Wait, fish make noise? Meet the ‘fish listeners.’ (audio)

We know this question has been keeping so many of you up at night: What does a cusk eel chorus sound like?

We often think of the ocean as a silent world, completely separate from our own. But it’s not so silent, and we’re not so separate. The ocean is quite noisy, and we’re making it even noisier, which has major ramifications that we’re just beginning to understand.

So yes, fish make sounds, and we have the audio to prove it.

Marine ecologist Leila Hatch and fellow fish listener Rodney Rountree – aka “Captain Kirk of the fish world” – serve as guides to the soundscape of the sea. Listen to the full audio story above. 

Note: This audio story was designed to be heard. We strongly encourage you to experience it with your ears, but we understand that is not an option for everybody. For those who are unable to listen, we have provided a transcript of the story below. (If you’re reading this off our website and don't see an audio player, click here to access the audio player.)

Transcript:

EVA BOTKIN-KOWACKI: What sounds do cods (cod?) make? Cods? Cod? 

LEILA HATCH: Cod. Cod make a mm mm mm mm mmm. 

[Rhythmic cod grunting] 

LEILA: I’m not as good at grunting. 

EVA: That’s Dr. Leila Hatch. She studies the sounds of the ocean.

LEILA: And then haddock make a thumping, a repeated thumping that’s really: thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump, thump and it can get louder. 

[Loud, fast haddock thumping] 

LEILA: And often you’re not really listening to one individual, you’re listening to a chorus of individuals.

[Pensive music]

EVA: I’m Monitor science reporter Eva Botkin-Kowacki. 

We often think of the ocean as a whole other world, silent and completely separate from our own. But it’s not so silent. And we’re not so separate. The ocean is quite noisy, and we’re making it even noisier, which has major implications that we’re just beginning to understand.

LEILA: When I talk to people about the noise we introduce in the ocean, the first thing I do is ask them to close their eyes. Because I don’t think people can be fully present for their ears without shutting down our most dominant sensory input. But the moment that we do, we start to really pay attention to just how much we rely on our hearing. And I think that’s when you start to have some empathy for what the experience is of losing that. 

[Upbeat music]

RODNEY ROUNTREE: I kind of think of myself as Captain Kirk of the fish world, you know. So you’re out going where no one’s ever gone before and dropping a hydrophone in. 

EVA: That’s Dr. Rodney Rountree. He calls himself “The Fish Listener,” because he’s on a decades-long quest to record and identify the many unknown sounds that fish make.

RODNEY: Much to my wife’s dismay, pretty much every vacation, I lug a hydrophone along and drop it in the water.

EVA: A hydrophone, by the way, is an underwater microphone.

My producer and I met Rodney on the town dock in Cotuit, Massachusetts on Cape Cod one July evening. We were hoping to experience the thrill of listening to a chorus of fish. 

Rodney showed up in a Hawaiian shirt that had a tropical fish design. He told us it was one of about 25 his mom had made for him before she died. He was all business at first. He dropped a hydrophone in the water, hooked it up to his laptop, a recorder, and two sets of headphones.

[Ambient dock sounds]

RODNEY: Wires and cables are the bane of my existence.

EVA: He also filled a small plastic kiddie pool with seawater, cast two fishing lines, and tossed traps into the water. Then the three of us settled into camping chairs, put on the headphones, and waited for something to happen.

[Time-passing music]

EVA: If I stuck my head in there, would I be able to hear the fish?

RODNEY: Some of them you would. In fact, [laughs] I was demonstrating this to some students at Rutgers some years ago, and I was on a floating dock and some students all came out. And one guy was so excited, he was like, really, can I...? Can I...? And so he immediately dunks his head underwater [laughs] and starts trying to listen. And then of course he had to make sounds, too. So I recorded it. Sometimes you can hear fish if you listen, like the toadfish and the cusk eels. A lot of times you don’t hear them ’cause you’re just too busy, you’re too active and the sounds are muffled. 

EVA: Sitting on the dock with Rodney, I was able to hear the underwater world unmuffled. It almost sounded like I had stepped onto another planet.

