Friday, April 11, 2008

Noisy Fish

The International Herald Tribune reported Wednesday on a little-known phenomenon: Fish can get downright noisy.

It was the end of January 2005, during the spawning season for a fish appropriately called the black drum. Nightly mating calls were at a crescendo. But no one living in the area seemed to realize the din was of aquatic origin.

The retirees who had come to spend their winters relaxing on the gentle estuaries and canals of the Gulf Coast in Florida blamed the municipal utility system. They were pushing the City Council to pay an engineering firm more than $47,000 to eliminate the noise reverberating through their homes.

Then James Locascio, a doctoral student in marine science at the University of South Florida, rescued the city from financial folly. After reading the newspaper article, Locascio called a Council member just hours before a vote to appropriate the money. He explained that at 100 to 500 hertz, black drum mating calls travel at a low enough frequency and long enough wavelength to carry through sea walls, into the ground and through the construction of waterfront homes like the throbbing beat in a passing car.

Many residents didn't believe him, and why should they? Hadn't Jacques Cousteau called the oceans, "The Silent World"?

Locascio and David Mann, a marine biologist at the University of South Florida who is a bioacoustics expert, recruited these naysayers into a study by asking them to score noise levels and times in notebooks. "We took their data and plotted them with the fish sounds we had recorded with hydrophones under the water," Locascio said. "Concordance was perfect."

Other people in different places have been mocked when they reported hearing fish sounds, but the mockers are the mistaken ones.

Yet of the 30,000 species out there, only about 1,200 sound producers have been catalogued, and far fewer have been recorded. Even common goldfish have merited just two scientific publications. In fact, said Philip Lobel, a professor of biology at Boston University, "Most aquarium fish are sonic. Keeping fish in an aquarium is like keeping a canary in a soundproof cage."

If you have fish in an aquarium, don't let the PETA people find out.

It surprises me, though, when I learn that most people don't know something I already know, because for most things in life, I'm the last to find out. But this is one of those rare cases (OK, I didn't know about the goldfish).

My dad was a radioman in the Navy on several submarines. When I was a kid, he told me (maybe all three of us) that he had to learn which underwater noises were natural and which ones were man-made. He said that shrimp sounded like very loud castanets. I've remembered that ever since, because I know what castanets sound like.

There's a link in the IHT article (under the "Multimedia" heading on the left) that lets you listen to several kinds of fish, including Florida's nemesis, the black drum fish. No shrimp, though. I checked.

No comments: