Reef Sounds – Music To Fishes’ Ears?

Study after study reveals that coral reefs worldwide are put under pressure by various human-caused stressors. While reef destruction can be mitigated by maintaining healthy fish populations in the vicinity, the animals tend to avoid dying reefs, forming a spiralling negative trend. In this study, a mixed team of researchers from the U.K. and Australia tested a novel approach for managing reefs in danger of disappearing – playing recordings of healthy reef ecosystems underwater. The basis for this innovation was a set of previous research findings, which showed that sound playback increased the settlement rates of some land animals.

Reef fish populations are sustained by something called recruitment. Here, young fish turn from open waters to settle in attractive reef habitats. The fishes use different sensory cues to detect and navigate to potentially habitable reefs. Quite understandably, degraded reefs smell and sound less attractive to juvenile fishes, and attract many fewer new inhabitants than healthy habitats.

To test their approach, the researchers placed loudspeakers near coral-rubble patches and broadcasted “healthy soundscapes” for 40 days on Australia’s northern Great Barrier Reef. The results were highly promising: 

• significantly more fishes of all major trophic guilds (from herbivores to piscivores) came to the acoustically enriched reefs;
• the recordings led to 2x higher total abundances of juvenile fishes;
• the modified reefs also had 50% greater species richness and diversity. 

The scientists are optimistic that the effects of acoustic enrichment could extend beyond the specific reefs equipped with loudspeakers, as the presence of more fish would increase the attractiveness of the reef even further. Such a method may lead to exponential reef recovery rates if successfully combined with effective habitat restoration and conservation measures.

Animal advocates will surely breathe a sigh of relief as the present study is one of rather few that show a positive change to natural ecosystems with human intervention. In this case, it seems likely that human-created innovation can help bring life back to otherwise damaged reefs, and such a change is exactly what we should be expecting from future scientific endeavours.