Deteriorating Great Barrier Reef hushed: Young fish no longer hear their way home

April 30, 2018, University of Exeter

Degraded coral reefs are far quieter than five years ago, and no longer sound like a suitable habitat to young fish searching for a place to live and breed, according to research published today in Proceedings of the National Academy of Sciences.

Baby fish looking for a home can use noisy coral reef sounds including snapping shrimp clicks, damselfish chirps, and clownfish chattering to locate and select suitable habitat. But that "coral reef orchestra" has been quietened following recent cyclone and coral-bleaching damage on the Great Barrier Reef, raising fears that young fish may no longer hear their way home.

An international team of scientists, led by the University of Exeter, carried out field experiments on the Northern Great Barrier Reef and found that reefs sound much quieter and less acoustically diverse than they did before three years of cyclones and coral bleaching.

The soundscapes of these recently-degraded reefs are less attractive to juvenile fishes attracting 40% fewer fish compared to the sound of previous healthy reefs.

Lead author Tim Gordon, a marine biologist at the University of Exeter, said: "It's heart-breaking to hear. The usual pops, chirps, snaps and chatters of countless fish and invertebrates have disappeared. The symphony of the sea is being silenced."

This loss of attractiveness of reef sounds to fish in the sea could have devastating consequences for reefs.

Fish communities are instrumental to maintaining healthy reefs by removing algae, facilitating coral growth, contributing to nutrient cycles and keeping food webs in balance. Damaged reefs with healthy fish populations recover faster than reefs that have lost their fish.

Harry Harding, co-author from the University of Bristol, explains: "If fish aren't hearing their way home anymore, that could be bad news for the recovery prospects of reefs. Fish play critical roles on coral reefs, grazing away harmful algae and allowing coral to grow. A reef without fish is a reef that's in trouble."

Read more at: