Playing underwater ‘music’ attracts young fish to degraded coral reefs

Whether it’s the “crackle of snapping shrimp” or the swishing sounds of fish passing by, a healthy coral reef tends to be quite a noisy place. These are sounds that young fish are attracted to once they have hatched and spent their larval stage in the open ocean.

The problem is that once a reef degrades, which is something that is happening worldwide due to warming oceans, then the reef smells and sounds less attractive to the juvenile fish. Those fish will then opt to settle elsewhere, causing the reef to degrade further.

With this in mind, a team of scientists came up with the idea of playing underwater sounds along degraded portions of Australia’s Great Barrier Reef that would replicate the usual noises heard on a healthy, active reef. To their great surprise, the scientists found that the fish were attracted to the music and more willing to stick around.

As reported in Treehugger, the reefs were given one of three experimental treatments. They either had no loudspeaker, a dummy loudspeaker (to control for visual cues that might affect fish behaviors), or a real loudspeaker (a.k.a. “acoustic enrichment treatment”) that played reef sounds. Playback occurred for 40 consecutive days, always at nighttime, which is when fish settlement typically occurs. 

At the end of the experiment, the researchers found that acoustically-enriched reefs had attracted fish at a faster rate than non-enriched reefs, with twice as many juvenile damselfishes on acoustically enriched reefs when compared to the two control group reefs. Biodiversity also increased by 50 percent, with more than just damselfishes attracted to the sound.

Although the presence of fish alone cannot restore a coral reef to good health, study author Dr. Mark Meekan explained that “recovery is underpinned by fish that clean the reef and create space for corals to regrow.” The study shows that acoustic enrichment could “facilitate a ‘snowball effect’, whereby other fish respond positively to communities established earlier, causing further increases in the settlement.”

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