Speaking with the fishes
CODCAST E2 Speaking with the fishes
SPEAKERS
Rodney Rountree, The Silent World narrator, John Last, Amalis Reira, Eric Parmentier
John Last 00:04
In the opening of Jacques cousteau's most famous documentary film, a team of scuba divers lights flares and descends into the bubbling deeps as they go, the sound behind them fades slowly into nothing you. Cousteau's documentary and the book that accompanied it defined so much about how we imagine the deep sea today.
The Silent World narrator 00:31
This is a motion picture studio 165 feet under the sea. To make this film, they roamed in a mysterious realm, the silent world.
Rodney Rountree 00:46
I was just looking I've got a couple copy of cousteau's book, silent world, right? But even because still knew that the world wasn't silent, he knew about whale sounds stuff. Still, the perception is that it's quiet and we just don't listen.
John Last 01:05
I'm John Last and this is the codcast, and as you may remember from last time, this is a story about the quest to understand a totally new sound. This little grunt is the sound made by an Arctic cod. And until very recently, we had no idea that it could even make it. But the Arctic cod isn't alone. Hundreds of fish are known to make sounds far be it for me to contradict the esteemed Jacques Cousteau, but it turns out that the silent world is a pretty chatty place. Today, we're going to look at some of those sounds that Cousteau didn't talk about. How fish make their strange little noises, and how we can even begin to understand why. And we're going to start with the man you just heard from. No Not Jacques Cousteau, Dr Rodney Rountree, aka the Fish Listener.
Rodney Rountree 02:02
Some people ask me why Fish Listener not Fish Whisperer, because they like that. It's because I don't talk to the fish. I listen to the fish, and so I like to be considered a good listener, at least with fishes.
John Last 02:23
Rowntree is one of the world's leading experts in fish sounds. Over time, he's collected an enormous library of the sounds they make, from the sharp snap of the Acipenser oxyrinchus to the rough scads crackling grunt. That's Rodney you can faintly hear there getting excited in the background. Rodney got his start when one day he, almost by accident, recorded the spawning calls of the cusk eel, a small, thin fish common on the Eastern Seaboard. Here he is telling the story in a 2016 video.
Rodney Rountree 02:58
It comes out at sunset, the males start calling and chorusing like frogs to try to attract the females, but this is the sound the male makes trying to attract a female... and that sound until I recorded it with Jeanette Bowers Allman in the late 1980s had been recorded by scientists up and down the East Coast, but it had always been either an unknown or mistaken for another fish.
John Last 03:37
Six years later, and Rodney is still probing the unknown.
Rodney Rountree 03:41
Yeah, I mean, that's one of the things I often talk about, is that one of the things that draws me to this is the thrill of discovery, right? I've heard things that no one else has ever heard before. I've recorded and no one else has ever done this before, and I've said for years that, you know, you could go almost any place and drop a hydrophone in the water and hear things that we don't know what it is. You know, docs inNew York City, arguably the industrial heart of the world, you can drop a hydrophone off the side and hear things that we don't know what it is. That is just mind boggling to me.
John Last 04:23
Rodney's story points to something else we mentioned in our first episode, just how hard it is to get recordings of fish making their noises, even after decades of work gathering sounds from seascapes across the world, Rodney's recordings represent just a tiny fraction of the noises we know are out there.
Rodney Rountree 04:41
We know of the 30,000 or so fish species. We've only actually looked at a few percentage of those for sound production, but that is accelerating in the last couple decades, and we're looking at more and more fish. But this still is a drop in a bucket.
John Last 05:00
But the good news is, scientists have found a shortcut.
Eric Parmentier 05:06
My name is Eric Parmentier,
John Last 05:08
an ocean away from Rodney in a bright office in Belgium, is Eric parmantier. He's another fish sounds expert this time at the University of Liege for the past few months, he's been helping the team studying Arctic cod by cutting them up. As Eric explains, fish require a lot of physical adaptation to make a sound, which means whether or not they can make a sound is often clear once you open them up. In catfish, for example, you find tiny teeth that they grind to make their sounds, a process scientists call stridulation.
