You might not think of most undersea creatures as a noisy lot, but one fish researcher in Florida studies his subjects with the use of hydro-phones. And what he hears may surprise you. Angela Swafford reports.
CURWOOD: You may have heard the songs of the humpback whales and the energetic clicks of dolphins. But if you think those are the only voices of the sea, think again. Grant Gilmore studies fish by eavesdropping on their chatter. Mr. Gilmore does his listening at the Canaveral National Seashore, a wildlife refuge that's part of the NASA complex in southern Florida. Angela Swafford reports.
(Water against boat hull)
SWAFFORD: There's a full moon tonight over Mosquito Lagoon, a 45-mile-long estuary surrounded by a thick mangrove forest. Look to the south and you'll see that the launch pad at the Kennedy Space Center is also in full glow. At daybreak tomorrow, the shuttle Atlantis will blast off. In the meantime, marine biologist Grant Gilmore is preparing his own mission.
GILMORE: Thank you. We're in the basin opposite marker 19, and the time is 7:55.
SWAFFORD: A towering man with striking white hair and beard, Dr. Gilmore is collecting some last-minute data from the deck of an 18-foot skiff. He and his team prepare to launch an underwater microphone. The three-inch device is already on as it hits the water, so it records the
sounds as it plunges down.
(Scraping, various sounds)
GILMORE: That pupupupupupupuk sound is a silver perch. Sounds like chickens cackling. The boom, boom is a black drum. The ruur, ruur, ruur is a spotted sea trout. So we have three species of scianidaes, drums and croakers produce these sounds at the same location here.
SWAFFORD: These are the voices of the nocturnal sea. And Dr. Gilmore is one of the few scientists in the world who studies their meaning.
GILMORE: This is one very large black drum.
SWAFFORD: More than two decades ago, Dr. Gilmore discovered this cacophony is actually the sounds of spawning. Males do most of the serenading. It's their way of convincing the females to release their eggs. These sounds reach full crescendo on full moon nights. That's when the high tide is likely to prevent the eggs from being carried out to sea, where they would have little chance of surviving.
(An engine starts up)
SWAFFORD: Dr. Gilmore and his assistants are making their monthly rounds tonight. Twenty metal markers scattered throughout the lagoon identify the sites where they'll hunt for sound. The team stops at one.
GILMORE: We're about 200 meters from the bridge. Time's about 6:20 PM.
(Microphone plunks into water; crackling)
GILMORE: You hear the crackling sound. Those are snapping shrimp; they're only about an inch long. And they have one enlarged claw. It sounds like frying bacon in a pan.
SWAFFORD: They produce this frying bacon sound by snapping that claw. The humming in the distance comes from toad fish that like most fish produce sound by vibrating an air bladder in their body. It is played like a drum by a set of strong muscles. Dr. Gilmore calls them sonic
muscles, and he found that females almost never have them. But that doesn't mean Dr. Gilmore is not interested in female fish. He's trying to find a way to figure out how they react to these love calls.
GILMORE: That male could be calling for three hours and no one will pay any attention to him. We wouldn't know that because we don't know which sounds the female, or how the female's reacting, because she's not producing sound.
SWAFFORD: Dr. Gilmore's fascination with fish sounds began with a little bit of professional jealousy.
GILMORE: Well, I had a friend who studied birds. And he could walk through a forest and tell me which birds were in that forest. And I was impressed with that. I had another colleague who stuck a hydrophone in the water one day at my laboratory, listening to large-mouthed bass, and
I put it all together. I wanted to see if there was anything producing sound out here that you could identify like the birds.
(Sounds fade to chimes)
SWAFFORD: Dr. Gilmore's passion for fish even influences his home decorating scheme. A fish chime hangs from his front door. Fish swim on his kitchen dishes and over his bathroom towels. And while his study is crammed with a quarter century's worth of fish recordings, Grant Gilmore
does appreciate their non-auditory qualities.
SWAFFORD: He also sketches the fish he studies
GILMORE: When you preserve a fish in chemicals, which fix the fish for hundreds of years, first things that go are the reds and the yellows. You never can get those colors back again. So, these are the very important colors for me and my work. Quite often these fish are new species, or at least the first time we've seen this color pattern. So we try to record those colors.
(Sketching, fading to water sounds)
SWAFFORD: Back on the lagoon, a drama is about to unfold.
GILMORE: There you go. Here you go, that's a dolphin.
SWAFFORD: Under the tapping sound coming from the perch, you can faintly hear what sounds like a creaking door or something like a fishing rod being reeled in. Let's listen again.
GILMORE: Here you go. So when the dolphin produces that sonar, the fish pick it up apparently, detect it, and they're quiet. Right now we don't hear the bardial right now. The dolphin is probably right in the middle of this group of silver perch underneath our boat.
And it's very possible the dolphin took a fish down there; we can't tell. Everything's quiet and serene up here. (Laughs) But there's a big drama going on down there. The fish are being terrorized and eaten by this dolphin.
SWAFFORD: Dr. Gilmore and his team are thinking of heading home.
GILMORE: See, everything's quiet right now.
SWAFFORD: It's midnight, and the only creature still sounding off is a toad fish. Well, almost the only one.
GILMORE: Ah, there's one last silver perch. (Laughs) Now, that's the last male silver perch calling. Why do you think he's calling now?
MAN: The last guy left in the bar at the end of the night.
GILMORE: (Laughs) Yeah. He's still trying. (Laughs) Maybe he'll have
more luck tomorrow night.
SWAFFORD: Ever since he first plopped a hydrophone in the water, Grant Gilmore has been convinced of the power of sound as a tool to study marine life. He plans to install an array of permanent hydrophones in this lagoon so he can monitor the fish from his lab. Dr. Gilmore
believes that hydrophones can also be used to protect marine sanctuaries from trespassers, alerting patrols when fishing boats are in the area. The 54-year-old also hopes to rig a submarine with hydrophones, to listen to the sounds of the deep ocean. He's logged over 300 dives in
submersibles all over the world and identified a dozen species of fish, including one named for his wife. But Gilmore says the water still holds mystery for him.
GILMORE: Here I am where they launch rockets to deep space. Just a few miles from here man went to the moon. Left Earth right here and went to the moon. More men walked on the surface of the moon than went to the deepest point of the ocean. We have not explored the ocean yet.
SWAFFORD: Even NASA is now working with sound. The agency is collaborating with Dr. Gilmore to develop more sophisticated listening equipment. Initially it will be used to explore the Earth's oceans, but one day NASA might use this equipment on Europa, one of Jupiter's moons. Researchers believe that polar ice caps there could harbor a hidden ocean. If this idea pans out, NASA will have Grant Gilmore and his fascination with the sounds of fish to thank. For Living on Earth, I'm Angela Swafford on Mosquito Lagoon.
CURWOOD: Thanks to Esther San Pedro for her help with the underwater recordings used in our story.
(Music up and under: S. Rawcliff "Aquanots")
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