The Dawn Chorus Underwater

Our regulators are so noisy when we breathe underwater, it's about the only sound we hear. But if you could listen carefully, you might just hear the sounds of the fish choir.

Most of this underwater music comes from soloist fish, repeating the same calls over and over. But when the calls of different fish overlap, they form a chorus.

Robert McCauley and colleagues at Curtin University in Perth, Australia, recorded vocal fish in the coastal waters off Port Hedland in Western Australia over an 18-month period, and identified seven distinct fish choruses happening at dawn and at dusk.

Sound plays an important role in various fish behaviors such as reproduction, feeding, and territorial disputes. Nocturnal predatory fish use calls to stay together to hunt, while fish that are active during the day use sound to defend their territory.

"You get the dusk and dawn choruses like you would with the birds in the forest," says Steve Simpson, a marine biologist at the University of Exeter, UK. Recordings were captured by two sea-noise loggers: the first positioned near the Port Hedland shore and the second 21.5 kilometers (12.5 miles) away in offshore waters.

Listening to choruses over a long period of time allows scientists to monitor fish and their ecosystems, particularly in low visibility waters.

"We are only just beginning to appreciate the complexity involved and still have only a crude idea of what is going on in the undersea acoustic environment," says McCauley.

(Journal reference: Bioacoustics, DOI: 10.1080/09524622.2016.1227940). (From an article in New Scientist)