Fish That Fart
The discovery that herring communicate using their own flatulence is one of marine biology's more unexpected findings. While fish lack the intestinal microbiome complexity that drives mammalian gas production, several species have evolved fascinating uses for gas — from deliberate acoustic signaling to buoyancy management. The ocean is, it turns out, slightly more flatulent than previously assumed.
The Herring Communication Discovery
In 2003, marine biologists Ben Wilson and Robert Batty from the Scottish Association for Marine Science, along with Lawrence Dill from Simon Fraser University, published a landmark study in the journal Proceedings of the Royal Society B. They discovered that Pacific and Atlantic herring produce rapid bursts of bubbles from their anal region, which they termed 'Fast Repetitive Ticks' or FRTs — an acronym whose selection was almost certainly deliberate. These sounds are produced by releasing gas from the swim bladder through the anal duct and are distinct from the herring's digestive gas. Crucially, FRT production increases in the presence of other herring and decreases when alone, strongly suggesting a social communication function. The researchers hypothesized that FRTs allow herring to maintain school cohesion in darkness, when visual signals are unavailable.
The Swim Bladder: A Multi-Purpose Organ
Most bony fish possess a swim bladder — a gas-filled internal organ used primarily for buoyancy control. The swim bladder allows fish to maintain neutral buoyancy at various depths without constant swimming effort, by adjusting the amount of gas it contains. In many species, the swim bladder also plays roles in sound production and detection. In herring specifically, the swim bladder is connected to both the inner ear and the anal duct, creating a remarkably integrated acoustic and buoyancy system. Gas released through the anal duct produces the distinctive FRT sounds; gas absorbed or secreted through the swim bladder wall adjusts buoyancy. This dual function in one organ system represents an elegant example of evolutionary economy.
Sharks, Manatees, and Other Gassy Creatures
Sharks lack a swim bladder and instead manage buoyancy partly through a large, oil-filled liver (squalene is less dense than water) and partly by swallowing air at the surface, which some species store in their stomachs temporarily. Some species have been observed releasing this stored air in ways that are functionally equivalent to burping or farting. Manatees, being mammals with functional intestinal tracts, produce substantial intestinal gas as a by-product of their fibrous, plant-based diet. Research on West Indian manatees has shown that they regulate their buoyancy in part by retaining or releasing intestinal gas — effectively using flatulence as a depth control mechanism. A manatee with digestive difficulties can become involuntarily more buoyant and have difficulty diving.
The Science and Legacy of the Herring FRT Study
The herring FRT study won the Ig Nobel Prize in Biology in 2004, awarded annually for research that 'makes people laugh, then think.' The Ig Nobel is sometimes dismissed as purely comedic, but the underlying research was peer-reviewed, methodologically sound, and published in a high-impact journal. It has subsequently been cited in over 150 academic papers on fish acoustics, underwater communication, and shoaling behavior. The FRT discovery also has practical implications for acoustic underwater monitoring: submarines and research vessels that rely on sonar have learned that large herring schools can produce detectable acoustic signatures, which historically led to false readings in naval operations. The Swedish Navy apparently investigated unexplained underwater sounds for years before the herring explanation emerged.
Did You Know?
- The herring FRT study won the 2004 Ig Nobel Prize in Biology — awarded for research that makes people laugh, then think.
- Manatees use intestinal gas retention and release as a partial buoyancy control mechanism.
- Herring FRT sounds are produced from the swim bladder via the anal duct, not from intestinal fermentation.
- The Swedish Navy spent years investigating mysterious underwater sounds later attributed to herring flatulence.
Fun Fact
The researchers who discovered herring FRTs named their acoustic phenomenon with the acronym deliberately. When asked about this in a follow-up interview, lead author Ben Wilson confirmed the naming was intentional and that it helped the paper get attention — a rare case of scientific flatulence pun advancing the field.
Sources
- Wilson, B. et al. (2004). Pacific and Atlantic herring produce burst pulse sounds. Proceedings of the Royal Society B: Biological Sciences, 271(Suppl 3), S95–S97.
- Dunning, D.J. et al. (1992). Alewives avoid the underwater sounds produced by a moving vessel. North American Journal of Fisheries Management, 12(4), 724–733.
- Reynolds, J.E. & Rommel, S.A. (1996). Structure and function of the gastrointestinal tract of the Florida manatee, Trichechus manatus latirostris. Anatomical Record, 245(3), 539–558.
- Popper, A.N. & Fay, R.R. (2011). Rethinking sound detection by fishes. Hearing Research, 273(1–2), 25–36.