[Ambient underwater noise from the hydrophone, dripping sounds]

EVA: We were listening for one fish in particular: cusk eels. They get their name from their long, eel-like bodies. The males make a distinctive mating call right around sunset to attract females. And a bunch of them together makes quite the chorus underwater. Actually, 20 years ago, Rodney discovered that cusk eels live on Cape Cod by dropping a hydrophone in the water at the very same dock we sat on. But the night we met Rodney, the cusk eels were mysteriously quiet. 

RODNEY: Okay, Mr. Cusk Eel. You’re not going to show me up, are you? 

EVA: As the hours ticked by, the sun set, the street lights nearby clicked on, and the stars started to come out. A steady dripping sound came from the hydrophone, which Rodney said probably meant his kiddie pool had a leak. But no cusk eels. I did hear another fish sound, though…

[Fish sound like an old creaking door]

RODNEY: Woo! That was a fart.

EVA: It sounded very creaky. 

EVA: Fish make sounds in a variety of ways. Sometimes they twitch muscles near their swim bladders or rub body parts together. But some scientists – Rodney included – say that they also might fart intentionally to communicate. That’s a controversial idea. In fact, when Rodney first heard freshwater fish make a farting noise, other scientists didn’t believe him and he couldn’t get a paper published or funding to do more research. It took him 10 years to prove that freshwater fish do make farting sounds. He and a colleague finally published a paper last year. 

EVA: Why is it important to listen to fish?

RODNEY: I've told people for years now the analogy... if you could imagine a bird biologist who has never listened to the bird sounds. They know the birds are making sounds but they never think, “Oh I could listen to the bird and understand more about its behavior. And I can listen and I can count birds and I could find out something about where they are and what they’re doing.” That’s where we are in the fish world. So people kind of knew fish made sounds, but they weren’t really taking advantage of it the way that bird people, or even frog people do.

EVA: Why should we care about those sounds? 

RODNEY: Well, why should we care about bird sounds? Why should we care about whale sounds? I mean it’s part of understanding the world that we live in. It’s part of understanding how to safeguard that world, how to be good stewards of the world.

EVA: And sound also really matters to fish... 

LEILA: The more we study them, the more we know that definitely hearing is a rule, that the vast majority of fish are using acoustic detection as part of sensing of their environment, that it’s critical. And then that it’s often the rule, not, you know, not at the same level, but it’s often the rule that they make sounds. 

EVA: Some fish use sounds for communication, navigating their environment, attracting a mate, or scaring off predators. So sound is pretty important in a fish’s life. And sound travels more than four times as fast underwater.

LEILA: And it also can go much greater distances particularly at low frequencies without what’s called attenuating, or losing its energy.

EVA: That means that sound travels really efficiently through water. So in deep ocean conditions, some noises can travel over hundreds of thousands of miles. 

EVA: Fish don’t have ears, do they?

RODNEY: Oh, sure they do. They don’t have external ears, but they have internal ears that are very much like our ears. Though, I have to put a caveat. When you say fish, basically you’re talking about a huge diversity of animals and in many ways scientifically we are fish. We’re just a small little branch of fish. We just happen to not live in water. 

EVA: Rodney’s talking about how all animals with a spine evolved from fish – humans included. Whether intentionally or not, humans tend to see themselves as the center of the universe. But clearly for Rodney, fish are also pretty important. He talks about them like they’re people. Even when he catches them on a line or in a trap.

[Rodney casts a fishing line, plop!]

EVA: Catching fish is actually part of how he does his research. Dropping a hydrophone in the water is a passive approach. But when he catches a sea creature, he’ll put it in his kiddie pool and gently nudge it to see if it will make a noise. He calls this technique, “auditioning.”

RODNEY: [trickling water in background] Okay, Mr. Spider Crab. [muffled scraping sounds] Just the scraping sounds. You going to scream for me? Nope. No sounds from Mr. Spider Crab. 

EVA: Do they scream? 

RODNEY: I don’t know.

[Laughter]

EVA: Scientists actually don’t know a lot about the ocean. It’s one of the least-explored parts of our world. And fish sounds? They’ve only just begun to identify them. 

