Don: Today on "A Moment of Science," herring make sounds when passing gas...

 

Yaël: Don, be serious!

 

D: I am serious, Yaël! The Atlantic herring is one of the most abundant fish on Earth!The silvery foot-long fish live in huge schools of thousands to hundreds of thousands of individuals.

 

Fishermen have long known that herring schools can release large clouds of bubbles that are visible from the surface. The bubbles are released through the anal opening, connected to the fish's swim bladder.

 

Y: What's a swim bladder?

 

D: It's a special, gas-filled organ that helps regulate buoyancy. Herring gulp air at the surface and store it in their swim bladders. It's also long been known that herring make chirp-like sounds, especially when startled or in danger, but biologists didn't know how these chirps were produced.

 

Y: I think I know where this is heading!

 

D: Yep! A pair of Danish biologists recorded herring housed in special pressurized tanks 

that replicated conditions at the ocean depths where herring are found. They discovered that the chirping sounds were actually produced by air release from the  swim bladder during the bubble production -- the first report of sound production by gas release in fishes.

 

Y: So the chirps are just a by-product of passing gas?

 

D: That is what's intriguing scientists, since the bubbles are released by the fish in response to stress, and occur whether the fish are ascending or descending, they don't think that it's simply part of controlling buoyancy.

 

Some scientists speculate that the sound and bubbles might work as a visual and  acoustic screen to confuse predators, but more studies are needed to determine if the  chirping bubbles have a behavioral function or not.