Gathering by the shores of Monomoy Island near Martha's Vineyard, where much of the movie "Jaws" was filmed, great white sharks have people on notice in the Northeast.
The sharks make a pilgrimage to this region every year to feed, but a particularly large gray seal population has become an enticing magnet for the large, toothy predators. The presence of the sharks has created a booming tourism business as well as some jitters in the area.
"Gray seals have a lot of blubber and meat, so they are a high efficiency preferred menu item of great white sharks," New England Aquarium spokesperson Tony LaCasse told Discovery News. "Somehow the word is out in the great white world that this is the place to be."
He added, "Humans are not on their menu because we are a completely inefficient meal, since great white sharks are looking for maximum calories per kill."
Federal protection of marine mammals has been in place since 1972, and has led to the recovery of gray seals in the area, which are larger and fattier than Harbor seals that are in the waters off of Cape Cod. LaCasse suspects it took this long for gray seals to build up their population.
When seal numbers were down, the great white sharks mostly fed on dead whale carcasses, called "floaters." LaCasse said just this May, a fisherman went to explore a dead Minke whale near Martha's Vineyard and was surprised by a great white shark that swam out from under the whale "and checked him out.” The fisherman escaped without injuries.
Monomoy Island, where the great whites have been spotted, is an 8-mile spit of sand extending southwest from Cape Cod, and a national wildlife refuge, where access is limited. This has helped to keep people safe from the sharks. A booming tourism industry, with great white sharks as the No. 1 draw, has emerged in nearby Chatham, Mass. Tourism dollars are down by 4 percent in the Cape as a whole, but Chatham has seen a 15 percent uptick, especially now that it's the summer vacation season. LaCasse said during one recent tour, "a great white took a free-swimming seal" in a bloody, violent battle viewed by families riveted to the real life event.
Recent research supports the rise in great white shark numbers off of Cape Cod. A tagging project led by Greg Skomal of the Massachusetts Division of Marine Fisheries (DMF), succeeded in tagging six white sharks, ranging from 10 to 18 feet in length, off the coast of Monomoy Island. The DMF notes there has been a "recent increase in shark sightings," mentioning "the growing population of gray seals."
Not everyone appears to be pleased by the changes. In the past several weeks, five adult gray seals were found shot on Cape Cod beaches from Dennis to Chatham. Some local fishermen have expressed concern over the seals' presence, which has decreased the prevalence of certain fish. It remains unclear, however, who shot the seals.
No shark attacks have been reported off of Massachusetts this year, according to Bethan Gillett, a technician at the International Shark Attack File at the Florida Museum of Natural History.
She did indicate there's been a modest rise in attacks nationwide since May, with seven happening that month, seven reported in June, and three occurring in July so far.
"I don't think we are seeing a spike in attacks, though," Gillett told Discovery News. "The attacks are correlated with more people in the water for recreational activities."
One shark victim was a 12-year-old boy who was bitten in the foot by a bull shark off the Texas Gulf coast. The boy has endured several surgeries and requires more, but he is expected to make a full recovery.
"This was very unusual for Texas," Mike Cox, a spokesperson for the Texas Parks and Wildlife Department, told Discovery News. "We haven't had a fatality due to shark attack since 1962, so no one feels this is cause for panic or alarm. You are more likely to be hit by lightning than to be bitten by a shark."
LaCasse pointed out that bull sharks can be particularly tenacious, since they have the highest measured testosterone of any animal. To avoid encountering one, or any shark, he advises, "If you see a seal in the water, you should not be in the water. We're poor swimmers, and when sharks see us thrashing around, they can confuse us for their desired prey."
He also advises not to swim alone in deep water and not to swim at dusk, when visibility is down and shark numbers might be up.