Fish researcher eavesdrops on Barry Whites of the deep
By Associated Press
Published May 10, 2004
WABASSO - It's spring, the moon is full and love is in the air - and under water: Inches below the quiet surface of the Indian River Lagoon, passion is boiling. And fish expert Grant Gilmore is eavesdropping.
Armed with a hydrophone and a tape recorder, he's listening to fish mating calls. He's hoping to hear lots of noise, an indicator that breeding is up and the population is healthy. A few feet below his boat, the females wait silently, listening for the male with the strongest voice.
"The males are trying to impress the females," Gilmore said. "All those little squeaks and grunts mean something."
It is well known that whales and dolphins talk to each other under water and that sea turtles travel thousands of miles to nest on the same Central Florida beach. Frogs and birds attract each other with their songs.
Less well known is that even the tiny six-inch yellowtail, or spotted sea trout, or huge black drum call out to their mates and spawn the same place year after year.
For a quarter century, Gilmore has been keeping track of where they breed. Indians and Chinese have located spawning grounds of larger fish for centuries by listening to their sounds through the bottoms of canoes and sampans.
There are 15 to 20 spawning areas in the 157-mile-long Indian River Lagoon, an estuary that stretches from Palm Beach County north to Volusia County. Some spawning sites are as small as 100 yards square. The largest is 100 yards wide by nearly a mile long.
Males by the thousands come from miles around to nature's submarine nightclub. But only one in five females show on a given night.
Homing in on a sound that erupts from the male's gas bladder, the female swims to the most potent sound producer. She beckons him to follow her. Sometimes other males tag along. They rocket toward the surface.
On a dark night their speed produces a bright blue luminescent trail in the inky water. Just before they crash through the surface, the female ejects thousands of eggs and the male releases his sperm. Each egg contains a tiny droplet of oil that helps it float for 24 to 48 hours until the embryo hatches and eventually heads to the safety of sea grasses below.
On this night, Steve Van Meter, a NASA robotics expert, is piloting the 19-foot shallow water boat that Gilmore, 57, is using for his research. NASA, through Dynamac Inc., is one of many organizations that have sponsored Gilmore's work.
During a recent trip in the lagoon, Van Meter's boat drifted over a small but active spawning ground, causing speakers on Gilmore's boom box to erupt with sound. "They are having a big party tonight," Gilmore said, laughing.
"The main things you hear are the silver perch, that little "dit-dit-dit-dit.' There's a toad fish. It makes that sound like a fog horn," Gilmore said. "That sound there - like someone knocking on a door - that's the hard-head catfish, or sea catfish." Off in the distance comes the soft "muhroooo, muhroooo" of several topsail catfish.
Then, a surprise. A low, booming sound, like "WHA-UMP!" A black drum. Maybe 100 pounds and three feet long. The black drum is the only species in which the female talks back to the male.
As the boat drifts eastward the symphony takes on a sizzle. Tiny shrimp call to each other in a sound like frying bacon. By the end of a two-hour session, Gilmore has cataloged five species of fish and heads back to the dock.
Besides the ecological benefits, Gilmore said, a good fish population is critical to South Florida's multimillion-dollar sport fishing and tourism industry.
Over the past 25 years, spawning has declined in the lower quarter of the lagoon, stayed about the same from Stuart north through Cocoa Beach, and grown in the north, where the lagoon is widest and farthest from city lights. Where water quality drops, or where salinity goes down, spawning decreases.
If by now you're headed toward the garage to oil up your rusty reel, back off. Gilmore would sooner cut off his right arm than give up the location of most of these sites. One he will talk about is deep in the Mosquito Lagoon near the launch pads at the Kennedy Space Center.
By virtue of being next door to one of the most secure places in North America, these fish are protected 24-7 by a SWAT team.