LEILA: There are some absolutely fabulous sounds, some of which we keep in folders as marine acousticians and are still of unknown origin. And what I like to always think about is the fact that those folders in some form have existed since the 1950s and people have now added names and known critters to some of them, and others of them continue to be that, “You know that ‘boing’ thing that sometimes you hear in the Pacific,” right? So for example there is something that people have called the Star Wars sound that it sounds like a really, really large rubber band being flung across a room [woop woop woop] and that is now attributed to Minke whales in the western Pacific. 

LEILA: For decades in very early Navy recordings they were absolutely positive that their underwater listening equipment was malfunctioning because they had such incredibly steady rhythmic sound at very, very low frequencies, below what humans can typically hear, that seemed to be a repeated woooo woooo woooo. [Leila imitates sound, fades into real blue whale sound] It was so rhythmic that it was understandable that they thought it was equipment. It was a blue whale.

EVA: Wow. Wow. You’re quite good at making those whale sounds. Is that part of the job description?

LEILA: That’s part of the job description [laughter]. One of the things we often have to do with sounds that are below human ability to hear is speed them up. So when you... and you know this, maybe, as a kid… kids of today would perhaps not know this because you can’t play your records faster in the same way as we used to be able to when I was a little kid and you could actually play with 45s and things like that. But if you did that, you know, then you get the Chipmunks, right? 

[Alvin and the Chipmunks singing in squeaky voices]

LEILA: The way they made those really early recordings of Alvin and the Chipmunks, which is to take people singing and speed it up and you get very chipmunk-y voices.

[Alvin and the Chipmunks slowed down, singing in regular voices]

[Alvin and the Chipmunks as broadcast, singing in squeaky voices]

LEILA: So anyway, if anyone ever plays you a blue whale or a fin whale call, you’ll know that you’re hearing it sped up in order to be able to hear it. 

EVA: Wow. I didn’t know that. 

LEILA: Yeah. If I’m mimicking what you would hear if we played it for you, it would be ooooh ooooh [Leila imitates], but that means in the world’s ocean, there’s oooooh oooooh [Leila’s voice is gravely]. You know, really long spaces between them. And all of that is so that a sound can go out there, bounce off of something, and be heard again. And like a lighthouse, it has to be at very, very even intervals. 

EVA: Whales and dolphins have captured people’s fascination. They’re often the stars of nature documentaries and crop up in pop culture, like in the movie “Finding Nemo.” 

[“Finding Nemo” clip. Dory imitates whale sounds: Wooooooooaaaaaaahhhh. Marlin: Dory. Dory this is not whale. You’re speaking like upset stomach. Dory: Maybe I should try humpback.]

EVA: People’s fascination with whales has led to more curiosity about ocean sounds – and that, in turn, led us to wonder: Do human sounds affect ocean animals?

[Wonder music]

Researchers have already found that human sounds can seriously affect fish. On the most extreme end, explosive sounds, like from oil and gas exploration, [boom!] can reverberate through the water and cause a fish’s swim bladder to burst, killing it. [boom!] Loud noises can also damage fish eardrums, just as listening to music too loudly can injure ours. And sometimes human noise just makes it too loud for creatures to use sound to communicate.

LEILA: So it’s the phenomenon of you arriving early at a cocktail party and you come with a friend and there’s not very many people in the room, and you talk to each other casually, share information [quiet crowd noises behind Leila]. And then the room starts to fill up as people arrive at the party [crowd sounds get louder]. And now you either have to step closer to one another to talk at the same level, or you have to talk louder, or you have to make modifications or you’re going to lose part of that information exchange. That’s called being masked by background noise.

EVA: And for those chorusing male cusk eels, that might mean they can’t find a mate, which could have tragic consequences for the species. But could the fish just get louder?

RODNEY: Most of the time, I don’t see that. I see the fish... because a lot of these sounds are the advertisement sounds. So the fish is already calling as loud as it can because it’s competing with all the other males for that female. So it doesn’t have a lot of scope to call louder.

