Do Fish Fart? Yes, Herring Do It on Purpose, and a Bloated Bass Needs Help

Do fish fart? Yes. Herring do it on purpose, in the dark, in streams of tiny bubbles that tick like a fast clock, and the scientists who proved it won a prize. Most other fish burp instead. Below: who passes gas and how, whether sharks do, and what to do when a bass comes up from deep water swollen like a balloon.

In 2004 the Ig Nobel Prize in Biology went to the team that showed herring communicate by farting, shared with the Swedish scientists who traced mysterious “Soviet submarine” sounds in their waters to schools of herring.

The herring that talks with bubbles

Ben Wilson, Robert Batty and Lawrence Dill filmed Pacific and Atlantic herring in tanks at night. Each fish let out a fine stream of bubbles from its anal duct, and each stream made a sound. They named it the Fast Repetitive Tick, because that is what it sounds like. The pulses run from 1.7 to 22 kHz, so the top end is above what an adult can hear. A burst lasts 0.6 to 7.6 seconds.

Three details make it more than a joke. The herring did it mostly at night, more often when more herring were in the tank, and without any trip to the surface. Wilson’s team concluded the sound is probably social: a way for a school to keep together in the dark, when eyes are no use.

Herring can do this because of their plumbing. A duct connects the gut to the swim bladder, the gas-filled bag that keeps a fish from sinking. Gas travels from bladder to gut and out the back door. Most fish lack that route.

That plumbing also solved a Cold War mystery. Swedish scientists spent years chasing underwater sounds their navy took for foreign submarines. The sounds were herring. Both teams shared the 2004 Ig Nobel Prize in Biology (Nature News; Scottish Association for Marine Science).

Do other fish fart?

Not the way herring do. Most fish with a swim bladder get rid of extra gas by burping it out through the mouth or gills, as the Naked Scientists explain. A rising fish has to lose gas, because the gas in its bladder expands as the pressure drops. A herring can send it out either end. A bass has to burp.

Do sharks fart?

Sharks have no swim bladder, so there is no bladder gas to vent. One shark found a workaround. The sand tiger shark swims to the surface, gulps a mouthful of air and holds it in its stomach, the Aquarium of the Pacific reports. That pocket of air lets it hang almost motionless without sinking, handy for a slow hunter.

Do fish poop?

Yes, every one of them. Whatever a fish cannot digest leaves through the anus, often as a thin dark string that trails for a moment before it drops. Apart from the herring, no fish has been shown to make a sound at the back end.

The angler’s part: a bloated bass

It turns serious over deep water. A smallmouth bass hooked in 30 ft (9 m) and reeled straight up has no herring duct and no time to burp. The gas in its swim bladder expands as it rises. At the surface the fish lies on its side, belly swollen, and cannot swim down. That is barotrauma. The Arkansas Game and Fish Commission and North Dakota Game and Fish both put the danger zone at more than 20–30 ft (6–9 m).

Anglers have two fixes, and the numbers surprise people.

Fizzing means puncturing the swim bladder with a hollow needle to let the gas out. B.A.S.S. recommends going in through the side, with a 1.5 in (38 mm) 18-gauge needle, at the first sign of distress (Bassmaster 2023).

A descending device is a weighted clip or release rig that carries the fish back down to the depth it came from. The pressure at depth squeezes the bladder back to size and the fish swims off. No hole, no needle. Arkansas GFC and North Dakota Game and Fish call it the less invasive option.

The hard number comes from Madden and colleagues, who tracked 106 smallmouth bass in 2024. Of the fish fizzed with a needle, 57% could not control their buoyancy over 180 ft (55 m) of depth and sank, dying. Of the fish punctured a second way, 61% did the same. More often than not, the needle sent the fish to the bottom.

What to do with a bloated fish

1. Read the signs. The fish came from deeper than 20–30 ft (6–9 m), floats on its side, the belly is tight and round, and it cannot right itself. That is barotrauma, not exhaustion.
2. Work fast and wet. Keep the fish in the water, hold it with wet hands, skip the photo. The catch-and-release basics cover the handling.
3. Reach for the descending device first. Clip it to the lower jaw, lower the fish to the depth you caught it, release. Arkansas and North Dakota fisheries staff prefer it because nothing gets punctured.
4. Fizz only if you must keep the fish, and only the B.A.S.S. way. In a tournament livewell, use a 1.5 in (38 mm) 18-gauge needle through the side at the first sign of floating, never as a routine (Bassmaster 2023).
5. Know the odds before you pick up the needle. In Madden’s 2024 study, 57% of fizzed and 61% of punctured smallmouth sank instead of swimming off.
6. Stop making bloated fish. If every fish from a deep school comes up swollen and you are releasing them, move shallower or send each one straight back down.

A herring farts to keep its friends close in the dark. A bass cannot fart at all, which is exactly why it needs you when it comes up from deep water. More odd questions, from whether fish sleep to whether they feel pain, get the same sourced answers in the fish facts collection.