Soundtrack attracts fish to ailing coral reefs
Scientists use loudspeakers to mimic healthy sounds, which lures animals
The desperate search for ways to help the world’s coral reefs rebound from the devastating effects of climate change has given rise to some radical solutions.
British and Australian researchers have rolled out an unorthodox strategy that they say could help restoration efforts: broadcasting the sounds of healthy reefs in dying ones.
In a six-week field experiment, researchers placed underwater loudspeakers in patches of dead coral in Australia’s Great Barrier Reef and played audio recordings taken from healthy reefs. The goal was to see whether they could lure back the diverse communities of fish that are essential to counteracting reef degradation.
The results were promising, according to the researchers. The study, published in the journal Nature Communications, found that twice as many fish flocked to the dead coral patches where healthy reef sounds were played compared with the patches where no sound was played.
“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,” said Steve Simpson, a marine biology professor at the University of Exeter and a senior author of the study. “Juvenile fish home in on these sounds when they’re looking for a place to settle.”
According to the study, the number of species present in the reef patches where healthy sounds were played increased by 50 per cent over the other patches. The new fish populations included species from all parts of the food web, such as scavengers, herbivores and predatory fish. Importantly, the fish that arrived at the patches tended to stay there.
“Reefs become ghostly quiet when they are degraded, as the shrimps and fish disappear,” Simpson said, “but by using loudspeakers to restore this lost soundscape, we can attract young fish back again.”
The technique, if it can be replicated on larger scales, could offer scientists another tool to revive coral reefs around the world that have been ravaged by climate change, overfishing and pollution in recent years. The researchers worked from October through December 2017 in a lagoon in the northern part of the Great Barrier Reef that has a large, shallow reef that runs along the coastline.
At the start of fish recruitment season, when fish spawn and mature, the team built 33 experimental reef patches out of dead coral on open sand about 27 yards from the naturally occurring reef. They then fixed underwater loudspeakers to the centre of the patches, angling them upward to ensure the sound was distributed in all directions evenly.
Over the course of 40 nights, the team played recordings from a healthy reef in some of the patches. In other patches, they used dummy speakers that emitted no sounds, and they left a third group of patches untouched.
The process, called “acoustic enrichment,” had a “significant positive impact on juvenile fish recruitment throughout the study period,” the researchers wrote. The acoustically enriched reefs attracted fish faster and maintained them longer than the reefs without a healthy soundtrack, according to the study.