Grunts, murmurs and songs – The mysterious sounds with which fish communicate

Fish produce a variety of sounds for a variety of reasons: to ward off competitors, to sound an alarm, and even to attract potential mates.

To eavesdrop on the marine world, scientists use underwater microphones, so-called hydrophones. Technology invented in World War II to detect submarines has helped us hear the ways fish talk to each other in the depths of oceans, rivers and lakes, reports the BBC News.

From 34,000-35,000 species of ray-finned fish, which include cod, tuna, trout and salmon, only about 4% have been studied for sound production. But research by Aaron Rice, a marine biologist at Cornell University in New York, shows that we’ve barely scratched the surface of the mysterious world of fish communication. Up to two-thirds of fish could make noises underwater, he says.

Small on the eye, loud on the sound

In February 2024, researchers in Germany discovered a tiny transparent fish called Danionella cerebrum, which produces a sound as loud as a gunshot. They discovered this after hearing mysterious “clicks” coming from the fish tanks in their lab. The 12-millimeter-long fish uses an organ called a swim bladder to produce sounds that reach 140 decibels in the water around it, which you can hear in the video below. Only male fish produce these sounds, which may be used to establish a sort of hierarchy in fish tanks.

Fish tend to make sounds for reproductive and territorial reasons. These sounds sound much clearer to fish than to us. “Sound in water travels about five times faster than it does in air,” says Audrey Luby, an ecologist at the University of Florida who studies fish bioacoustics.

“If we put our heads in a pool and try to figure out where a sound is coming from, we have a really hard time. Fish, on the other hand, can glean directional information from underwater sounds.”

Luby has collected over 1,200 of these sounds into one online library called FishSounds. Among them, some sounds – and the behaviors they signal – stand out.

Love calls

The frogfish they may have a bad reputation as “slimy and ugly,” but they’re “amazing singers,” says Luby, who studies frogfish in Florida Bay.

While in their breeding season, males build nests in coastal estuaries and rocky shores, where they “sing” loudly to attract females to their nest or to warn other males to back off, Luby says. “Songs” usually begin with a grunt followed by a series of “boops”.

The Damsel fish, famous for their bright colors, are also… amorous troubadours. The Ambon species, which lives on coral reefs in the western Pacific, takes its courtship a step further. Scientists studying a reef in Taiwan recorded a distinctive high-pitched sound, like a wiper on dry glass, when these fish tried to attract mates.

The male cods they also try to cajole their potential mates with a series of taps and grunts, which become increasingly frantic the more aroused they become.

Signals with… gases

Some species of the family of Klypeidonwhich includes the herrings and them sardines, use sounds from their gastrointestinal tract as a way to keep in touch with their flocks. To put it simply, they are lost.

In fact, the (humorous) scientists who study these sounds called them Fast Repetitive Ticks, for short FRT (from fart).

According to a study of Pacific herring, most of these sounds were not affected by what the fish ate or whether they had direct access to air. This ruled out digestive gas or air swallowing to produce FRT sounds. Instead, it appears that animals expel gas to produce pulsating sounds. The sounds, which can last several seconds, tend to be produced at night and may serve a social purpose, helping the fish maintain cohesion within schools, Luby says.

Predator avoidance

Some fish use sound as a tool to create distance, rather than attract other fish. For example, a species catfish it makes a loud screeching sound to scare off predators, shaking the spines of its pectoral fins into grooves on its shoulder. Another type of fish, o ball carrierproduces a series of “short pops” when threatened, which are heard for about 85 milliseconds.

Recently scientists from the Swedish University of Agricultural Sciences found evidence that the skates – which belong to the chondrichthyan family that includes sharks – also make noises. It was previously thought that sharks and their relatives only made passive feeding-related noises. But the researchers recorded a series of loud, high-frequency “clicks” in the sled species, which they believe may be a response to danger.