CHATHAM, Mass. » Great white sharks are having an unusual effect on Cape Cod this summer, and many a merchant is going to need a bigger wallet.

The sharks being spotted in growing numbers are stirring curiosity and a buying frenzy for shark-related merchandise.

Shark T-shirts are everywhere, "Jaws" has been playing in local movie theaters and boats are taking more tourists out to see the huge seal population that keeps the sharks coming. Harbormasters have issued warnings, but — unlike the sharks in the movies — the great whites generally are not seen as a threat to human swimmers.

Among the entrepreneurs is Justin Labdon, owner of the Cape Cod Beach Chair Co., who started selling "Chatham Whites" T-shirts after customers who were renting paddleboards and kayaks began asking whether it was safe to go to sea.

"I mean, truthfully, we’ve probably grown about 500 percent in terms of the sale of our shark apparel," he said. The T-shirts, hoodies, hats, belts, dog collars and other accessories bear the iconic, torpedo-shaped image of great whites and sell for between $10 and $45.

He said his store brings in thousands of dollars in sales of the shark-themed merchandise.

Tourists peer through coin-operated binoculars in hopes of catching a glimpse of a shark fin from the beaches of Chatham. The posh resort town is on the elbow of the cape that has a large population of gray seals — the massive animals whose blubber is the fuel of choice for great white sharks. Local shops sell jewelry, candy, clothes, stuffed animals and beverages with shark motifs.

A study released last month by scientists at the National Oceanic and Atmospheric Administration found the number of great white sharks off the Eastern U.S. and Canada is surging after decades of decline. Conservation efforts and the greater availability of prey such as Massachusetts’ seals are credited with the reversal.

Shark sightings have soared from generally fewer than two annually before 2004 to more than 20 in each of the last few years off Cape Cod, where the economy depends heavily on the summer tourism season. Despite notices urging boaters and swimmers to use caution, the official reaction has been nearly the opposite of the panic depicted in "Jaws," the 1975 film shot mainly on the Massachusetts island of Martha’s Vineyard.

"White sharks are this iconic species in society, and it draws amazing amounts of attention," said Greg­ory Sko­mal, a senior marine fisheries biologist who also leads the Massachusetts Shark Research Program, who said people are coming in hopes of witnessing the animals in their splendor. "I have not been approached by anyone who has said to me, ‘Let’s go kill these sharks.’"

Skomal said sharks have been coming closer to shore to feed on the seals, which he said have been coming on shore in greater numbers because of successful conservation efforts.

Confrontations with people are rare, with only 106 unprovoked white shark attacks — 13 of them fatal — in U.S. waters since 1916, according to data provided by the University of Florida.

Still, officials are wary of the damage that could be done to tourism if one of the predators bites a person. Brochures have been distributed to raise awareness of sharks and safe practices in the event of a sighting.

"You have to make sure people understand," Cape Cod Chamber of Commerce CEO Wendy Northcross said, "if they go to the beach and they see a family of seals there, that’s probably not the best place to hang out."

Laurie Moss McCandless of Memphis, Tenn., has vacationed on Cape Cod every summer since she was a little girl and doesn’t remember hearing about sharks back then. But her son is obsessed with sharks, she said, and she’s hoping to hear more about them on their vacation in Chatham.

"He loves all his sharks paraphernalia," McCandless, 39, said as she bought a shark-themed sweatshirt for one of her three children.