubble patch reefs" at Lizard Island.

The number of fish doubled at the sites where they placed the speakers compared with control sites with no audio over the 40-day study period, they reported in Nature Communications.

They also found the number of different types of fish — the species richness — increased by 50 per cent during that time.

The researchers hope their findings may help in restoring some of the ecosystem functions to coral reefs that have suffered bleaching or been hit by cyclones or other impacts, said Tim Gordon, lead author and PhD student from the University of Exeter.

"Attracting fish to a dead reef won't bring it back to life immediately. But recovery is underpinned by fish that can clean the reef and create space for corals to regrow.",  Dr Mark Meekan

To move reef recovery beyond localised applications such as this one, the bigger issues must be fixed, Professor Nagelkerken said.

"It doesn't solve the greater issue of how we are [harming] the oceans via pollution, climate change and ocean acidification, habitat destruction and overfishing," he said.

"If we don't remove those stressors then reef restoration is not going to happen."

The sounds that come from the Northern Great Barrier Reef have got quieter in the last five years, scientists at the University of Exeter have found.

The noises, which are made by sea creatures, help young fish find their way home.