The Fish Listener

Snap, chirp, squeak. BARK! Puuur, grrr, thump. Huuuum, hoooot, creeeeeak. SNORT! Ppffffffffft.

The animal making these sounds is actually human. His name is Rodney Rountree ’87 (M.S.), and don’t worry – he’s not crazy. (Well, maybe a little?) When NPR or a writer from your alumni magazine or a random fisherman asks about his area of research – fish sounds – he just wants to make sure we get the full picture. Yes, fish make noise, and Rountree has spent the past two decades of his career as a marine biologist trying to figure out which fish make which sounds, when and why. He has listened to fish in marine habitats from the Gulf of Mexico to the Gulf of Maine, as well as those in freshwater habitats from the Amazon River in Peru and the Virgin River in Utah, to the many rivers, lakes, ponds and streams in New England. And he’s out to prove these ecosystems are not silent.

Roar, thunk, thunk, thunk, slam. “Do you want something to eat?” Slam, thunk, thunk, thunk, roar.

It’s late February, and these are the sounds along the banks of the Cashie River in Windsor, N.C. The wind is fierce today, making it difficult to hear much. Except the thunk of trucks over the bridge on Route 17, the slam of car doors and the shouts of people at the Speedway gas station that sits beside the river.

Rodney Rountree parks his van at a small park near the bridge and approaches a fisherman tossing in his line from the grassy bank. Rountree’s walk over to the man is purposeful. He did not get out of his van to enjoy the scenery, eat lunch at the picnic table or make small talk. The fisherman doesn’t know it, but this is a business conversation.

“What’s biting?” Rountree asks.

“Nothing,” the fisherman replies.

Rountree gets back into his van and drives to the back of the Speedway on the opposite side of the river. He’s quite familiar with this spot. For years, it has served as a resting point on family trips to visit his parents in North Carolina. His daughter had her first taste of grape soda in this very parking lot.

Today, Rountree is not here for grape soda or gas or the restroom. It’s the boat launch docks behind the gas station that interest him. It’s here that he brings a small stool and two small plastic bins, which contain his equipment: a recording device, hydrophone (a microphone that can go underwater), headphones, extra batteries, a camera, notebook and pens.

Rountree sets up the recorder, snaps some photos of the area and writes the date, time and location in his small notebook. Then he drops the hydrophone in the water, sits on his stool and listens.

With the wind still roaring and the trucks still thunk thunking, it’s easy to imagine a quiet world beneath the surface of the Cashie. But it’s not. Underwater, the thunks are still there, and Rountree can also hear the plop of the fisherman’s line hitting the water.

And now there is a constant snap snap snap snap. Rountree tries to deduce what it could be. It sounds like snapping shrimp, but the timing isn’t quite right. And he’s too far up the river. Maybe hickory shad? They’re just starting to run.

Rountree listens for a while longer and jots some more notes before packing his things into the van to head to the next spot on his list.

Fishy Business

If you could sum up Rountree’s childhood in sounds it would be this: the lapping of the Shark River against its bank, a happy shout when he or one of his five brothers caught a fish, Jacques Cousteau specials playing on the television and a certain sob story he used to tell fishermen on the docks near his home in Monmouth County, N.J. The story was a scam he helped his older brother Elton run. Elton would take him down to the docks right when the fishing boats were coming in and hide out of sight while a 6-year-old Rountree went up to the men bringing in the fish and cry about how he couldn’t catch anything to bring home to his mother. For a while, the scheme worked. It seems the fisherman couldn’t resist Rountree.

“Here you go,” they’d say, handing over a fish. “Tell your mom you caught it.”

Until one day, they got busted, and Elton had to pay for the fish. That was the end of the scam, but not Rountree’s interest in fish. He loved the water. He had a seashell collection and a stack of children’s books on oceanography. Perhaps it was in his genes – Rountree comes from a long line of fishermen on his mother’s side who settled in the Outer Banks of North Carolina, near Morehead City. His grandfather was a charter boat captain who built his own boats, and when Rountree came to visit, his grandfather took him down to the Triple-S Pier on Atlantic Beach to fish.

On the Shark River in New Jersey, Rountree caught tinker mackerel and snapper blues with cane fishing poles, and he and his brother Peter would sell blowfish for 10 cents each to old ladies on the beach. One winter, sitting in the cold with snow around him and a Jon-e warmer in his hand under a sock, he caught seven winter flounder. Rountree and his brothers Billy and Elton sometimes went out to the jetties late at night to fish for striped bass, and once Elton took Rountree on a head boat to catch bluefish. Rountree was seasick most of the time, but he caught seven big blues.

Rountree would go on to study marine biology at the University of North Carolina Wilmington (UNCW), where he took an ichthyology class with David Lindquist that led to his decision to specialize in the field. One day on summer vacation, he was fishing from the Triple S pier, watching little fish follow around some cannonball jellyfish. Rountree snagged one of the jellies, managed to haul it up to the pier and found one of the little fish inside. That led him to investigate the symbiotic relationship between the two during his time at UNCW, which in turn led him to study the association of fish with drifting materials of all kinds when he came to the College of Charleston in 1983.

When Rountree was considering graduate schools, he wanted to go where the ichthyologists were. The College of Charleston had seven listed on their staff, while most schools had none. And while he was presenting the results of his UNCW research at the annual meeting of the American Society of Ichthyologists and Herpetologists, he met George Sedberry, a professor in the school’s graduate marine biology program, who encouraged Rountree to apply.

“It was very unusual for undergraduate research to be presented at this international meeting, and I was impressed,” says Sedberry.

And Rountree continued to impress as the two began to work together. Not only did he already know the research he wanted to do for his thesis (also unusual for a new graduate student, Sedberry says), but he had ideas about how to get his work funded.

“Rodney’s research involved complicated and expensive offshore sampling logistics, and was quite different from what was being done in South Carolina,” says Sedberry. “He couldn’t piggyback on an existing research program. He had to independently find funding and arrange logistics, and he was successful.”

As Rountree set out to figure out why fish were attracted to flotsam, he had to build fish aggregation devices (FADs) in order to attract fish. On his first attempt, he bought material to build rafts, and his mother sewed streamers to hang underneath. He lost them all within days. His second attempt, made from PVC pipe and plastic straps, came up in a giant mess after a hurricane. His third attempt was successful, and he used a team of divers to help locate his underwater, unmarked FADs. Sedberry says Rountree’s research inspired other students to continue SCUBA-based observations on fish behavior.

Rountree’s work resulted in two published papers (and a third 20 years later), and he says his experiences at CofC prepared him for branching out into other areas of research. “The program was great because you had the academic portion, and then you had this ongoing work in all different disciplines – from hardcore systematic ichthyology to mariculture and pure fisheries work.”

According to Rountree, with the amount of material covered, the College’s marine biology program was pretty much a doctorate program – except on paper. So, after graduating in 1987 with his master’s in marine biology, Rountree earned his Ph.D. in ecology and evolution from Rutgers University five years later under Kenneth Able. He then went on to manage multidisciplinary estuarine and fisheries programs for the National Marine Fisheries Service (NMFS) and the University of Massachusetts Dartmouth. Rountree later served as a senior scientist for a consulting firm that focused on identifying new technologies needed for marine ecology and conservation studies, and as an adjunct instructor at the University of Massachusetts Amherst. During these years, he researched food web structure on the northeast continental shelf, managed Atlantic cod and yellowtail flounder tagging projects and trawl surveys, and published papers on everything from the foraging habits of juvenile smooth dogfish to the fish community structure in the saltmarsh creeks of southern New Jersey.

But it wasn’t until the late 1980s that Rountree began recording fish sounds.

Sound Career Choice

Rap-rap-rap-rap-rap. Rap-rap-rap-rap-rap.

That sound, to the layman, is a cross between a woodpecker and a jackhammer. For Rountree, it’s what launched his interest in fish sounds. And to the female cusk eel, rap-rap-rap-rap-raps are incredibly sexy.

In the late 1980s, when Rountree and a colleague, Jennette Bowers-Altman, were researching cusk eels in a lab at Rutgers, they weren’t focused on listening to the sounds of the fish. Instead, they set out to be the first scientists to record the cusk eels’ spawning behavior. Then they discovered that, around the same time each night, the male fish made these loud raps, a call that seemed to be a part of their spawning ritual. Rountree and Bowers-Altman recorded the noises and later, with another scientist, published a paper – the first ever to describe the sounds of that species of fish. A decade later, when Rountree learned about researchers using sound in marine ecosystems to track dolphins, he wondered if sound could also be useful as a way to identify fish and their behaviors.

Scientists have known for a long time that fish make noise – Aristotle was describing fish sounds more than 2,000 years ago. Besides naming some fish for the sounds they produce (drums, croakers and grunts, for example), however, we’ve done very little with that information in fisheries and conservation fields.

Which is silly, if you think about it. As Rountree puts it, “Imagine studying birds, but ignoring their sounds.”

Not all species of fish make noise, but most make some sort of incidental sounds, like the grinding of food between its teeth or the movement of air between its swim bladder (a gas-filled bladder that controls buoyancy) and internal organs. Fish also vent that excess air through their gills, mouth and anal vents, creating coughs, burps and, yes, farts.

The first time Rountree heard a fish fart, he was in a remote area of Maine, near Moosehead Lake, in 2008.

Creeeaaaaak.

“As far as I knew at the time, only two fish in the entire world made that kind of sound: Atlantic herring and Pacific herring,” Rountree says. “There was nothing like that where I was listening, so I was excited.” (Fun fact: Rountree isn’t the only one who gets excited about fish flatulence. His website, fishecology.org, features downloadable fish ringtones. The fart has been downloaded more than 100,000 times.)

For humans, passing gas is a natural, biological process, a byproduct of our system digesting what we eat. For fish, the act could be a form of communication. In 2003, scientists discovered that Pacific and Atlantic herring (saltwater fish) were controlling the release of their gas. The more herring placed in a tank, the more they noticed streams of bubbles expelled from the fish’s anuses, which coincided with a fart sound. The herring only seemed to be noisy farters after dark, leading researchers to believe these sounds allow the fish to find one another when they can’t be seen.

It took Rountree a decade to convince other scientists that the noise he heard in Maine was also a fish fart. His paper, finally published in 2018, discusses air movement sound production by freshwater fish, including alewife, white suckers and brook trout. In the study, it was unclear whether the air movement sounds were just physiological or intentional. Even if they were incidental, the noises seemed to be unique to each species and showed the possibility of using these types of sounds in identification.

Intentional noises can also be distinct to each species. These sounds resemble everything from snaps and croaks to snorts and hums, and are used to help a fish attract a mate, ward off predators or defend their territory. Some fish, like haddock, cusk eels and toadfish, do this by using a sonic muscle to “drum” on their swim bladder. Others use stridulation – rubbing hard body parts together, like teeth or jaws. Body movements that create water currents or splashes are also used to communicate.

When Rountree sets out to listen to these sounds, he’ll spend anywhere from 15 minutes to months at a time recording in a particular area. Sometimes he’ll “audition” fish: If there’s a fisher nearby with a live catch on the line, Rountree will bring over a little kiddie pool, place the fish inside and record any noises. Once the sounds are recorded, Rountree uploads the files to his computer and uses a special software that displays the sounds graphically in terms of frequency and intensity across time. From that, he can learn to identify the noise.

“We can say, ‘Based on this sound, we know this fish is here.’ Or, ‘Based on this sound, we know this fish is doing this particular activity.’ That’s a powerful tool in biology,” Rountree says.

Sounding the Alarm

When Rountree first began doing this type of research, there were few others doing anything like it, at least in terms of freshwater ecosystems. In recent years he says there’s been an explosion of sorts, which he attributes to the increase in awareness of the potential impacts of noise pollution on marine mammals. Might those same noises also be impacting freshwater habitats? If our cars are thunking over bridges and our boats are vrooming through waterways, are we at risk of losing those rap-rap-rap-rap-raps?

