A new study published in the journal Biology Letters is the first to document that fish larvae produce sound.

The authors of the study – Erica Staaterman, Dr Claire Paris, and Dr Andrew Kough, all from the University of Miami – carried out field and lab experiments to listen to larval gray snapper (Lutjanus griseus).

Also known as the mangrove snapper, it is an economically valuable fish that spend first 30 days of life as pelagic larva before settling in shallow sea grass beds.

In the field experiments, the researchers set a drifting in situ chamber, called DISC, equipped with audio and video recording systems, near Fowey Rocks lighthouse in the northern Florida Keys to record larval orientation behavior in the pelagic environment. In total 58 deployments were conducted, 27 during the day and 31 at night.

They also recorded sounds in a lab setting to confirm that the sounds observed in the field were from gray snapper larvae.

The team also referred to the public sound archive at the Macaulay Library to compare the larval sounds to those produced by adult gray snappers.

They observed that larvae produced ‘knocks’ and ‘growls’ in the range of 200–800 Hz, which is within the hearing range of most adult fish.

“Although many adult fishes produce sounds, no one has previously considered that larvae, too, may be sound producers,” Dr Paris said.

“This is the first study to show that fish larvae have an acoustic repertoire.”

“This is a true discovery as it reveals the existence of a communication system for young fish larvae.”

The gray snapper larvae produced ‘knock’ and ‘growl’ sounds during 70 percent of the nighttime trials, and none of the daytime trials.

The team suggests these sounds may help larvae maintain group cohesion in the dark.

“It was a fantastic surprise to listen to the recording and hear that the larva itself was emitting sound,” Dr Paris said.

“Communication between larvae could allow them to maintain group cohesion, which is critically important for faster swimming, finding navigational signals and settlement cues, and better survival during the pelagic phase.”

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Erica Staaterman et al. 2014. First evidence of fish larvae producing sounds. Biol. Lett., vol. 10, no. 10; doi: 10.1098/rsbl.2014.0643