A factor in shark attack increase: More people in water

Federal wildlife protections are helping sharks rebound, but they aren't the sole reason for the uptick in encounters between sharks and humans. Expanding human populations and growing use of beaches are major factors too, scientists say.

Recent shark attacks in North Carolina and Florida have made headlines as the summer beach-going season gets into gear. Such attacks have become more common in recent years—the Florida Museum of Natural History's International Shark Attack File says the number of unprovoked shark attacks has grown in every decade since the 1970s.

Shark researcher George Burgess, who publishes the file, said this decade is almost certain to set a record for shark attacks.

"The fact of the matter is, while shark populations rebound and hopefully come to where they once were, the human population is rising every year," Burgess said. "We're not rebounding, we're just bounding."

Americans made 2.2 billion visits to beaches in 2010, up from 2 billion in 2001, according to a U.S. Army Corps of Engineers estimate. A spokesman for the American Shore and Beach Preservation Association said the figure is likely still rising because of the improving economy.

Populations of some shark species have grown due in part to conservation efforts, such as a 1997 U.S. law that prevented the hunting of great white sharks. Dr. Bob Hueter, director of the Center for Shark Research at Mote Marine Laboratory & Aquarium in Sarasota, Florida, said preservation and management have also helped repair populations of species like the sandbar shark and blacktip shark.

The Marine Mammal Protection Act of 1972 also has helped increase the population of seals, which are a favorite prey of white sharks. In Massachusetts, the growing number of seals has raised concerns in recent years about the animals attracting sharks to beaches favored by humans.

Hueter said the rebounding white shark population justifies vigilance, but he added that it's presumptive to assume there are more shark attacks because there are more sharks in the ocean.

"Sharks are fairly sophisticated. If they are hunting for seals, they are going to concentrate their efforts near a seal colony," he said. "Are you going to go swimming in a seal colony? Of course not."

There were 72 shark attacks worldwide in 2014, three of them fatal, according to the International Shark Attack File. The deadliest recent year was 2011, when 13 of 79 attacks were fatal.

Greg Skomal, senior scientist with the Massachusetts Division of Marine Fisheries, said encounters with marine animals such as sharks are inevitable as long people keep visiting their habitat.

"If shark populations do return to historic highs, then you know there will be the issue of coexistence, because the one trend we do see is more and more people going to the shoreline," he said.

© 2015 The Associated Press. All rights reserved.