While legend records that Nero fiddled as Rome burned, University of South Florida College of Marine Science biological oceanographers David Mann and James Locascio have documented that during Hurricane Charley, fish in Charlotte Harbor that normally sing “love songs” while spawning sang their hearts out, and louder than ever during the storm. The scientists, who regularly eavesdrop on the unique sounds fish make during spawning, went back to their recorded data after Charley’s fury and found the hurricane did not inhibit the nightly chorus of singing, love-struck fish. Fish sound levels on the evening of Charley - and for three days thereafter - were higher than the days prior to the storm.
“When Hurricane Charley passed directly over Charlotte Harbor with 140 mph winds, we had a unique opportunity to document both the acoustic energy of the storm and to find out if the storm had an effect on the calling behavior of fish,” said Mann.
According to Mann and Locascio, many male fish produce specific courtship sounds. They have identified species-specific sounds using 10 hydrophones from the Long-Term Acoustic Recording System (LARS). LARS, custom built at CMS, uses a system of recording devices anchored just off the bottom of the shallow waters of Charlotte Harbor. The hydrophones record underwater sounds for ten seconds every 10 minutes for up to 50 days.
“The loudest low frequency sound from the storm sounds were recorded at 4 p.m. when Charley’s eye was in the mouth of Charlotte Harbor,” said Locascio, adding they had expected the fish love songs to shut down during the storm. “Sound from the hurricane was minimal an hour and a half later, at which time the first fish calls were recorded.”
They recorded the hurricane’s low frequency noise from zero to 100 hertz (Hz) while the higher pitched fish spawning songs were recorded at 500-600 Hz. Their data, recorded for three nights after the hurricane, showed an increase in fish calling with maximized sound levels and a start time more than two hours earlier than nights prior to the storm.
“We found no immediate negative storm impact on chorusing fish populations,” explained Mann. “It is possible increased fresh water flow into the harbor from hurricane rains could impair chorusing and spawning.”
Among the recordings were the sand sea trout’s unique call, which typically begins its courtship calls about dusk and ends a few hours later and sounds like a “double-pulse” purring while the fury of Charley sounded like a dull “shhhhhhh.” They used the sounds to generate a visual “spectogram” of the data.
“Nightly chorusing events started at about 7:30 p.m. and lasted nearly seven hours,” said Locascio.
Mann and Locascio recently presented the data recorded during Hurricane Charley at a conference at the Mote Marine Laboratory in Sarasota.
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