For most of the year, humans don’t hear much from a type of toadfish known as the midshipman. Until the spring. Then hoards close in on the coastline between Alaska and Baja, Calif., to breed. It’s here that the male fish sing to attract a mate, vibrating their swim bladders up to 150 times a second and producing a prolonged hum that can last for more than an hour at a time. It’s a song people have described as a chorus of kazoos, a drone of bees and the chanting of monks.

Back in the 1980s, people didn’t know this about the midshipman. In Sausalito, Calif., a community of houseboat residents complained of a humming sound that lasted from sundown to sunup, the volume ranging from that of an electric razor to an airplane engine at full throttle. They thought the sounds came from Russian ships ready to invade California, or even from UFOs. When marine scientists began to investigate, they found that an unusually large number of midshipman were making their nests along the shore that year, and their combined calls resulted in the strange sound.

The song of the male midshipman was so loud those years that many houseboat residents said it disrupted their sleep. They didn’t need to drop a hydrophone in the water to hear it. So, it begs the question: Do we ever make so much noise that it affects fish?

Rountree says it’s possible that human sounds are impacting fish’s ability to communicate as well as their ability to take cues from sounds in their ecosystem. There’s an analogy he uses during some of his lectures: If you’re walking down the street of your neighborhood, you might hear a car behind you, a kid yelling down the street, somebody mowing their lawn and the sound of a sprinkler. As you’re walking, your mind is unconsciously building a spatial map from the sounds you hear.

“That’s important,” Rountree says. “When you hear the car behind you, then you jump out of the way. It’s the same with fish. If something is making it harder for them to hear the natural soundscape, then that’s a problem.”

While some lakes and rivers remain untouched by human noise, there are many that have roads running alongside them, bridges that cross them and boats that motor through them. These sounds, in addition to noise from planes and trains, can be heard underwater.

In his most recent study, published in the open-access journal PLOS ONE in March 2020, Rountree and a group of colleagues recorded 2,750 minutes of underwater sounds in 173 locations consisting of lakes, ponds, rivers and streams representing five major river systems in New England. The scientists identified more than 7,000 distinct sounds, which they categorized as anthropogenic, biological (made by animals) or unknown in origin.

The group discovered that anthropogenic sounds – those produced by human activities, like the noise from a car or boat – account for more than 90 percent of the underwater soundscape in major freshwater habitats of New England. They also found that areas with higher overall sound levels had a lower number and diversity of biological sounds, and that the timing and acoustic features of anthropogenic sounds often overlapped those of the biological sounds.

Which means that a fish trying to attract a mate may be drowned out by cars rumbling on a bridge over the river. Or a fish might have difficulty hearing the sounds of waves to navigate a shoreline. Extremely disruptive sounds, like pile driving, can even cause fish physiological damage.

The results of Rountree’s study suggest that there’s a potential for human sounds to impact freshwater soundscapes negatively. While more research needs to be done to assess these threats, scientists have already noticed what’s happening in marine systems: A recent study found that underwater noise from anchored and moving vessels not only displaces Arctic cod to areas with less noise, but also changes their swimming behaviors. Freshwater fish may suffer the same fate.

“There’s a cacophony of underwater sounds that are in danger of being lost because of anthropogenic sounds – and before scientists even know those underwater sounds are there or what they are,” Rountree says.

Mystery Noise

HONK! Hum. Scratch scratch scratch. Rountree’s website is full of these unknown sounds. He’s saved them in the hopes that someday he’ll be able to know what fish made each sound and why. The site is full of other grunts, groans and growls that he has identified: the rumble of a haddock, the croak of, well, a croaker.

Rountree is semi-retired now, but in the spring, he heads to the University of Victoria in British Columbia to work with their Fisheries, Marine Ecology and Conservation Laboratory as a visiting scientist and adjunct professor. The lab is run by Francis Juanes, who Rountree met while based at Rutgers’ marine field station in Tuckerton, N.J. Juanes was a grad student at Stony Brook University, but traveled to the station for sampling.

