The short version
- Scripps researchers played recordings of a healthy reef from an underwater speaker in Kāneʻohe Bay, Oʻahu, for two weeks at a time in 2023 and 2024.
- The site with sound drew 4 to 14 times more fish larvae than a silent control, and the gap held when the two speakers were swapped.
- Coral larvae settled most on artificial structures closest to the speaker, especially ones coated in a living “reef ink”.
A healthy reef is loud, and young fish and coral drifting in open water seem to use that noise to find a home. Scripps Institution of Oceanography researchers tested the idea in Kāneʻohe Bay, Oʻahu, during spawning seasons in 2023 and 2024. An underwater speaker off the island of Moku o Loʻe played recordings of a healthy reef for two weeks at a time. The recordings span a lunar cycle and include fish and snapping shrimp. Thirty-seven artificial structures sat 4.5 m down, between 1 and 42 m from the speaker. The results appear in two papers, in Communications Biology (coral) and Scientific Reports (fish).
Coral larvae settled most on the structures nearest the speaker, and best of all on ones coated in BRINK, a “reef ink” containing living bacteria. Autonomous cameras watching 3D-printed “fish hotels” counted 4 to 14 times more fish larvae at the site with sound than at a control site, and the difference held when the speakers were swapped. To drifting larvae, lead author Aaron Thode said, a lot of reef sound “signals to them that this is a good place to settle.”
We could not open either paper, so sample sizes and statistics are not given here, and nothing yet shows whether the settled coral survives. The work was funded by the US military research agency DARPA, which plans a 50 m hybrid reef with a sound system off Oʻahu this fall.
