Environment
Award-winning journalist Amorina Kingdon explores how marine animals use sound to survive and the ways humans are impacting critical underwater soundscapes
Excerpted from Sing Like Fish: How Sound Rules Life Under Water by Amorina Kingdon. Copyright © 2024 Amorina Kingdon. Published by Crown, a division of Penguin Random House Limited. Reproduced by arrangement with the Publisher. All rights reserved.
Rodney Rountree drags a wheeled handcart out on the Cotuit Town Dock and unloads his kit: a hydrophone in a pelican case, over-ear headphones, a folding lawn chair, a bucket, a fishing pole. Rountree (whose sweatshirt reads on a clear night, i can hear the fish laughing) baits a black mesh crab trap with a small can of squid chum and tethers it to a salt-pale wooden post. Through the hydrophone comes the swish-plunk sound of the trap splashing into Nantucket Sound. It’s a June evening on the south shore of Mashpee, Massachusetts, the sky is cotton-candy-colored, and in the waters around us, cusk-eels are mating.
Rountree is known as the Fish Listener. Jovial and gray-haired in a bright Hawaiian shirt, he’s an adjunct professor at the University of Victoria and often works with Francis Juanes and his lab. He’s based in Cape Cod and has listened to fish for more than three decades. His methods are mostly simple: go into the field, drop a hydrophone, and record. He has spent years listening off boats, coastlines, and docks, in deep seas, in freshwater and salt, and developing hydrophone arrangeExcerpted from Sing Like Fish: How Sound Rules Life Under Water ments, recording tactics, site selection, and “the long-term, tedious, detailed work” of the field naturalist.
“I’m pulling out all the stops to see if we can audition something,” Rountree, a native of North Carolina, says in his soft drawl. He unloads a paint bucket, in case the trap yields something. I hear a few muted boops, which Rountree says are oyster toadfish, a relative of the midshipman. But the clearest signals, the ones we’ve come to hear, are cusk-eels. And I hear them right away. They have a chattering call, staccato bursts, like wind-up dentures.
Cusk-eel are not a single species, but several hundred or so. They’re bottom-dwellers that live throughout the sea, from shallow water down to deep ocean trenches. They are eel-shaped but are fish, about 25 centimetres long, and like the midshipman, they make sounds by vibrating muscles against their swim bladder.
As the sun sets and we listen, Rountree tells me this dock is where he first realized that cusk-eel lived in these waters, by inadvertently recording their sounds.
It was the cusk-eel that first piqued Rountree’s interest in fish sounds. A graduate student at Rutgers University in New Jersey in the late 1980s, he was working with a colleague who mentioned to him that cusk-eels made sounds. Intrigued, he captured some of the fish from the warm water intake of a coastal nuclear power plant where they sometimes congregated. Together they studied the fish in the lab. Cusk-eels spend the day living in the sediment and, at least in shallow waters, only come out at night. To Rountree’s surprise, they heard eels making sounds while buried in the sediment.
He started reading up, beginning with Marie Poland Fish’s collected studies, Western North Atlantic Fishes. He found recordings of cusk-eels taken near Woods Hole in the 1950s, though the sounds were then labeled erroneously as those of a sea robin. It was the same circular problem that’s plagued researchers since the days of the “biologicals”: If you don’t have a sound ascribed to one fish, and you can’t see the source, you can’t confirm who’s making the sound.
In 2001 Rountree surveyed Stellwagen Bank, just north of Province- town, with Francis Juanes, and they came up with the idea of triangulating the fish sounds using a small array of several hydrophones and a camera. With sound alone, you couldn’t figure out the source, nor with video alone: Fish, unlike humans, don’t move their mouths when they “speak.” But an array of hydrophones separated by a meter or two and accompanied by a camera could triangulate where a sound originated. By cross-checking audio with video, hopefully, you would see a fish at the “source.”
After the Stellwagen study Rountree bought a folding clothesline tree, stripped the lines from the tetrahedral metal frame, lashed a hydrophone to the end of each arm, and added a camera. Later iterations evolved into cubic frames of PVC piping. It was off this very dock, he says, that he tested these prototypes, and it was this design that Kieran Cox was testing back in 2016 when he first told me about fish sounds.
Through our headphones now comes the clinking chain of a nearby buoy, along with some mysterious sounds: A distant bass string plucked. A growl, just loud enough that we both look up, surprised. Rountree isn’t sure what it is. Even after all his auditions and arrays, most sounds remain mysteries.
The trap does, eventually, yield a furiously squirming cusk-eel. Rountree gently guides it to the water-filled bucket, drops in the hydrophone, and together we listen. Nothing. He stirs his hand through the water, gently picks up the eel. Nothing. Ah, well. Not every fish wants to be a star.
Back at Rountree’s sprawling home, in a verdant cul-de-sac, a small plastic-sheeted greenhouse stands in the driveway. As we pull up, I see it’s a white PVC frame from one of the underwater array prototypes, now sheathed and repurposed for seedlings.
Over the next few days, I pace Cape Cod’s sandy, sun-drenched shores, hydrophone coiled at the ready. In warm summer rain, halfway down the Provincetown jetty, only invertebrate crackles and clicks. Off the beach at West Dennis, the hiss of sand and waves. Near the Falmouth Yacht Club, just the mosquito-like drone of boats. I rent a paddle board at the Bass River, slide my hydrophone into my backpack, and head seaward.
The water is murky and nearly opaque. I don’t realize I am paddling over a sandbar until the board’s fin scrapes the bottom; when I step onto a knee-deep sandbar near the river mouth, I can’t see my feet. Any fish trying to communicate here would have to use sound.
And that might be tricky. On this bright, warm day with a stiff breeze, motorboats cruise constantly back and forth past kayakers and paddle boarders like me, and I brace against a jostling wake every few seconds.
Yet between each motor, I hear it: the cusk-eel’s telltale knock. I drift down the river, hydrophone trailing behind me. In the vessel-clogged waters directly opposite the Bass River Yacht Club, the cusk-eel chorus rises highest, each voice chattering over another, accompanied by a gentle chorus of toadfish boops, layered like synthesizer notes. It’s beautiful. I stop, glide, listen. Fish are singing, even here.
Perhaps the noise doesn’t bother them. But then, it’s mating season in their murky home, and sound is how they find each other. Perhaps they don’t really have a choice.
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