Scientists Mimicked Sounds of Healthy Coral Reefs to Lure Fish to Dead Ones

Imagine your local main street with all of its varied restaurants lined up on either side of the road; it’s usually the restaurants that have the most activity that attract the most passers-by, right? It turns out that the same phenomenon applies to coral reefs and fish, as the latter prefers noisier versions of the former. Which, sadly, turns out to be a major problem when it comes to dead reefs that don’t produce any sound. Scientists may be able to help those dead reefs, however, because new research shows that simply reproducing the sounds of healthy reefs with loudspeakers attracts more fish to dead ones.

In a recent paper published in the journal Nature Communications, which was reported by The Washington Post, researchers say that when they reproduced the sounds of a healthy coral reef from inside of a dead reef, they were able to attract twice as many fish compared to a dead reef that did not emit any artificial sounds of a healthy, active reef.

The experiment took place over the course of six weeks in 2017, near the Great Barrier Reef off the coast of Queensland, Australia. It’s one of many methods scientists are exploring to help rehabilitate coral reefs ravaged by the effects of climate change.

Stephen D. Simpson, a marine biology professor at the University of Exeter and one author of the paper, told The Post that “Healthy coral reefs are remarkably noisy places…” and that “Juvenile fish home in on these sounds when they’re looking for a place to settle.” Knowing this, the team behind the paper constructed three different patches of dead reefs: one that had active loudspeakers producing the sounds of a busy, living reef; one that had dummy loudspeakers that produced no sound; and one that produced no artificial sound, nor contained any dummey speakers.

Graphs showing the number of fish attracted by the “acoustic enrichment.” Nature Communications 

According to the paper, the reef patches with the loudspeakers producing the sounds of a healthy reef increased the development of fish communities, as well as overall species richness. This is one critical component of rehabilitating dead coral reefs because fish are an integral part of their ecosystems. For example, the Atlantic and Gulf Rapid Reef Assessment notes that herbivorous fish are important for coral reef health because they graze on algae that would otherwise grow out of control. Another example is the relationship between clownfish and sea anemones, as the clownfish protect the anemones from predation.

This “acoustic enrichment” (the official term for the process of attracting fish to the reefs with artificial sound) had “a significant positive impact on juvenile fish recruitment” according to the paper. This is especially important because reef fish populations are sustained by an influx of young fish born in the open ocean. The artificial sounds specifically drew in damselfish, which are particularly useful for coral reefs as they provide them with much-needed nutrients and ventilate their inner zones.

Ten hours worth of active coral reef sounds, for reference. 

Looking forward, the authors of the paper say that the goal now is to see if their results will translate to other reef habitats in other parts of the world; they also want to see if they can achieve the same positive results with adult fish as they did with juvenile fish. If their results are verified by further testing, this method of acoustic enrichment could be deployed on a much larger scale in order to help generate a snowball effect, whereby the loudspeakers attract fish populations, which in turn make their own sounds, attracting even more sea life. “Boosting fish populations in this way could help to kick-start natural recovery processes,” Gordon added in his comments to The Post, “[which would counteract] the damage we’re seeing on many coral reefs around the world.”

What do you think of this method for rehabilitating coral reefs? Is this research totally sound in your opinion, or have you seen more effective methods for dealing with this problem? Give us your thoughts in the comments!

Feature image: Lakshmi Sawitri