Fishy Flatulence

Flatulence isn't a topic that's normally discussed in polite society, but for some fish, it can play an important social role and can even mean the difference between safety or becoming a predator's next meal.

Scientists have discovered that Atlantic and Pacific Herring deliberately release air from their vents to create high-frequency underwater sounds. But these noises are not a response to fear or feeding and are not due to gas produced in the gut. Instead, the fish use air gulped from the surface which is then stored in their swim bladders and expelled through a duct with an opening next to the anus.

The noise is then triggered by darkness and high fish densities, suggesting that the herring actively communicate by breaking wind in order to stay close together and form protective shoals at night. Most importantly, however, Herring can hear frequencies up to 40 kilohertz - well beyond the hearing range of most other fish. So this method of nighttime communication helps the herring to maintain contact after dark, but without giving their position away to predatory fish.

Perhaps most amusingly though, the high-pitched noise is always accompanied by a fine stream of bubbles...