EVA: When a boat went by the Cotuit town dock, the sound coming through the hydrophone was so loud compared to everything else underwater that I had to rip the headphones off to protect my ears. 

Here’s what the boat sounded like above water:

[Speed boat sounds above water, voices of some people on the boat chatting over a low hum]

EVA: And the same few seconds below the surface:

[Speed boat sounds below water, grating sound like ice in a blender]

EVA: Those little speed boats are just a small part of human noise in the ocean. Oil drilling, construction, military sonar, and ship engines create a ton of noise. And, by the way, over 90% of the world’s trade is moved by sea. That’s a lot of massive ships, and they’re a lot noisier than the small boats at the Cotuit town dock. 

LEILA: You know, we typically don’t think about where things come from. We definitely don’t think about, you know, sound as being introduced into the ocean as part of getting a T-shirt, right? But it’s part of getting a T-shirt, or a car, or a washing machine that’s come from overseas. 

EVA: So can anything be done about noise pollution in the ocean? 

LEILA: The good thing about noise as a pollutant is when you turn it off it goes away. 

EVA: There’s another reason to shop local. 

Ship engines can also be made quieter. In fact, as Leila told me, boat builders already mute the noise they make above water. But underwater, that’s not the case. So some scientists are advocating for regulations mandating quieter engines.

[Trickling water]

EVA: Back on the Cotuit dock, boaters had all gone home and it was quiet. Four hours had passed, and yet still we waited.

[Trickling water]

EVA: I’m straining to hear.

RODNEY: It's 9:30. They should be calling. I mean literally I was here a few days ago and at 9:30, I mean, they weren’t calling a lot, but they were calling. 

EVA: They were noisy? 

RODNEY: I mean they should have chorused already.

EVA: Rodney wasn’t quite sure what was happening with the cusk eels. He did say the chorus had been quieter in recent years. He didn’t think boats had scared them off. But it might have been another human influence. Fertilizer and septic tank run-off might make the water less habitable for cusk eels, and the population might be dwindling. 

RODNEY: Very disappointing, you don’t get to hear at least one cusk eel. 

EVA: I heard a little distant honk again.

RODNEY: Oh did ya?

EVA: I keep leaning over the water like it’s going to help me hear it more. 

[Rodney chuckles]

EVA: In the end, we didn’t hear the cusk eel chorus that night. We did hear several other fish sounds, though. There was the fish fart. [Squeaky fart noise] A clucking sea robin. [Sea robin clucks] Several toadfish honks. [Medley of toadfish honks] Something that might have been a distant toadfish growl. [Toadfish growl] And a noise Rodney couldn’t identify that sounded a bit like Donald Duck. [Unknown fish sound].

But the cuskeels didn’t show. 

EVA: Can you imitate it? 

RODNEY: Well, a cusk eels itself sounds like, heheheheheh heh heh. And then just imagine like just a hundred fish doing that. It’s pretty loud. 

EVA: Rodney told me later that his hydrophone did pick up one cusk eel calling for a mate, but it happened during a brief moment when neither of us had our headphones on. He sent me the recording:

[Single cusk eel calling for a mate, sounds a bit like a woodpecker pecking]

EVA: Rodney also sent me a recording of the cusk eel chorus from a noisier night. And let me just warn you, it’s not exactly what you might expect of a “chorus.” Still, there is something hauntingly beautiful about it. 

[Cusk eel chorus, sounds a bit like cicadas]

Credits:

EVA: Thanks for listening. This story was part five of “Peering into the deep,” a five-part series exploring our evolving understanding of life beneath the waves. To check out the rest of the series, go to csmonitor.com/Peeringintothedeep. 

This audio story was reported by me, Eva Botkin-Kowacki. My producer was Rebecca Asoulin. Editing by Samantha Laine Perfas and Noelle Swan. Sound design and engineering by Noel Flatt and Jeff Turton. Special thanks to Em Okrepkie and Erin McNeill. Fish sounds are courtesy of Dr. Rodney Rountree and the National Oceanic and Atmospheric Administration.

This story was produced by The Christian Science Monitor, copyright 2019.