posted November 13, 2004 03:21 AM         

People experience waves from Hurricane Charley at St, Pete Beach, Fla., this summer. Beneath the waters, a study shows certain fish were singing and spawning. (Tim Boyles/Getty Images)

Nov. 10, 2004 — Not even the fury of Hurricane Charley could silence the amorous songs of fish that sang their hearts out shortly after 140 mph winds whipped up the waters of Florida's Charlotte Harbor last August.

Scientists who have been studying the mating sounds of fish there for several years had expected their recording tapes to reveal little reproductive activity on the evening of the hurricane. But it was business as usual for the fish, regardless of the nasty conditions.

"We were very surprised," says David Mann, a biological oceanographer at the University of South Florida's College of Marine Science.

Mann and colleague James Locascio have 10 hydrophones anchored just off the bottom of the shallow waters of Charlotte Harbor, which is south of Tampa Bay. So little is known about fish behavior during spawning that the scientists didn't know really what to expect when they installed the system.

What they got, they say, is songs. At least to a marine biologist the fish sound like they are singing while trying to get in the reproductive mood.

To the rest of us, Mann says, the "chorus," as it is called, would sound more like "humming, or grunting."

In the Mood

The target of all this attention is the sand sea trout, which really isn't in the trout family at all.

"It's in the croaker and drum family," Mann says, referring to common species that are familiar to just about any East Coast angler.

Scientists have known for some time that some fish are very audible during spawning. Some actually get their popular names from the sounds they make.

"That's why we have fishes with names like toad fish and pig fish, and croakers and drums," Mann says, because that's what they sound like.

So the thought occurred to Mann and Locascio that they might be able to learn more about the spawning habits of various fish if they listened to what they have to say.

"Spawning is probably the least understood thing in fisheries management," Mann says, and that's significant because if we don't understand how, when and where fish spawn, our impact on their environment could have catastrophic consequences. It turns out that the sand sea trout lays its eggs in the water column, not on the bottom, and they get carried off by the currents, so activities some distance from the spawning grounds could have a significant impact on the population of the species.

So the researchers were quite curious as to whether the fierce winds of Hurricane Charley interrupted the love life of the fish.

"The eye of the hurricane passed directly over our recording equipment," Mann says, and it really made a mess of everything.

"The harbor immediately after the hurricane was a very different place than it was the day before. All the mangroves had their leaves stripped off, and the water in the harbor was like chocolate milk there was so much sediment stirred up," he adds.

Focused Fish

The hurricane passed through about 4 p.m., an hour or so before the nightly courting begins in the harbor. The water is about 15 feet deep, so the powerful winds churned up the entire water column.

But it turns out that the fish couldn't have cared less.

"We have recordings of the hurricane sounds, and then like an hour or so later you hear the fish start calling, as they normally would, and that just builds into the nightly chorus," Mann says. "It sounds like a crowd in a stadium."

The researchers say the recordings sounded so normal that — except for the sounds of the hurricane — there was no way to tell that Charley had passed through.

"We had expected them not to spawn that night," Mann says.

But apparently the fish didn't see the churning waters as a threat, and they had something more important on their minds. And that led to what Mann admits sounds a little more like humming and grunting than the Top 40 list.

"It's sort of like what people do after a storm passes," Mann says. "You just keep doing what you were doing before."

He means singing, of course.

Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the "Los Angeles Times," he now lives in Juneau, Alaska.