That sounds a bit fishy

Young fish can be attracted to degraded coral reefs by the sounds of healthy reefs, new research suggests.

Australian and British scientists placed underwater loudspeakers on patches of dead coral on Australia’s Great Barrier Reef and found that “acoustic enrichment” doubled the number of fish in the area compared with equivalent patches where no sound was played. And the fish stayed.

The technique works by regenerating the sounds that are lost when reefs are quietened by degradation and this “could help to kick-start natural recovery processes”, according to Tim Gordon from the University of Exeter, UK, the lead author of a paper in the journal Nature Communications.

Exeter colleague Steve Simpson says healthy coral reefs are “remarkably noisy places”.

“[T]he crackle of snapping shrimp and the whoops and grunts of fish combine to form a dazzling biological soundscape. Juvenile fish home in on these sounds when they’re looking for a place to settle.

“Reefs become ghostly quiet when they are degraded, as the shrimps and fish disappear, but by using loudspeakers to restore this lost soundscape, we can attract young fish back again.”

Attracting fish to a dead reef won’t bring it back to life automatically, says co-author Mark Meekan from the Australian Institute of Marine Science, but recovery is underpinned by fish that clean the reef and create space for corals to regrow.