https://techcrunch.com/2019/12/02/researchers-find-making-a-sick-reef-sound-like-a-healthy-one-could-help-its-recovery/

A new study, published in Nature Communications (via Washington Post), found promising early results from an experiment wherein sounds that you’d hear from a healthy reef are played back at a reef that’s dying. It may sound a bit like a bait-and-switch, but previous research has shown that one way to help reefs that are under duress is to encourage diverse and abundant fish populations, which can help counteract the downward spiral that ultimately leads to reef death.

Over the course of six weeks, researchers from the UK and Australia played audio recordings over speakers installed underwater at dead patches found in Australia’s Great Barrier Reef. The recordings were taken from healthy sections, and included a range of sounds typical to thriving coral communities, including noises made by fish, shrimp, molluscs and other reef-dwellers. These sounds act as cues for young fish looking to settle down and establish communities of their own.