A Massachusetts marine biologist who examined a 13-foot great white shark carcass found ashore near the Rhode Island state line wasn't able to determine how the shark died, state officials said Sunday. 
 
 Researchers investigate the carcass of a great white shark that washed up in Westport, Mass., just over the state line from Little Compton, R.I., Saturday Sept. 1, 2012. A Massachusetts marine biologist... (Associated Press) 
 
 State biologist Greg Skomal performed a necropsy on the 1,500-pound male shark Saturday and found no signs of trauma. A fisherman discovered the carcass Saturday morning on a rocky shoreline in Westport, less than a half-mile from public beaches in Little Compton, R.I. 
 
 "They will have a difficult time, if at all, figuring out how he was killed," said Krista Selmi, a spokeswoman for the Massachusetts Division of Marine Fisheries. 
 
 Little Compton officials closed Goosewing and South Shore beaches after the shark was found. Both beaches reopened Sunday and police sent out a patrol boat to watch for other sharks. 
 
 Selmi said officials plan to leave the shark's body where it is. 
 
 "There's really no means to move an animal of that size," she said. 
 
 The shark appeared to have washed ashore Friday night, Selmi said. The carcass is below the high tide level, and officials hope the tide drags the shark back out to sea. 
 
 Shark sightings have been rare in the area. But further east, there have been numerous reports of sharks off Cape Cod. In July, a man was bitten on his legs by a great white shark while swimming off Ballston Beach in Truro, Mass. ||||| Shark sightings shut down Cape Cod beaches 
 
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 (CBS News) Beach goers in Cape Cod, Mass. found themselves with some unwanted company this Labor Day weekend. 
 
 Two sharks were spotted, prompting officials to raise the red flag, banning swimming at some of the areas most popular beaches. From South Beach in Chatham, to the northern tip of Nauset Beach in Orleans, shark sightings are keeping bathers out of the water. 
 
 One swimmer said, "Someone told me they can't come close to the edge, but I don't believe that anymore, so I'm just staying out." 
 
 The sightings aren't the first of the summer. In July, a man bodyboarding off Truro said he was bitten by a great white shark, the first known attack in those waters in over 75 years. He survived, but the incident led many to question why so many sharks are lurking off the cape. 
 
 Biologist and shark expert Simon Thorrold said the sharks are likely responding to an increased number of mammals - but not of the human variety. 
 
 "I think we're probably seeing more white sharks in the area at the moment," Thorrold said. "And the white sharks have probably been drawn into the area by a really large increase in the number of grey seals that are in the area." 
 
 That suspicion may have been confirmed this week when a family captured dramatic video of a shark attacking a seal off Monomoy Island. 
 
 Seals are a staple of a shark's diet. It is estimated 350,000 of them live along the North-Atlantic coast. They have been protected since the 1970s by the federal Marine Mammal Protection Act. 
 
 With the resident seal population showing no signs of slowing down, beach goers will have to share the shore with the sharks... at least until the great whites migrate to warmer waters this winter. 
 
 For Terrell Brown's full report, click on the video player above. ||||| Last Monday’s shark attack off Truro’s Ballston Beach – the first in 76 years on Cape Cod – set off a media furor and horrified beachgoers along the storied Massachusetts peninsula that attracts millions of vacationers every summer. 
 
 It may also force the hordes that crowd the Cape’s beaches to relearn a lesson lost for decades when seals had all but disappeared from the New England coasts – that swimming among shark’s prey is very dangerous. 
 
 Lifeguards were on high alert, hundreds of spurious dorsal fin sightings were reported and airborne spotters scanned the offshore swells for great white sharks, the prime suspect in the attack on Chris Myers, 50. 
 
 More than 300,000 grey seals, and their vulnerable pups, now live on the Cape – a population 30 times the nadir in the 1960s – and the return of the seals has attracted a return, inshore, of great white sharks. 
 
 “The reason the great white sharks are coming closer to shore in the Cape Cod area, specifically on the eastern shore, is because of the growing grey seal population,” said Greg Skomal, a Massachusetts marine biologist. 
 
 Mr. Myers and his 16-year-old son were swimming several hundred metres offshore, close to known seal colonies, when something bit his lower legs. 
 
 Meanwhile harried Massachusetts tourism officials were battling to prevent a single attack morphing into a nightmare marketing scenario of sinister fins slicing the waters off Cape Cod. 
 
 “Not to downplay the nasty experience the bitee has had but there are sharks in the ocean,” said Betsy Wall, executive director of the Massachusetts Office of Travel and Tourism. “There’s a lot of signs and notices about where it is safe to swim and where it is not. People should stay away from seals.” 
 
 Mr. Myers, 50, who is expected to make a full recovery from deep gashes that required more than 40 stitches to close, apparently got the message. 
 
 “Maybe people need to be a little more careful than I was,” he told Good Morning America, his lower legs still heavily bandaged. “Don’t be an easy meal.” 
 
 “It’s the summer news doldrums and nothing tops a shark attack for media excitement,” said George Burgess, director of the Florida Program for Shark Research who also maintains the International Shark Attack File at the University of Florida. “It’s a hot-button issue and not just because of the movie Jaws,” he said. 
 
 “When humans disregard the rules … such as going in the water with seals in the area,” there will be attacks, he said. 
 
 Great whites, while hardly the ferocious, man-eating terrors depicted in Steven Spielberg’s 1975 horror-thriller Jaws, are dangerous and have been sighted with greater frequency in recent years off Cape Cod as seal populations have re-established themselves. 
 
 Seals, along with sea birds, fish and dolphins are routinely eaten by the great white, which can exceed five metres in length and weigh more than two tonnes. 
 
 Seal-hunting sharks like to lurk just offshore to attack as the seals leave or return to the beach, especially where the bottom drops off suddenly, Mr. Burgess said. “It’s a bad idea to swim there.” 
 
 Shark attacks on humans are statistically rare; fatal attacks vanishingly so. In 2011, a typical year, just roughly 120 attacks were verified worldwide, of which only 17 were fatal. By comparison, an estimated 100 people die every year from jellyfish stings. The last, and unconfirmed, fatal shark attack in Canada was off Nova Scotia in August, 1891. 
 
 “But ultimately, the sharks are in their realm, … we are the intruders,” said Rob Mottice, a shark expert and marine biologist at the Tennessee Aquarium in Chattanooga, Tenn. “There will always be a handful of attacks,” he said. “Sharks attack because they mistake humans for something else. Whatever we do won’t change that.”
– A Labor Day disappointment on Cape Cod: Beaches have shut down along much of the coast thanks to shark trouble. Officials have banned swimming at several top sites after a pair of sightings, CBS News reports. The animals seem to be appearing more frequently lately; earlier this summer, a man was reportedly bitten by a great white off Truro for the first time in 75 years. "White sharks have probably been drawn into the area by a really large increase in the number of grey seals that are in the area," says an expert. And the sightings aren't limited to the Cape: A 1,500-pound shark turned up dead this weekend on the Massachusetts side of the Massachusetts-Rhode Island border. A biologist performed a necropsy, but officials aren't sure what killed the creature. They're going to leave it on the rocky shore, hoping the tide might eventually carry it out to sea: "There's really no means to move an animal of that size," a spokeswoman tells the AP.