The latest data from a multiyear study of the ocean predators found that the number of sharks in waters off the vacation haven appears to be on the rise, said Greg Skomal, a senior scientist with the Massachusetts Division of Marine Fisheries, and the state's top shark expert.
But that's no reason to cancel vacation. The sharks are after seals, not humans, and towns are using the information from the study to keep it that way.
"How long does it stay and where does it go are the questions we're trying to answer," Skomal said. "But for the towns, it's a public safety issue."
Researchers using a plane and boats spotted 147 individual white sharks last summer. That was up slightly from 2015, but significantly more than the 80 individual sharks spotted in 2014, the first year of the study , funded by the Atlantic White Shark Conservancy.
More than half the white sharks spotted last summer hadn't previously been documented by this study.
Researchers have also tagged more than 100 to track their movements.
The white shark population is probably significantly larger, because the scientists can't possibly spot all of them, Skomal said.
Two of the more interesting findings are the increasing number of young sharks, and that they appear to be swimming farther afield.
"Last summer we saw greater numbers of smaller sharks, including juveniles, and that tells us that the population is rebuilding," Skomal said.
Great whites, made famous in the 1975 movie "Jaws," about a monstrous shark that terrorizes a fictional New England resort town, are coming to Cape Cod waters to feast on seals. Once hunted to near extinction, the now-protected seals are found in great numbers.
The seals used to be concentrated at the Monomoy Wildlife Refuge, off limits to humans, but as they have moved farther north, so have the sharks, Skomal said.
The risk of a swimmer being attacked by a shark is minimal, and Cape Cod towns would like to keep it that way.
The last documented fatal great white shark attack in Massachusetts waters was in 1936, Skomal said. In 2012, a man bitten while swimming off Truro required 47 stitches and surgery to repair damaged tendons. In 2014, two young women kayaking off Plymouth were attacked, although neither was bitten.
Nathan Sears, the natural resources manager in Orleans, said the study is invaluable and is already prompting changes in how the town manages its beaches.
The town used to fly dangerous marine life flags - they have a picture of shark on them - only when they knew there was a shark in the area. Now, he said, they fly the flag every day during the tourist season.
"The fact that they have an eye on the situation from the air is crucial," he said. "And if they spot a shark in the swimming area, we'll close the beach."
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