Quiet Please, the Fish Are Flirting

Fish that fart together stay together.

Published June 21, 2017

In an ocean full of clicking shrimp and singing whales, fish are often imagined as the silent actors. Fish use motion, color, and chemicals to communicate, but they lack the iconic mewl of a cat or trill of a bird. Yet in reality, many fish chat constantly to mark their territories or find mates. And all of our noise—from seismic surveys to boat motors—is making it much more difficult for fish to hear one another.

The fact that some fish make noise has been known for a while, says Xavier Mouy, a biologist at the University of Victoria, in British Columbia. But few people have been interested in studying the phenomenon. So this summer, Mouy and his colleagues will gather underwater recordings to determine which fish are making sounds, and why.

“Of the 400 species in British Columbia’s waters, 22 are known to make sounds,” he says. “But there are probably a lot more we don’t know about.”

Fish tend to talk in one of two ways. Some use their bones: catfish make sounds by moving the vertebrae in their spine, while seahorses knock the bones of their skull together. Others, such as rockfish, quickly contract specialized sonic muscles around their swim bladder to make low-frequency grunting noises.

In primitive fish such as herring, the swim bladder is connected to the digestive system, so a sort of buzzing noise is produced when air is forced out the anus. Lawrence Dill, at Simon Fraser University in Burnaby, British Columbia, and his colleagues won the Ig Nobel prize in 2004 for discovering these “fast repetitive ticks,” or FRTs. (Yes, Dill knew exactly what he was doing when he named them.)

Fish communicating in the Fraser River delta in British Columbia. Audio courtesy of JASCO Applied Sciences

Herring tend to fart more often at night, and when they are in large groups. Dill suggests they use the farts to communicate, and keep their school together in the dark.

But other fish may use their noises differently. To find out how, Mouy is deploying a series of underwater listening stations off Canada’s west coast. The first was installed in the Strait of Georgia in early May, and 14 more will be installed over the next year. The listening stations include high-definition cameras, sonar, and sensitive hydrophones. The combination of sensors will allow Mouy to link the sounds to a particular species and behavior, and build a catalog of fish talk.

Audio recordings of herring FRTs. Audio courtesy of Ben Wilson, Scottish Association for Marine Science

Mouy says the recordings could eventually help fish researchers keep track of what’s going on under the sea. “We want to see if we can know where the fish are and what they are doing just by listening to the ocean,” he says.

Dill isn’t convinced that the noises will be useful for monitoring—they depend too much on a fish’s particular situation. But recording fish communication will help us understand how fish are affected by noise pollution. “Knowing how fish communicate will help us know how we’re disrupting it,” he says.

Recordings of fish communication in the Straight of Georgia, off Hornby Island. Audio courtesy of JASCO Applied Sciences

Having a deep understanding and appreciation of fish communication could be good for the fish, but, occasionally, it’s also important for people.

In 2004, researchers in Sweden used their awareness of fish farts to defuse a diplomatic row. For years, the Swedish navy had assumed that herring farts were the sound of Russian submarines lurking in Swedish waters, which led Prime Minister Carl Bildt to write a nasty letter to President Boris Yeltsin. But the researchers were able to identify the navy’s suspicious recordings as flatulent herring, and a crisis was averted.