Juanes says his lab is large, and he can’t always provide one-on-one mentoring. Having an expert like Rountree on hand (and he is on hand, even from his home in Falmouth, Mass.) has proved to be invaluable. Not only is Rountree a great sounding board for new ideas, but he spends large amounts of time helping to mentor students.

“He is definitely one of the most dedicated scientists that I have ever known,” says Juanes. “It’s not easy to remain interested and dedicated when you’re an independent scholar. But Rodney’s love of science and fish has always shone through.”

He says Rountree’s dedication is exemplified by the many field trips he has undertaken – usually alone, usually at night and usually lugging equipment to be able to record that one species that has not been recorded before. Throughout his career, Rountree has auditioned piranhas, been stabbed by catfish tails and debunked the myth that the Champ, a monster thought to live in Lake Champlain, was the one making some weird sounds in the lake. (The culprit? A drum fish.)

Rountree can’t help but work with fish. He has a fishpond at home. He drops his hydrophone into mountain streams on hikes or, once on vacation in the Florida Keys with his wife, Barbara, he ran it out the window of their vacation rental, one end in the water, the other plugged into the television so the VCR could record the sounds. He and his wife struggled to sleep over the sounds of the toadfish.

Fortunately, Barbara is understanding. “I play golf, he drops his hydrophone,” she says. “We all have our hobbies.”

Barbara has had her own career with fish, recently retiring after 31 years working as a fisheries economist in the social sciences branch of the National Oceanic and Atmospheric Administration Fisheries in Woods Hole, Mass. The two met in the first-floor hallway of the NFMS lab building, and Barbara invited him to get a beer after work with a group of friends.

“He had a ponytail, wore tight shorts and often wore a leather cowboy hat,” says Barbara. “What a picture, right?”

Still something must have clicked. Their first official date was on a Thanksgiving weekend, and Rountree proposed the following January. Barbara thought it was too soon and said no, but a month later they were engaged. They have been married since October 1993. The couple has a daughter, and Rountree used to think up children’s stories for her on the way home from work, sitting in Cape Cod traffic. (The story of Dr. Shrimp and Mr. Grouper can also be found on his website.)

Over the years, as Rountree’s work has been featured in outlets like NPR, Discover Magazine and a blog for National Geographic, he has been asked one question a lot: How does he know it’s fish making these sounds?

“A lot of times, I don’t,” Rountree says. “Many of these sounds aren’t known. There has been reluctance in the past to study these things when you didn’t know exactly what it was. But my argument is, that’s just part of the process. You have to do the work to understand these patterns to figure out what it is.”

Rountree used to travel all the way to New Jersey from his home in Massachusetts to record those rap-rap-rap-rap-raps of the cusk eels because they weren’t thought to live around Cape Cod. Until one night when Rountree stood on a dock in Cotuit Bay near his home and heard the species’ distinct call, so loud it was like a jackhammer underneath his feet. And when his undergraduate student, Katie Andeson, at the University of Massachusetts thought she heard drum in the Hudson River and everyone told her there weren’t any drum in the Hudson River, Rountree completed his own survey, documenting that, yes, there are freshwater drum who travel through the Erie Canal system from Lake Erie, and the Champlain Canal from Lake Champlain, down into the Hudson.

Proving you just never know what you’ll hear until you take the time to listen.

Rountree currently has a mystery noise he’s working to figure out. It’s one of the biggest sounds he has ever heard in a freshwater system: a low, rumbling roar that goes on for about an hour around sunset. The noise seems to only occur in the tidal regions of a few rivers he’s recorded in. Because of that, there’s only a handful of fish it could be, but the sound doesn’t quite fit with any of these species – at least with what scientists know now.

“It’s that sense of discovery that really attracts me,” says Rountree. “A lot of the places I’ve explored, no one has ever dropped a hydrophone in the water. A lot of those sounds I’ve recorded, no one has ever heard them before. To me, that’s pretty cool.”