Eric Parmentier 05:47
It's not a nice sound. I mean, it is not really pleasant to hear that kind of sounds
John Last 05:52
Other fish, like the croaking gourami pluck a tendon in their fins,
Eric Parmentier 05:56
like a string, guitar.
John Last 06:01
They're not the only species with a musical band. Rodney's cusk eel makes its characteristic noise by turning its swim bladder into a tiny drum and beating it as much as 200 times a second.
Eric Parmentier 06:15
So it's quite fast. It means also that the fish need a lot of attention at the level of the physiology and infrastructure of the muscles.
John Last 06:27
In other words, to do any of this, fish need to develop highly specific body parts, ones that are clearly visible when dissected. But the good news is that means simply cutting a fish open can sometimes be the key to discovering a whole new means of communication. Don't believe me, consider the tale of the common herring. Farts.
Eric Parmentier 06:46
Ah, yes, I didn't speak about the mechanism at the beginning. So the scientists see that there were some bubbles coming from the from the anus and the first expected that the bubble was farting so that it was directly related to the food of the fish. So what they tried to do is to place different specimens in different tanks, giving them different food, expecting that if there is different food, they will have different farts, but it does not change anything.
John Last 07:30
Eventually, these scientists decided to cut these herring up, and what they found was that they had a unique connection between their swim bladder and their butt.
Eric Parmentier 07:39
The bubble is not the result of a digestive process, but is just an expelling of the air from the from the swim bladder.
John Last 07:49
Now, scientists believe this kind of farting could be used for self defense or even as a form of communication between individual fish,
Eric Parmentier 07:57
and they can use the bubbles to maybe to make schools when they are dispersed by the predator. And also, you can imagine that all these bubbles coming from the anus can be a nice defense systems. Just imagine you have 100,000 of a herring swimming together. You have a predator like like a shark or a dolphin, if all the fish make the bubble at the same time, so you have a screen of bubbles, and it gives the opportunity to the to the fish, to escape.
John Last 08:38
All this goes to show just how revealing it can be to cut a fish open and look at its guts. That's why, when it came time to explore the origins of this never before recorded Arctic cod grunt, Eric's expertise was a must. In the spring, the team studying the noises of Arctic cod put Eric on a plane and flew him to a research facility in the United States where tanks of fresh caught Arctic cod awaited him, and his scalpel. Amelie Riera was waiting too. She's the researcher we heard from last time, the first to record the sound of the Arctic cod.
Amalis Reira 09:14
We did some dissections. We looked at the insides of the fish to look at the sound producing apparatus, and we found the sonic muscles
John Last 09:26
Already Amalis and her team had a better idea of how the Arctic cod make their sounds with drumming muscles acting on their swim bladders, similar to other gadids like walleye pollock. But that's only the start of the questions that can be answered with good dissection work. One big question is, when do these mussels appear in the fish, and what it can teach us about the life cycle of Arctic cod.
Amalis Reira 09:48
For some species of fish, the sonic mussels are there year round, all the time. But for some others, the sonic mussels are only well developed during, say, the spawning season, which is when they might produce a lot of sounds, and then during the rest of the year, they kind of disappear or become really weak. So we are also going to be looking at, at what age, when is the first time that the Arctic cod develops Sonic muscles? It's like, you know, teenagers, like when the voice changes or something,
John Last 10:19
All those thoughts point to the big unanswered question still looming behind all this research. Dissections like Eric's help us understand how fish make their noises. But what can we say about why? Rountree says that, like many animals, the reasons for their communication tend to fall into a couple broad categories.
Rodney Rountree 10:44
There's like territorial sounds,
John Last 10:46
one fish sees another arrive and doesn't like the look of them, just like a dog, a cod might bark to warn off a rival or warn others of a predator.
