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Scientists Are Luring Fish Back to Dead Reefs by Playing Them Sounds From Thriving, Healthy Reefs

The technique has shown promising results, and researchers hope it could be used to restore parts of the Great Barrier Reef.

by Gavin Butler
05 December 2019, 11:00am

Image via Flickr user Beyond Coal & Gas Image Library, CC licence 2.0 (L) and Dauvit Alexander, CC licence 2.0 (R)

This article originally appeared on VICE Australia.

Scientists are hoping underwater speakers could help save the Great Barrier Reef. Or, at least, some of it.

A team of researchers from Australia’s James Cook University and the Australian Institute of Marine Science, alongside researchers from the UK’s University of Exeter and University of Bristol, found that it’s possible to restore life to otherwise dead or degraded reefs through a method known as “acoustic enrichment”: basically, blasting recordings of healthy underwater habitats through loudspeakers to make it sound like there are lots of fish there. Like leaving the TV on to make it sound like someone’s home, or turning up the music to make your house party sound better than it is.

“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,” said Professor Steve Simpson, a marine biologist from the University of Exeter and senior author of the study. “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."

Bob Wong, a professor of Behavioural and Evolutionary Biology at Melbourne’s Monash University, explained that when baby sea organisms hatch from their eggs they need to be able to find their way back to the nearest reef to settle.

“There's good evidence to show that these animals hew in on a whole range of different things to find their way to suitable habitats, including sounds and smells,” he told VICE over the phone. “When you degrade a reef, it starts to sound and smell different, which has an impact on the recruitment of new inhabitants to settle into those reefs. But this exciting and promising piece of research shows that you can actually playback sounds of a healthy reef and it can help to attract recruitment of animals to these degraded habitats.”

The technique was tested on over 30 patches of dead coral throughout the northern Great Barrier Reef over the course of 40 days. When researchers assessed the health of the coral patches after that period, they found that there was a 50 percent increase in species richness, including a diversity of fish from all corners of the food web.

“This gives us some hope that when combined with things like reef restoration and conservation measures, this could be a powerful tool to use to try and recruit animals back to reef areas that might have been degraded,” said Professor Wong. “But of course, it needs to be combined with these other measures as well, because there's no point getting a whole bunch of animals back to an unhealthy reef, because they're probably not going to succeed in that unhealthy environment.”

Catfishing sea life into swimming out to a specific location is one thing, but if steps aren’t taken to reduce coral bleaching and further degradation of those reef areas, then the fish won’t stick around or even be able to survive there for long.

“This research shows a lot of promise, but we also need to think of the bigger picture,” Professor Gordon stressed. “A lot of reefs around the world are facing increasing pressures because of human activities, ranging from overharvesting of commercially important species right through to the potential impacts of climate change. So obviously we need to put in place effective measures to deal with those kinds of things. Otherwise recruiting fish and other organisms back to a reef is futile.”

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