Red Herring
During the Cold War, Sweden's military detected mysterious submarine sounds in their waters for over a decade, triggering military operations and international tensions. Scientists eventually discovered the 'typical sound' was actually thousands of herring fish releasing air bubbles through their anal canals—essentially fish farts—not Soviet submarines.
Summary
In 1981, a Soviet submarine ran aground on Sweden's coast, alarming the Swedish public and government about potential Soviet invasion. The incident prompted Sweden's military to invest in underwater surveillance using hydrophones to detect submarines in the Baltic Sea. Beginning in 1982, the military reported detecting Soviet submarines repeatedly throughout the 1980s, with commanders claiming to hear a distinctive 'typical sound' that definitively indicated submarine presence. For 15 years, this sound remained classified and was never analyzed by independent scientists. Military responses included dropping explosives from helicopters, deploying nets across harbors, and creating elaborate reporting systems to track submarine sightings. As Cold War tensions escalated, Swedish Prime Minister Carl Bildt even sent an angry letter to Boris Yeltsin demanding Russia stop invading Swedish waters, though Yeltsin denied any Soviet submarine activity. In 1996, Magnus Valberg, a university student studying underwater biological sounds, and his mentor Håkon Vesterberg were recruited into a top-secret government committee to identify the mysterious sound. When finally played the classified recording, both scientists immediately recognized it as a biological sound rather than mechanical submarine noise. Their hypothesis: the sound came from herring fish expelling air from their swim bladders through a direct canal to their anal opening. After testing dead herring in laboratories, then wild herring in fishing nets, they confirmed the 'typical sound' matched the acoustic signature of thousands of herring farting in unison. Their 1999 findings revealed that over a decade of military operations, international diplomatic tensions, and substantial government expenditures had been triggered by fish waste gas. The military's failure to consult independent marine biologists, combined with institutional confirmation bias where military officials interpreted ambiguous sonar data as evidence supporting the submarine theory, perpetuated the false identification for years.
About this episode
A deep-sea Cold War mystery with subs and bombs and science.
Key Insights
- Magnus observed that the Swedish military kept things secret which prevented open scientific discussion, and maintained a top-down culture where authorities' explanations became accepted without scrutiny, allowing people to 'easily wind yourself up in some kind of explanation.'
- When the military used sonar to investigate the sound, they observed on their screen that the acoustic object would split into two, then four, then recombine back to one—which they interpreted as evidence of highly advanced Soviet submarines, when they were actually seeing schools of herring dividing and reuniting.
- Håkon and Magnus immediately recognized the classified 'typical sound' as biological rather than mechanical after hearing it once, despite military experts being unable to identify it after 15 years, suggesting the military lacked basic marine biology expertise.
- The herring's unique anatomy—possessing a direct canal from swim bladder to anal opening—allows it to release air bubbles as a propulsion method, unlike most fish which release air silently through gills and bloodstream.
- For over a decade, the Swedish military's response to herring sounds included dropping explosives from helicopters, deploying metal nets across harbors, and maintaining constant naval operations based on a misidentified biological sound.
- The military's institutional culture of extreme secrecy actually prevented the sound from being identified sooner, as it was never shared with independent scientists who possessed relevant expertise in marine biology.
- Magnus notes that confirmation bias affected the military such that they collected evidence supporting the submarine theory while ignoring contradictions, similar to how any authority-driven institution can develop self-reinforcing false explanations.
- Herring have been fished intensively by humans for millennia to found cities and build cultures, so their accidental role in creating a decade-long military crisis represented a moment when the hunted species had 'the power and upper hand' over their human pursuers.
Topics
Transcript
Hey, it's Lulu. This is Radiolab, and it's summer. In the past, there has been hot girl summer. There's been hot vac summer. This summer, arguably, is kind of turning into hot diarrhea summer, the one that no one wanted. But we here at Radiolab are offering you something different, which we are calling Cold War Summer, or I'm calling it that because we just realized this will be our third story that involves the Cold War in a month. This one is really special. We're bubbling it up from the archives. It's a tale of espionage. It's a real whodunit that involves submarines, periscopes, hydrophones, a bunker. And I didn't see the answer coming. Enough out of me. Let's…
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