The proposal for the ban came from a group of scientists and environmentalists clustered around University of Miami professor Samuel Gruber, the world's foremost lemon shark expert.

They fear that restrictions on catching other shark species over the past couple of years are leading fishermen to turn their attention to lemon sharks. Since 2004, the Florida lemon shark catch has risen more than 400 percent.

In the 1980s in the Florida Keys, for example, where Gruber was tagging sharks, the entire population had virtually disappeared by 1986.

Adding to the lemon shark's vulnerability is the species' bizarre habit of assembling in large, stationary groups on the ocean floor. A couple of miles off Jupiter, for example, lies the biggest known aggregation of lemon sharks, with groups of up to 100 visible during the winter.

The sharks play an important role in maintaining the health of shallow ecosystems, such as coral reefs, by preventing lesser predators from multiplying out of control, Gruber said. They hold down the population of stingrays, for example. Without this service, the stingrays would devastate the lobsters, with further consequences down the food chain.

"The lemon shark is one of the largest predators on the reef," Gruber said. "If you were to take away the predator pressure, you will cause an ecological disruption in the balance of species."