Swimming with the sharks is a popular tourist activity in places like Tiger Beach in the Bahamas. While courageous vacationers enjoy being so close to such powerful animals, scientists wonder whether attracting the sharks with an abundance of food is having a negative impact on the environment.

Sharks, which LiveScience.com's Andrea Mustain called "the Godfathers of the ecosystem," make sure that populations in line so that the ocean stays balanced. The fear is that sharks that have easy access to a generous food supply would not swim as far in the ocean, and this would disrupt the equilibrium of the oceanic environment. Not only would the population changes be harmful to aquatic life, but having the fish make an association between people and food could also be dangerous to humans. Shark attacks are rare, but they might become more common if sharks make such a connection.

Yet despite these concerns, there is evidence that ecotourism could be beneficial to sharks. "In the Bahamas, they've encouraged shark diving because it's good for the economy, and because of that they're protecting sharks in their water," said Neil Hammerschlag, an assistant professor at the University of Miami.

The university's website reports that a study that Hammershclog conducted last year showed that shark-dive tourism generates more money to local economy than shark finning, which kills the sharks so that the fins could be used in a delicacy known as shark fin soup.

Shark attacks are hard to track because of their rarity, so it will be difficult to discover if sharks learn to think of humans as a food source. Their movements and hunting patters, however, are easier to measure and study. Hammerschlog and his colleagues put satellite tags on the dorsal fins of tiger sharks from the Bahamas and Florida.

In the Bahamas, ecotourism encourages people to feed sharks, and Florida doesn't allow it. Scientists observed that the sharks did not behave as they expected."In fact, we found the opposite," Hammerschlog said. "The tiger sharks from the Bahamas diving site moved massive distances."

Hammerschlog explained that while the sharks knew the tourisms sites were grounds for food, they did not rely only on those places. Instead, some sharks swam over 2,000 miles away from shore, an area five times greater than the tiger sharks in Florida.

"These apparent feeding forays follow the Gulf Stream, an area of high biological productivity that concentrates shark prey," said Jerald S. Ault, professor of marine biology and fisheries at the University of Miami.

As a result of these studies, the researchers are advising not to discontinue tourist attractions like shark diving. They acknowledge, however, that more studies are needed.