- Playing sounds of healthy coral reefs can attract young fish to degraded, abandoned coral reefs in the northern Great Barrier Reef, a new study has found.
- Researchers placed underwater loudspeakers in patches of degraded coral reefs and compared them with two kinds of identical patches: some that had dummy loudspeakers that looked just like the functional loudspeakers, and some without any loudspeakers and sound.
- Coral patches that blared sounds of healthy corals had both greater abundance and variety of reef fish species compared to the other two control groups.
- Boosting fish populations using sounds of healthy coral reefs has the potential to help nurse degraded reefs back to health, researchers say.
A healthy coral reef, with its vibrant community of colorful corals and fishes, is not just a visual treat; it’s also a rich medley of sounds. Previous studies have shown that these sounds have an important role to play — the symphony of pops, grunts, crackles, buzzes and scrapes in the reefs draws in young fish looking for a new reef home.
Now, a new study has found that playing the sounds of healthy coral reefs can attract young fish to even degraded reefs in the northern Great Barrier Reef. Increasing the fish population in this manner, or “acoustic enrichment,” has the potential to help nurse degraded reefs back to health, researchers say.
“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,” Steve Simpson, a co-author of the study and a professor at the University of Exeter, U.K., said in a statement. “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.”
In 2016 and 2017, unusually hot ocean waters triggered two severe mass bleaching events across the Great Barrier Reef. Wide stretches of corals expelled their colorful algae, leaving the corals severely stressed or dead. Such reefs usually lie abandoned and silent.
To see if sounds recorded from previously healthy coral reefs could attract fish to degraded reefs, marine researchers placed underwater loudspeakers in patches of degraded corals in the northern Great Barrier Reef between October and December 2017. They compared these patches to control patches of degraded corals that either had dummy loudspeakers that looked just like the functional loudspeakers, or did not have any loudspeakers.
The study found that coral patches that blared sounds of healthy corals had both greater abundance as well as variety of reef fish species compared to the other two control groups. This, researchers say, suggests that it’s the sound of healthy reefs rather than the visual cues of the presence of additional structures like loudspeakers that was drawing in the fish.
Healthy coral reefs and fish are mutually dependent on each other. While reefs provide fish and other marine animals with food, as well as nooks and crannies to find shelter in and reproduce, several fish species in turn graze and keep reef surfaces clean, providing new sites for coral larvae to settle and grow.
“Fish are crucial for coral reefs to function as healthy ecosystems,” Tim Gordon, lead author of the study and a doctoral student at the University of Exeter, said in the statement. “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.”
Just luring in more fish with sound won’t save coral reefs, the researchers add, but it’s a hopeful start. There’s also a lot that needs to be uncovered. The current study, for instance, could not tease apart what sounds are most effective at attracting fish, and questions remain about whether different sounds could attract different kinds of fish, and whether the fish that come to the reefs continue to stay and draw in other fish over time.
“Acoustic enrichment is a promising technique for management on a local basis,” Andy Radford, a co-author of the study from the University of Bristol, U.K., said in the statement. “If combined with habitat restoration and other conservation measures, rebuilding fish communities in this manner might accelerate ecosystem recovery. However, we still need to tackle a host of other threats including climate change, overfishing and water pollution in order to protect these fragile ecosystems.”
Gordon, T. A., Radford, A. N., Davidson, I. K., Barnes, K., McCloskey, K., Nedelec, S. L., … Simpson, S. D. (2019). Acoustic enrichment can enhance fish community development on degraded coral reef habitat. Nature Communications, 10(1), 1-7. doi:10.1038/s41467-019-13186-2