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Airdate: Nov 11, 2005
Scientist: Damon Gannon


The Atlantic Croaker might be a bit too noisy for its own good. why then, does it continue to sound off?

ambience: croakers "knocking."

Atlantic Croakers are saltwater fish that make a lot of noise. But sometimes their distinctive "knocking" calls put them in danger. I'm Jim Metzner and this is Pulse of the Planet. Scientist Damon Gannon studies Croakers at the Mote Marine Laboratory in Sarasota, Florida. He says that hungry bottlenose dolphins use the sounds produced by Croakers to find them and eat them.

"There is a paradox regarding why fish make these sounds if these sounds make them more susceptible to predation risk, and the reason varies from species to species. Many of these fish are making these sounds in association with spawning. They are perhaps spawning advertisements. This may be how males and females find each other, so if you don't make a sound, you don't reproduce, and if you don't reproduce, you lose in the evolutionary game. But in the case of croaker, some of these sounds at least are not made for the purposes of spawningI do believe that these are contact calls to help maintain the cohesiveness of a group of fish in murky waters."

The call of croakers and other creatures are not the only sounds penetrating these waters.

"we humans are now putting a lot more sound pollution into the water from boat traffic and coastal development and other things, and we have to think very carefully about how we are impacting their communication system. The sounds that we are making are within the same frequency range of the sounds that the fish are making. We might be disrupting their communication systems to communicate over long distances. "

Even though it's still a bit of a mystery as to why Croakers continue to croak when their calls attract predators, the more we understand about why these fish make the sounds they do can help us keep the ocean ecosystem stable in a time of increased human use of the oceans.
Pulse of the Planet is made possible by the National Science Foundation.