Fish Make More Noise Than You Think

IRA FLATOW: This is Science Friday. I’m Ira Flatow. For the rest of the hour– something fishy. One of undersea explorer Jacques Cousteau’s whose most famous documentaries was called The Silent World, but it turns out that below the waves it’s a surprisingly noisy place. And I don’t mean just whale sounds and dolphin clicks.

In research published in the journal Icthyology and Herpetology, researchers report that as many as 2/3 of the fish families within the ray-finned fishes either are known to make sounds or at least have the physical ability to do so. Joining me is Aaron Rice, principal ecologist in the K. Lisa Yang Center for Conservation Bioacoustics at the famous Cornell Lab of Ornithology in Ithaca. Welcome to Science Friday.

AARON RICE: Thank you so much for having me.

IRA FLATOW: How nice to have you. OK, first, which fish are we talking about here?

AARON RICE: So this group, the ray-finned fishes, the technical name being the actinopterygian fishes, pretty much encompass everything you think of as a fishy sort of fish. These are the salmon. These are goldfish. These are angelfish and butterflyfish and cichlids– pretty much everything that, when you think of a fish, that comes to mind.

There are three groups of vertebrates known by the term “fishes.” You have the cartilaginous fishes, the sharks, skates, and rays; the actinopterygians, these ray-finned fishes here; and then the lobed-fin fishes, which include coelacanth, lungfish, and tetrapods.

IRA FLATOW: And you found, what? The vast majority of them can make sounds?

AARON RICE: Yeah, so what’s been exciting watching this field develop over the past 10, 15, 20 years is that, historically, the idea of fish using sounds to communicate had sort of been seen as this oddity, that we knew there were a handful of species that were really good at it, and they seemed to be the exception rather than the rule. And one of the things that my colleagues and I started doing was piecing this together and say, wait we’ve got a species over here that does it, and there’s another species over here that does it. And we stepped back and looked at this giant pattern and found out, well, no, these aren’t oddballs, and these may not be the exceptions. They actually may be the rule as to how many fish are communicating.

IRA FLATOW: And they’re communicating, of course, to talk to one another.

AARON RICE: Exactly. And so like all other vertebrates, we see acoustic communication occurring in two different behavioral contexts. We have sort of reproductive context, where fish are trying to find a mate. You may have males advertising for females, trying to solicit them to lay eggs in a nest. And then you also have agonistic displays, where fish may be doing some sort of aggressive vocalization over food or territory, or a anti-predator warning.

IRA FLATOW: So how do you go from sound to communication? I mean, I might snore or sneeze, and that makes a sound, but it’s not communicating anything except I’m sneezing.

AARON RICE: Great question. So one of the things that we see is that we have a handful of species that have been really well studied for decades. And what we know is that if we do playback sounds of male vocalizations, it immediately will attract the female. And there’s been a number of cases where the role of sounds in mating behavior is both necessary and sufficient to produce a response from the females. And so where we have good examples in hundreds of different species, we can then begin to make this extrapolation.

But one of the things, too, in terms of your comment about snoring, which isn’t necessarily the same as you talking, the other component, though, is that for many fish that are producing non-volitional sounds– sort of not intentionally, but the byproduct of another behavior such as feeding or swimming– that still does communicate some information to eavesdropping species. So if you’re snoring and we hear it, we know that you’re asleep, and there is some communication. And so the idea is that any sort of sounds produced by animals may have a communicative function.

Now, that’s sort of– those non-intentional sounds are outside the scope of our paper. What we really wanted to focus on was those species and families that are making sounds intentionally.

IRA FLATOW: You know, when we make sounds intentionally, like speaking, we have vocal cords. How are the fish making these sounds?

AARON RICE: This is one of the things that’s so wonderful about studying a diverse group like fish, where, in contrast to the human larynx, which is the dominant source for humans communicating, fish produce sounds with all different parts of their bodies. So the most common acoustic mechanism is highly specialized muscles associated with a swim bladder in sort of the fish’s thoracic cavity. So we know that the swim bladder is primarily used for buoyancy. But in many species, there are really, really well-developed muscles that connect to the swim bladder, and the swim bladder essentially is serving as an amplifier to help radiate those sounds.

We have other species of fish that are grinding their teeth. We have the catfishes, which have ridges essentially in their shoulder girdle. And as they move their pectoral fins back and forth, they’re creating a stridulatory sound, similar to how crickets and katydids are making sounds. You have fish that are snapping tendons. You have fish that are releasing bubbles out the mouth. Or in the case of herring, it’s actually known as fish farting– they’re producing gas bubbles at the back end.

IRA FLATOW: I’m just stuck at the fish farting comment.

AARON RICE: It never ceases to entertain people.

IRA FLATOW: [LAUGHS] Now, I understand that some of the fish you looked at, you have documentation that this fish has been observed making this noise. But others, you’re saying they just have the right body parts. I mean, how confident are you that they are actually using them to make noise?

AARON RICE: What we see, particularly in fish with really well-developed swim bladder muscles, where we can associate the definitive physiological or morphological experiments and a demonstrated role in acoustic communication– when we have these swim bladder muscles, really the only function that we’re seeing is sound production. And so if we pull a fish out of the water or out of a glass jar in a museum, and we begin dissecting it, and we see these really, really highly specialized deep red muscles on the swim bladder, all of this sort of inference that we have and the data across so many other species would point to the fact that these mussels are highly likely to be involved in sound production.

IRA FLATOW: Now, you know, I have all the same body parts as, say, a professional opera singer. But I don’t sing opera.

AARON RICE: Sure, absolutely. Well, and this is the thing with swim bladder muscles, where the swim bladder itself, if it is only used in buoyancy, doesn’t require a whole lot of intricate musculature, whereas fish that are producing sounds with these swim bladder muscles, these are some of the fastest-contracting vertebrate skeletal muscles that are out there. They have highly specialized sarcoplasmic reticula. They have very specific cell structure within the muscles.

And so these are a group of muscles that we often refer to as superfast muscles, where they stand out from so much of the other musculature in the fish. And so it’s pretty distinctive. And so if we were taking a look at, let’s say, your biceps, and we just see these enormous biceps on your arms, there’s a good chance that you’re going to the gym, working out, or some sort of an athlete, as opposed to if the biceps were atrophied and significantly smaller.

IRA FLATOW: OK, enough talking about fish sounds. Let’s hear some of them that you brought with you today. How about I play some, and you describe them for us?

AARON RICE: Absolutely.

IRA FLATOW: OK, here’s a hum sound produced by the plainfin midshipman.

[LOW-PITCHED HUMMING]

Describe that for us.

AARON RICE: So this is a relatively simple sound. And it may not sound that interesting. But this is a sound recorded by my colleague Andy Bass in his lab along the California coast. And in the rocky intertidal of the California coastline, you have these male midshipmen that occupy a nest and call for females. And while the sound itself doesn’t sound that spectacular, these male fish will continue singing for over an hour nonstop.

And so what’s amazing to me is you have this really, really highly specialized muscle producing these sounds. And so while the acoustic display itself may not be particularly captivating, it’s the underlying mechanics of it and the behavior that are just so intriguing. And you can imagine, too, that if you’re out there, you have these colonies of nests pretty much next to each other scattered across the beach. And these sounds from fish, from the midshipmen, would really dominate the soundscape.

IRA FLATOW: OK, let’s go to some hoots produced by the freshwater toadfish.

[LONG HOOTING SOUNDS]

Wow. Tell us.

AARON RICE: This is actually one of the first species I studied when I came to Cornell many years ago. And it was one of these things where we know that toadfishes are really sort of these loud and obnoxious species of fish. And so we saw this species pop up in the aquarium trade, and it’s like, huh, we don’t know anything about this species. But certainly being in upstate New York, where we don’t have a lot of ocean that’s readily accessible, if we could maintain a freshwater species of fish, that’s certainly logistically easier. So we got it in the aquaria, put in our little hydrophone, let it record sort of overnight. And lo and behold, these really unimpressive-looking fish started making these just really wild and crazy sounds.

One of the things that’s so neat about this freshwater toadfish is it has, actually, a completely different swim bladder structure than all of the other toadfishes. So midshipman, the Gulf toadfish, have these sort of heart-shaped swim bladder, but the freshwater toadfish actually has two physically separated swim bladders that almost look like lungs. And it allows them to produce this sort of wild repertoire of sounds with crazy characteristics compared to closely related species.

IRA FLATOW: All right. Let’s listen to black drum sounds.

[DEEP CROAKING SOUNDS]

Sounds like– right there, it did sound like a bass drum for a second.

AARON RICE: Absolutely. These are such a great species. So these guys are loud. They’re obnoxious. The source level on black drum calls underwater is about 165 decibels, which if you do some rough comparisons with things in air, it’s about as loud as a jackhammer.

IRA FLATOW: Wow.

AARON RICE: And what’s great is that these fish, when they produce these aggregations, where males– just tons of males– are calling for females. And these calls and this chorus, with 165-decibel sounds, lasts for six to 10 hours during the spawning season, every night for months. During the summer, if you think crickets are obnoxious in the backyard, imagine this deafening sound within the soundscape.

[DEEP CROAKING]

IRA FLATOW: Yeah, it almost sounds like propellers from a boat.

AARON RICE: And it’s just this, you know, one boom after another. One of the things that’s really been exciting in this field of bioacoustics is, as the technology increases in its sophistication, we can start visualizing and listening to and understanding sounds in the natural world in ways that were unthinkable years or decades ago. And so when we take sounds from these recordings that may be months to years in duration, and we look at six months of sound within a single window on the computer, the overwhelming sound that pops out along the Atlantic coast are these black drum choruses. They’re just extremely obvious. And then if you sort of zoom in and start listening to it, yep, these are distinctive sounds from these fish as they’re calling during the spawning season.

