Great white shark numbers are surging, study says
FILE - In this undated file publicity image provided by Discovery Channel, a great white shark swims near Guadalupe Island off the coast of Mexico. The Discovery network special âMegalodon: The Monster Shark Lives,â opened Discoveryâs annual âShark Weekâ on Sunday, Aug. 4, 2013. With an estimated 4.8 million viewers, it had the largest audience of any show in the 26 years that Discovery has made âShark Weekâ a part of its summer programming, the Nielsen company said. (AP Photo/Discovery Channel, Andrew Brandy Casagrande, File)
This undated publicity image released by Discovery Channel shows a great white shark off the coast of New Zealand. Shark Week begins Sunday, Aug. 4 at 9 p.m. EST on Discovery. (AP Photo/Discovery Channel, Jeff Kurr)
A nine foot great white shark swims beneath the harpoon boat, Ezyduzit, off of the eastern point of South Monomoy in Chatham, Mass on Saturday, July 31 2010. After a spotter plane saw the great white swimming near South Beach Friday, officials closed the eastern shore of the beach to swimming for the weekend. The swimming closure stretches from south of Lighthouse Beach to Monomoy Island. (AP Photo,Wendy Maeda, Pool)
FILE - In this undated photo provided by the University of California, Davis, a white shark investigates a fake seal decoy used by UC Davis researchers in the Pacific Ocean near San Francisco. They are the most feared predator in the ocean, but the state of California thinks great white sharks might need a little protecting of their own. On Wednesday, Feb. 6, 2013, the Fish and Game Commission will consider advancing the candidacy of the giant sharks to the California Endangered Species list. (AP Photo/University of California, Davis, file)
Great white sharks swim around the boat during a shark festival in Gansbaai, South Africa, Saturday, Aug. 18, 2007. The self-proclaimed Great White Capital of the world hosted a weekend festival to dispel the myths and misconceptions that have plagued the shark since the film "Jaws" which portrayed the mighty predator as an indiscriminate killing machine. (AP Photo/Obed Zilwa)
Brian Anderson, right, of Seaside, Ore., describes how a great white shark held his leg, to his son Christian Anderson, 10, as he lays in the trauma unit of a hospital in Portland, Ore., Monday, Dec. 26, 2005. Anderson beat off the shark attack on Saturday, Dec. 24, as he surfed off Tillamook Head on the Oregon Coast. (AP Photo/Greg Wahl-Stephens)
CHATHAM, MA - AUGUST 11: A seal swims in the water near a Cape Cod pier on August 11, 2012 in Chatham, Massachusetts. A man was confirmed to have been bitten by a great white shark less than two weeks ago along the shoreline at Cape Cod. An increase in the seal population on Cape Cod has led to increased shark sightings near the shore, including great whites. (Photo by Mario Tama/Getty Images)
TRURO, MA - AUGUST 12: A colony of several hundred seals sit on a sandbar at High Head Beach during low tide on Cape Cod on August 12, 2012 in Truro, Massachusetts. A man was confirmed to have been bitten by a great white shark less than two weeks ago in the ocean near the shoreline of Truro in Cape Cod. An increase in the seal population on Cape Cod has led to increased shark sightings including great whites. (Photo by Mario Tama/Getty Images)
PORTLAND, Maine (AP) - A report that scientists are calling one of the most comprehensive studies of great white sharks finds their numbers are surging in the ocean off the Eastern U.S. and Canada after decades of decline - bad news if you're a seal, but something experts say shouldn't instill fear in beachgoers this summer.
The study by the National Oceanic and Atmospheric Administration, published this month in the journal PLOS ONE, says the population of the notoriously elusive fish has climbed since about 2000 in the western North Atlantic.
The scientists behind the study attribute the resurgence to conservation efforts, such as a federal 1997 act that prevented hunting of great whites, and greater availability of prey. The species is listed as vulnerable by the International Union for Conservation of Nature.
"The species appears to be recovering," said Cami McCandless, one of the authors. "This tells us the management tools appear to be working."
Great whites owe much of their fearsome reputation to the movie "Jaws," which was released 39 years ago Friday. But confrontations 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.
They are, though, ecologically critical. They are apex predators - those at the top of the food chain - and help control the populations of other species. That would include the gray seal, whose growing colonies off Massachusetts have provided food.
"You should be concerned for a good reason," said James Sulikowski, a professor of marine science at the University of New England in Portland, who was not involved in the study but noted it could help better target future conservation efforts for great whites. "We need these sharks in our waters."
A separate study published in PLOS ONE this month suggested that great whites - also known just as white sharks - are also returning to abundance in the eastern north Pacific Ocean.
"There's this general pattern of where the white sharks are protected, they seem to recover," said Tobey H. Curtis, one of the authors of the Atlantic study.
The elusive nature of white sharks and the lack of historical data about their population levels required the authors to rely on sightings of sharks, as opposed to other ways to count sea life, such as commercial fishing surveys and census counts, Curtis said.
The research adds recent unpublished data to previously published records to establish 649 confirmed white shark sightings from 1800 to 2010. The data show that a period of decline in white shark abundance during the 1970s and 1980s has reversed, the authors said.
White shark abundance in the western North Atlantic declined by an estimated 73 percent from the early 1960s to the 1980s, the report says. Shark abundance is now only 31 percent down from its historical high estimate in 1961, the report states. The report does not provide a local estimate for the great white shark population, which some scientists say is between 3,000 and 5,000 animals.
The report also illuminates where people encounter white sharks - mostly between Massachusetts and New Jersey during the summer and off Florida in the winter, it says.
They also migrate based on water temperature and availability of prey, and are more common along the coast than offshore, the report states.