The Submarines That Were Herring
For years, the Swedish Navy hunted foreign submarines by their sounds in the dark water. Some of the sounds turned out to be fish.
What was reported
In the 1980s and 1990s, Sweden believed foreign submarines were secretly entering its waters. In 1982, the navy spent weeks hunting a suspected intruder in Hårsfjärden, near a naval base south of Stockholm, and over the following years its hydrophones picked up many strange underwater sounds, including bursts of high-pitched ticking, which were taken as signs of submarine activity.
Military sound experts couldn't identify all of them. The submarine hunts became a matter of national tension and a source of diplomatic rows.
Explanations offered
In the 1990s, researchers studying the recordings found that some ticking sounds matched shoals of herring. In 2003 they published evidence that herring make a fast series of ticks by releasing gas bubbles from their rear ends, probably to communicate at night. Not every incident was herring, and whether real submarines were present in some cases is still debated.
- When
- 1980s–1990s; explained in 2003
- Where
- Stockholm archipelago, Sweden
- Witnesses
- The Swedish Navy, then marine biologists
- Status
- Partly explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.
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