IRA FLATOW: If you want to see some of these noisy fish, you’ll find pictures on our website, sciencefriday.com/fishsounds. I’m Ira Flatow, and this is Science Friday from WNYC Studios. OK, next sound is the Bermuda sound, a bunch of fish recorded on a reef in Bermuda. And we have no idea what they are.

[LOW PURRING SOUNDS]

AARON RICE: One of the reasons why I wanted to bring this sound in particular is this highlights the central conundrum of where we are in the field. We have really sophisticated sensors that may be the size of a water bottle that we can chuck over the side of a boat or put down when scuba diving on the sea floor. And they’ll record for weeks to months to years unattended, and then we bring it back to the lab. And what we see when we record in oceans, lakes, and rivers around the world is the vast majority of biological sounds we’re getting are produced by fish. But we have no idea what species they are.

So we have– for about 1,000 of the 34,000 species of fish, we may have some degree of vocal recordings and can match species to sounds. But for the vast majority of aquatic ecosystems around the world, we know they’re fish sounds, but we have no idea who’s producing them. So the sound in Bermuda, where it is exciting– you know, coral reefs get so much attention. But when we start to get these sounds, and we’re sort of closing our eyes and listening, it’s pretty clear there’s quite a bit of activity. And it immediately raises the question of, well, who’s making these sounds?

That particular sound sort of sounds like pigs in a pigsty. And we can start to guess who they might be. But at this point, we really don’t know. And this is where so many of these fundamental questions in the field are that sort of cause me to get out of bed in the morning.

IRA FLATOW: [CHUCKLES] So how do you go about figuring out what they are? Do you put microphones in the water and just wait and watch?

AARON RICE: We use as many different approaches as we can think of. So the easiest case would be something like we can do with the midshipman or that freshwater toadfish, where we can bring them into the lab, we can make them happy and healthy, put a hydrophone in the tank, and then just be patient and hope they do their thing. And in some cases, that’ll work. In other cases, we’ll be able to do underwater vocal recordings combined with visual observations such that we can actually be looking at a species when it’s making sounds and sort of match sounds and species that way.

In other cases, we can start with looking at the morphology or the physiology and then do some sort of electrophysiological stimulation of the muscles and record simultaneously and sort of hear these fictive sounds that are made. And in some cases, too, then we have this level of inference where if we’re recording at a certain point in time, and we’re getting all these sounds, and there are other supporting surveys or visual information that says, well, the only thing that’s there is species X, this overwhelming sound that we’re getting must be produced by that species. With 34,000 species of ray-finned fish, there’s plenty to keep us busy.

IRA FLATOW: I’ll bet. And you know what’s interesting to me is that you’re at the famous Cornell Ornithology Lab, which studies, what? Bird sounds.

AARON RICE: Well, the tagline on the building is that it’s the Center for Birds and Biodiversity. And so our lab group at the K. Lisa Yang Center for Conservation Bioacoustics, we very much encompass listening to the world and all of its critters through this perspective of sound.

IRA FLATOW: And how come we’re just hearing now? We’ve been hearing about bird sounds from Cornell for decades, but not fish sounds.

AARON RICE: I have my own speculations and biases. But the idea of fish sounds, it’s been around since Aristotle. You know, this is a 2,000-year-old field of natural history and science. But it’s always been seen as this sort of esoteric oddball.

And the number of people actually engaged in the field has been a small group of scientists. We read each other’s work. You know, there’s been some wonderful monographs over the decades. But now, with sort of this increasing awareness of how pervasive not only biological sounds, but human sounds, are in aquatic ecosystems, I think there is this increased attention of the importance of fish communicating with sound.

IRA FLATOW: That’s quite interesting. Is it possible, if I go snorkeling or scuba diving and be very quiet, that I could hear some of these fish sounds?

AARON RICE: Yup. One of my formative experiences as a grad student was snorkeling in Cape Cod when I was in Woods Hole. And as you float over the nest of a calling oyster toadfish, your entire body will vibrate. It’s this just really surreal feeling, where you have these fish in and among the algae– you can’t see them, but you can absolutely hear them, unassisted, without hydrophones. And it is just a really loud sound that just resonates through your lungs, your ears, and your body. If you happen to be in someplace like Hawaii or the Western Pacific, there’s a number of different damselfish species or grouper species that are making sounds that you can readily hear without the use of additional technology.

IRA FLATOW: It sounds like you have a really boring job, Dr. Rice.

AARON RICE: It keeps me busy.

IRA FLATOW: I want to thank you for taking time to be with us today. Great stuff.

AARON RICE: This has been so much fun. Thank you, Ira.

IRA FLATOW: Dr. Aaron Rice, principal ecologist in the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology in Ithaca, New York.

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