Rodney Rountree 10:55
There's sounds that are made for courtship,
John Last 10:58
like birds, fish might also make their sounds to prove they're an attractive mate or draw the attention of females swimming nearby, these noises can be a clue to whether fish are spawning, like the sound of cusk eels Rodney first recorded,
Rodney Rountree 11:11
once you've attracted the female, you're now close. You don't have to be so loud. And so a lot of the sounds that we're talking about they're quiet sounds because they're meant for direct interaction between individuals, and what happens if you make a loud sound, you're exposing yourself to predators. So there's a lot of reason to be quiet, thinking sound is dangerous,
John Last 11:40
but often it's not so easy to separate sounds into categories. Fish might make just one sound or a variety of sounds. They might use the same sound in every situation or change it up each time. Here's Eric again,
Eric Parmentier 11:53
for example, in the damselfish, the industrial species, we have seen that we have sounds for courtship, sounds for territory defense. But the songs that are made during the territory defense are not the same. We have another kind of song that is made during fighting, and we have also another kind of song that is produced during what we call the mating the mating visiting. So the mating visiting, it is through after courtship, when the female come to the nest to lay, to lay the eggs.
John Last 12:31
That's a lot of sounds to study. If fish were speaking a language, it's a big vocabulary to unravel, but that's part of the problem facing scientists today, it's not always easy to understand what a fish means when it's speaking.
Rodney Rountree 12:46
It's been done for some things, but it's very difficult to prove that this fish making this sound is for this reason
John Last 12:53
in the lab, things can be a little easier.
Eric Parmentier 12:55
You place a male in an aquarium during 24 hours, and then you can add simply, you can simply add a female and the fish can try to make songs to attract them. Or you can place another male. And in this case, you will have another kind of songs. The songs that will be made are just there a defense of the of the territory. Sometimes, you saw fish. You can even get sound by simply by, uh, by placing in the in the tank a mirror.
John Last 13:27
but in the real world, it's not always so easy.
Rodney Rountree 13:30
Whereas the normal layman looking at it might go, yeah, fish barked, and all the other fish ran away. Well, yeah, but did they run away because they barked? And did he run away? Or someone because they saw the predator, or they smelled the predator? You know, it's so it's not easy, even if you have video and you're and single hydrophone and you're recording a sound, you hear a sound and you see a fish. Did that fish make the sound? Or did a fish behind the camera make a sound, or fish somewhere else make a sound.
John Last 14:09
Recently, technological advances have made this all a lot easier. Hydrophone arrays like one recently developed by Xavier Mouy helped triangulate the exact location of a sound, which combined with video, make it possible to pinpoint the exact fish that produced it. That helps clarify the reason why they made the sound in the first place, and knowing the reason is half the point. When fish make sounds, they're communicating something about their lives and their environment, something that may be of great use to us up on land. Knowing a species sound, Eric says, helps us know whether their populations are healthy, and could give us clues to managing the use of the water around times like spawning seasons, where they may be more vulnerable. Knowing lots of sounds helps us determine who's living in the society under the sea and how they relate to each other and compete for space.
Eric Parmentier 15:02
We know, for example, that sounds are species specific. So it means that if you have different kinds of sounds, you have different kinds of species. So it can help you to have an information about the biodiversity.
John Last 15:16
In other words, a cacophonous ocean may be in some ways a sign of a healthy one, or at least it should be. The truth is, the tiny grunts and chirps of fish are only one of many sounds in the ocean, and increasingly, they're being drowned out by noises like this. [engine sound]. Human noise is an increasingly large presence under the water, and next time on the Codcast, we'll be looking at how that transforms the world of fish and makes it that much harder to listen to what they're telling us for now, though, it's time to say goodbye. I'm John Last and this is the Codcast. See you next time. The codcast is produced with the support of the North Pacific Research Board. Music was provided by Blue Dot sessions. Our opener came from Jacques cousteau's 1956 documentary, The silent world sounds of the cusk eel, Acipenser oxyrinchus, rough scad and catfish come from Rodney Roiuntree's personal library of fish sounds. You can find more recordings on his website, fishecology.org, the croaking garami is from Beat up Peterson on YouTube, our damselfish recording and sounds of boats underwater come from the University of Rhode Island Sound in the sea project the Arctic cod, of course, was recorded by Amalis. I produce this podcast. If you like it, tell your friends. You can read more about this project at the North Pacific Research Board website, www.nprb.org.
