National Geographic : 2016 Jun
swimming with tigers 97 called Shark Bay, a research team led by Mike Heithaus of Florida International University has documented how tiger sharks prevent sea turtles and dugongs (sea cows) from overgrazing the sea grass beds that anchor the ecosystem. It’s not just by eating the animals, researchers discovered. The mere presence of the sharks changes the tur- tles’ and dugongs’ habits, creating a “landscape of fear” that forces them to graze more judiciously in order to lessen their risk of being eaten. What this means is that protecting animals like sea turtles without also protecting the pred- ators that keep them in check could lead to de- graded ocean ecosystems. “If you look at places where shark populations have declined and turtle populations are protected—places like Bermuda—it looks like those areas are having losses in their sea grass,” Heithaus says. In the Bahamas, which prohibited longline fishing in 1993 and designated its waters a shark sanctuary in 2011, the marine ecosystems are rel- atively healthy. But the adjacent western Atlan- tic, which includes Bermuda, has much weaker shark protections and appears to be suffering the consequences. Neil Hammerschlag, a marine ecologist at the University of Miami who stud- ies tiger sharks in the western Atlantic, says sea turtles there don’t seem to alter their behavior in response to tiger sharks the way the turtles in Shark Bay do, and that might be because At- lantic tiger shark populations are already sig- nificantly compromised. “I do work in Florida and the Bahamas, and it’s night and day. We see massive differences in the size and numbers of the sharks. They’re doing well in the Bahamas, but we almost never catch them off Florida. And they’re just 50 miles apart.” Florida prohibited the killing of tiger sharks in its waters in 2012, but it’s the only state on the eastern seaboard to have done so, and federal law allows them to be caught and killed in U.S. waters, within certain limits, by commercial and recreational fishermen. JAW S ISN’T RESPONSIBLE for most of the threats tiger sharks face—coastal development, ma- rine pollution, longline fishing, the popularity of shark fin soup—but it did create a cultural attitude that has had a remarkably long shelf life. After Jaws, people didn’t just become paranoid about sharks; they became callous, even vengeful. In the 1970s and ’80s, shark- fishing tournaments sprouted like weeds on the eastern seaboard of the U.S., and dozens of them continue, celebrating the spectacle of “monster sharks” hanging on the docks. I went to one of these tournaments last summer, and the mem- ory that sticks is of a woman with her little boy, pointing at a mako with its bloody jaws propped open for the cameras and saying, as if to prompt him to follow suit, “Oooh, scary!” Sharks can be scary, that’s true. But I spent a couple of days on Kauai with Mike Coots, a photographer who lost half his right leg to a ti- ger shark while bodyboarding in 1997, when he was 18. He was soon back in the water and says he almost never thinks about sharks when he’s surfing. “Hawaii is an ocean culture,” he told me. “People here are in the water from the time they’re in diapers. They’re just not that afraid of sharks.” To test that, I asked the boys playing four square in front of his house whether they were afraid of sharks, and they said, “No,” like it was the stupidest question they’d ever heard. They were about the age I was when I saw Jaws. Last summer, as I was planning my dive at Tiger Beach and hysteria about recent shark at- tacks in North Carolina was in full bloom, news broke that an 800-pound tiger shark had been caught off the South Carolina coast. USA Today called the shark “monstrous” and described the fishermen as “brave souls.” When I got home from Hawaii, I looked at the story again. Seeing the picture of the gutted, deflated shark on the dock, I thought about how it was once the same size as Sophie, and those weren’t at all the words that came to mind—for either the shark, or the men who killed it. j Go underwater with photographer Brian Skerry to see video of tiger sharks in action at ngm.com/ Jun2016 and get a close-up look at how he captures images like the ones shown here.