Post # 9.Fish Farts!
!Indian Pond Sampling
There I was sitting alone at a boat landing on Indian Pond; a remote man-made reservoir at the headwaters of the Kennebec River just below Moosehead Lake.
It was just before dark on 18 May 2008. It was so quiet I kept looking around to see if a bear or a moose was sneaking up on me. Maybe bigfoot? Then out of nowhere I heard the unmistakable sound of a fish fart!
Listen to what I heard:
I was amazed! If you were there, you would have heard me talking out loud trying to explain to Bigfoot how it was impossible for a fish fart to be heard in a remote lake in Maine. That’s because at the time I thought that the only fish that made fart sounds, formally known as “fast repetitive ticks” or “FRTs”, were the Pacific and Atlantic herrings (Clupea harengus and C. pallasi). Two teams of scientists, one from Canada and the other from Europe, had independently described the herring sounds just a few years before (2003). The idea that fish might use fart sounds for communication quickly caught on with the media and general public with radio and tv interviews. The scientists even won an Ig Noble award from the journal “Annals of Improbable Research” in 2004.
FRT sounds start with a broadband pulse of sound like “kkkch” followed by a series of tic or tap sounds that continue for a while with each new tic farther and farther apart. Here are examples of FRTs I recorded in Maine, the second one is the one I first heard in Indian Pond.
Why did I think it was such a big deal to hear a fish fart sound in Indian Pond?
The problem was there were no herring anywhere near Indian Pond. In fact, there were no fish in the herring family at all in the lake. So how could I be hearing fish farts? Well I began to research the topic and found that the 2003 studies were not the first to describe this type of sound, but in fact, fish farts were among the first fish sounds to be reported in the scientific literature! As far back as 1857! They just were not called farts, but were referred to more “delicately” as air passage sounds. It turned out that fart sounds are just one of a wide range of sounds often called “air passage” or “pneumatic” sounds, and which I now term “air movement” sounds, because they involve air movement within a fish, or air passage from the anal vent, gills or mouth.
Needless to say, I was very excited by this discovery and Francis Juanes and I attempted to publish the findings many times. But our papers were rejected over and over because scientists just plain did not believe the fart sounds we reported were produced by fish, or if they did, they did not care because the prevailing wisdom was that these types of sounds are just incidental to physiological processes and therefore not important enough to study or publish. What they meant by “incidental” is that just like for us, when we burp or fart, its not a form of communication, but just a physical process. Hmm, maybe that’s not entirely true for kids!
Anyway, unless we could prove without doubt that the sounds were made by fish, and what the species were, we could not get our findings published. So, we set out to get the evidence we needed. Unfortunately, funding agencies were not interested in supporting our proposed research for similar reasons. At the time, there was simply not much interest in basic observational science, especially in freshwater habitats, and especially not for air movement sounds.
So, did we give up?
Of course not! We just went out and did it ourselves. Without funding, we had to work in our spare time and during trips of opportunity. It took ten years of hard work, but we did get our proof of air movement sounds in freshwater fishes throughout the region. We still don’t know what species produced the fart sound I heard in Indian Pond that day, but it was likely a trout or chub. In our follow-up work, we described the air movement sounds of five fishes, the alewife (present in the lower Kennebec River and other rivers, but not Indian Pond), brown trout, rainbow trout, brook trout, and the white sucker. We also described sounds that are most likely made by the Atlantic salmon. All these species occasionally produce FRT sounds, but more often produce other types of air movement sounds.
Rountree, R.A., F. Juanes, and M. Bolgan. 2018. Air movement sound production by alewife, white sucker, and four salmonid fishes suggests the phenomenon is widespread among freshwater fishes. PLoS ONE 13(9): e0204247. https://doi.org/10.1371/journal.pone.0204247
What are air movement sounds?
Many fishes have a gas bladder in their body that functions in one or more ways depending on the species. In some fish the gas bladder is used like a lung for respiration, in others it is used for buoyancy control, and in some fishes it is used for sound production (like the cusk-eels I talked about in an earlier post). In more primitive fishes, there is a connection between the gas bladder and the digestive tract because the only way the fish has to fill or empty the gas bladder is to gulp air at the surface or release air through the anus, gills or mouth. These more primitive fishes are called “physostomous” fishes, while more advanced fishes that do not have the gut connection are called “physoclistous” fishes. Physoclistous fishes with a gas bladder can fill and deflate it by directly moving gas in and out of the blood stream through a special structure called the Reta mirabilia. Note that physostomous fishes are among the most diverse and numerous fishes on earth (for example, many of the freshwater fishes kept in aquariums are physostomous).
Often when you see a fish jump, or splash at the surface, that’s when it is gulping air to fill its gas bladder. At this time, they sometimes makes sounds as the gas is moved internally or vented through the anus, mouth or gills.
The first time I ever observed this behavior was just after dark on 30 April 2008 in a tributary of the Connecticut river. I saw a small fish jump and then a moment later heard it squeak. Here is a slide showing the frequency structure of the sound series (top colored section). The circled areas show the sound of the fish jumping and then its squeak. The color indicates how loud the sound is and the y-axis indicates the frequency of the sound. Chanel 1 (very top) is the underwater sound, and channel 2 is the sound from my dubbing microphone where you can also hear the sound of the jump (but not the squeaks) and the sound of my voice as I made notes.
Listen to what I heard and how I reacted
I later documented this type of behavior in the alewife which I first heard in a tributary of the Kennebec River in Maine.
The alewife primarily makes sounds I call “coughs” as they expel air through their gills, but sometimes make a “pop” sound as an air bubble erupts from the mouth. They rarely make fart sounds but I have not yet been able to determine how (I’ve never seen air escape from the anal vent and suspect the sound is made by internal movements as Russian scientists have suggested for salmon).
Listen to the alewife “cough” sound
In the following video you can see several alewife (at half speed and amplified). One gulps air in a rapid burst to the surface in and then can be seen diving down from the upper right corner of the screen. If you watch closely you can see the bubbles released from the gills after each cough. A pop can be heard when it releases a large bubbles from its mouth at the end of the sequence.
Watch a video of river herring, alewife, sound production
Here is the sound that the white sucker makes after it gulps air at the surface. Unfortunately, I’ve never been able to capture it on video, but have observed it numerous times.
Listen to the white sucker’s sounds:
Finally, here is the sound made by a brown trout I recorded on Cape Cod. You will see one of the fish rise to the surface to gulp air in the upper right corner and then make sounds as it releases air from its gills.
Brown trout sound production
Based on our work, some of which is still to be published, we believe that air movement sounds are widespread among freshwater fishes (and probably marine fishes too). Although these types of sounds are likely incidental in many fishes, so few species have been studied that it’s premature to conclude that no fish use this type of sound for communication. In fact, there is already some circumstantial evidence that some fishes do use air movement sounds for communication. But even if not, we have shown that the sounds are unique to each species (so far studied), and therefore can be used in passive acoustic studies of those species. If you hear the alewife cough sound, for example, it pretty certain that at least one alewife is nearby. Thus, descriptions of this type of sound in fishes is very useful to scientists, resource managers, and conservationist, and is absolutely worthy of study and publication. We believe it is unfortunate that scientists have virtually ignored this behavior for so long and that we can learn a lot about fish by examining this behavior in other species.