Broadcasting an Underwater Invitation to Fish

"Healthy coral reefs are remarkably noisy places -- the crackle of snapping shrimp and the whoops and grunts of fish combine to form a dazzling biological soundscape."
"Juvenile fish home in on these sounds when they're looking for a place to settle."
"Reefs become ghostly quiet when they are degraded, as the shrimps and fish disappear. But by using loudspeakers to restore this lost soundscape we can attract young fish back again."
Steve Simpson, marine biology professor, University of Exeter

Marine biologist Tim Gordon deploys an underwater loudspeaker on a coral reef. (University of Bristol)

"There's no way you could hear those [waves hitting a shoreline] in a healthy reef, because they'd just be drowned out by the diversity and abundance of other sound types going on."
"There's this constant crackle of shrimps clicking their claws, and invertebrates making noise as they scrape along the bottom."
"When we made the patches sound like they were healthy, we discovered … twice as many fish came back and settled onto these habitat patches, than when we didn't do anything to the sound."
"Fish are crucial for coral reefs to function as healthy ecosystems ... Boosting fish populations in this way could help to kick-start natural recovery processes, counteracting the damage we're seeing on many coral reefs around the world."
"[It's important that] we remove the original stressor that caused the damage in the first place — in most instances worldwide, that is climate change and warming seas." 
"Without strong and decisive action on carbon emissions, any reef restoration will ultimately be fruitless."
Tim Gordon, marine biologist  , University of Exeter

Fish and other sea-life settle on coral reefs, leaving them teeming with life. (Isla Keesje Davidson/University of Bristol)

"Acoustic enrichment is a promising technique for management on a local basis. However, we still need to tackle a host of other threats including climate change, overfishing and water pollution, in order to protect these fragile ecosystem."

"We tracked the experimental reefs for 40 days. Whilst we can't necessarily tell if exactly the same individuals remained, it is certainly true that there were increasing numbers of both individuals and of species across that time, so most likely those arriving were staying."

"In that time frame, it was probably a little soon for them to start breeding - future work would ideally monitor reefs for even longer, as ultimately that is one of the key measures that will be important."

Andy Radford, professor in behavioral ecology, University of Bristol 

In a six-week field experiment British and Australian researchers have thought up a strategy they feel might aid in coral reef restoration efforts. This, to add to efforts by marine biologists to help restore failing coral reefs throughout the world, deemed the effect of climate change. In this experiment, the researchers placed underwater loudspeakers within areas of dead coral along Australia's Great Barrier Reef, to play audio recordings of healthy reefs to determine whether diverse communities of fish that normally inhabit such reefs could be lured back, in the process begin to counteract reef degradation.

The study was published in the journal Nature Communications, finding twice as many fish tended to flock to the dead coral patches from which healthy reef sounds were emanating. In comparison, patches where no sound was played attracted fewer fish to return. The study points out the number of species present in the reef patches where healthy sounds were broadcast increased by fifty percent in comparison to other nearby patches, with the new fish populations including species from all areas of the food web.

An underwater loudspeaker on a coral reef

Fish such as scavengers, herbivores and predatory fish were all represented as returnees. And what seemed even more promising is that those fish that arrived at the patches appeared to remain there. Should the technique, replicated to ensure its accuracy and on larger scales, prove to be as positive in its results, it could represent yet another methodology to revive coral reefs globally, alarmingly ravaged by overfishing, pollution and climate change.

Working from October through to December of 2017 in a lagoon located in the northern part of the Great Barrier Reef where a large, shallow reef runs along the coastline, the researchers fixed underwater loudspeakers to the centre of the patches at the start of fish recruitment season when fish spawn and mature. Thirty-three experimental reef patches were built and placed on open sand, some 27 yards from the naturally-occurring reef. The loudspeakers were angled upward to distribute sound evenly in all directions.

Ocean fish and other marine species depend on healthy coral reefs.  jadhav vikram

The researchers sounded the recordings from a healthy reef in some of the patches, while in other patches they used speakers emitting no sounds. A third group of patches was left  untouched. The "acoustic enrichment" process had a "significant positive impact on juvenile fish recruitment throughout the study period" of 40 nights, the researchers wrote in their published study.

It was satisfactorily ascertained that the reefs that were 'acoustically enriched' attracted fish faster, while maintaining them longer than the reefs absent a soundtrack of healthy reefs, according to the study results.