They were mystified by an underwater sound made by the fish, then realised it was the creatures breaking wind.
They thought the fish were doing it because they were scared. They put shark scent in the water - but it made no difference.
Then they found out there were more farts when more fish were in the tank and when it was dark, indicating that they were using them to communicate.
The scientists also discovered that - unlike a human fart - the herring version was not caused by what the fish had eaten.
Raspberry
This was because the number of farts did not increase after the herrings had been fed.
The scientists have compared the sound the fish make to "a high-pitched raspberry".
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