It sounds like the setup to a joke, not a genuine scientific question. But yes — fish really do fart. Not only that, one particular species farting in the dark waters off Sweden's coast once triggered a real, honest-to-goodness Cold War military scare, with the Swedish Navy convinced for years that Soviet submarines were secretly infiltrating their waters.
The real story is even stranger — and more fascinating — than the punchline suggests. It's a genuine, peer-reviewed piece of science that even won an Ig Nobel Prize, and it reveals something surprisingly sophisticated about how fish communicate with each other in complete darkness.
Meet the Herring, and Its Very Unusual Party Trick
The fish at the center of this story is the herring — a small, silvery species found in massive schools throughout the North Atlantic and Pacific Oceans. Herring are famous for traveling in enormous, tightly coordinated groups, sometimes numbering in the millions, moving and turning almost as a single organism. Scientists had long wondered how such enormous schools managed to stay so precisely coordinated, especially at night, when visual cues would be essentially useless.
The answer, it turns out, involves a genuinely unusual biological mechanism. Herring have a swim bladder — a gas-filled internal organ most fish use to control their buoyancy in the water. What makes herring unusual is that their swim bladder has a direct connection to the anal duct, an anatomical feature not found in most other fish species. This means herring can gulp air at the water's surface, store it in their swim bladder, and then, when needed, release that air in a controlled burst through a small duct near their tail.
That release produces a distinctive, high-pitched popping or buzzing sound — one researchers eventually gave a formal, delightfully on-the-nose scientific name: Fast Repetitive Tick, or FRT for short. Yes, the acronym is exactly what it looks like, and yes, the scientists involved were fully aware of the joke when they named it.
Not Digestion — Communication
It's worth being precise here, because the mechanism isn't quite what "farting" technically implies in most animals. In most creatures, flatulence is a byproduct of digestion — gas produced by the breakdown of food in the gut. Herring farts work differently. The air being released hasn't come from digesting food at all; it's air the fish deliberately gulped from the surface and stored specifically for later release. It's less an involuntary digestive byproduct and more a deliberate, controlled biological signal — closer to a purpose-built communication tool than an accident of biology.
Researchers Robert Batty, Ben Wilson, and Larry Dill first documented this phenomenon formally after studying Pacific and Atlantic herring populations in both Canada and Scotland. Batty, working at the Scottish Association for Marine Science in Oban, described first noticing the phenomenon while monitoring captive herring overnight: "We heard these rasping noises at night. They sounded like high-pitched raspberries." Curious, the research team investigated further and discovered, via careful video analysis, that the sound was directly linked to small bubbles being expelled from the fish's anal duct region.
What they found next was the genuinely fascinating part: this wasn't random or incidental. The pulsing sounds occurred far more frequently at night than during the day, and the frequency of the sounds increased significantly when more herring were packed closely together in one place. Critically, the sounds appeared completely unrelated to feeding behavior or the fish's access to surface air, ruling out digestion or simple biological necessity as the explanation.
The leading scientific theory is that herring use these bursts of sound specifically to help coordinate and maintain their tightly packed schools during nighttime hours, when visual signals — which fish rely on heavily during the day — become effectively useless in the dark. By producing a burst of sound other herring can detect, individual fish can help the entire school stay coordinated and close together without needing to see each other, all while staying quiet enough not to attract nearby predators, since the frequency range of the sound is thought to fall outside what most predator species can easily detect.
In short: fish farting in the dark may function as a sophisticated, purpose-built communication system, allowing massive schools to stay safely together through the night.
When Farting Fish Started a Cold War Panic
Here's where the story takes its strangest and most unexpected turn. Starting in 1982, the Swedish Navy began detecting mysterious, unexplained underwater acoustic signals near their coastline. Given the political climate of the Cold War and Sweden's proximity to Soviet naval territory, officials grew seriously concerned that Soviet submarines were secretly infiltrating Swedish waters, deliberately evading detection.
This wasn't treated as a minor curiosity — it became a matter of genuine national security concern, sparking real investigations, heightened naval readiness, and years of uncertainty about whether Sweden's waters were being quietly breached by a hostile foreign power. For years, the mystery remained unresolved, contributing to genuine geopolitical tension during an already tense period in Cold War history.
The eventual explanation, once uncovered, was almost anticlimactic in the best possible way. Marine biologist Magnus Wahlberg eventually connected the mysterious acoustic signals to the exact same FRT sounds Batty's team had documented in herring. To test his theory, Wahlberg reportedly purchased a herring from a local store and physically squeezed its swim bladder, recording the resulting sound and comparing it directly against the mysterious naval recordings.
The similarity was striking enough that it helped convince Swedish naval officials the "threat" wasn't Soviet submarines at all — it was simply large schools of herring, going about their nightly business of farting to stay together in the dark. What had genuinely worried an entire country's naval defense apparatus for years turned out to be a completely natural, harmless act of fish communication.
A Well-Earned Ig Nobel Prize
The scientific significance of this discovery didn't go unrecognized. In 2004, the research into herring communication through farting was awarded the Ig Nobel Prize in Biology — a genuine (if intentionally tongue-in-cheek) award presented annually at Harvard University to honor real, peer-reviewed scientific research that, in the words of the prize's own mission, first makes people laugh, and then makes them think.
Far from being dismissed as a silly curiosity, the herring fart research represented a genuinely important discovery about acoustic communication in schooling fish — a topic with real relevance to marine biology, given how little scientists still know about how large fish populations coordinate their movement and behavior. As one of the researchers involved, Magnus Wahlberg, later noted, there are more than 30,000 known species of fish, and scientists have only carefully studied the acoustic behavior of a small handful of them. There's very likely a great deal more still waiting to be discovered.
The Takeaway
So yes — fish really can fart, and for herring specifically, that fart is doing genuine biological work: helping massive schools stay coordinated and safe through the darkness of night, using a sound so effective at mimicking a threat that it once had an entire country's navy convinced they were under stealth attack from a rival superpower.
It's a genuinely great reminder that some of the strangest, funniest-sounding facts in nature often turn out to have real, serious scientific substance behind them — and that even something as silly-sounding as "farting fish" can end up quietly shaping international military history.
Sources
Don't miss an article or video. Subscribe to Weekly Bites, our community newsletter.