August 2, 2012 — The white shark state officials believe bit a man swimming off Truro Monday was likely looking for a more blubbery victim. A burgeoning seal population has drawn the fearsome fish closer to Cape Cod's shores, primarily off Monomoy Island in Chatham.
But both the seals and the sharks that eat them are far from stationary. Gray seals use several areas around the Cape and Islands as haul-outs, where they rest and mate, or rookeries, where they give birth to their pups.
"The seal population on Cape Cod is quite dynamic," said Brian Sharp, stranding coordinator for the International Fund for Animal Welfare headquartered in Yarmouthport.
There are three primary haul-outs on the Cape: Monomoy National Wildlife Refuge; sand bars on the ocean side of North Truro; and Jeremy Point, a peninsula of land that hangs like a stalactite from Wellfleet's Great Island into Cape Cod Bay.
Muskeget Island west of Nantucket is home to the largest pupping colony of gray seals on the East Coast with 2,095 pups counted during the 2007 and 2008 season.
The largest Cape haul-out on Monomoy hosts thousands of seals and has also been used as a pupping site, according to Sharp and other marine mammal experts.
But gray seals, which can grow to six feet and 400 to 800 pounds, can be found on beaches throughout the region, Sharp said.
Seal populations in the United States were decimated during a long-standing bounty program and prior to the passage of the Marine Mammal Protection Act in 1972. Since then, seals from Canada, including a large rookery on Sable Island more than 100 miles off Nova Scotia, have reinvigorated the population of seals in the U.S.
In the 1970s there were only about 500 seals in the waters around the Cape, said naturalist Dennis Murley with the Massachusetts Audubon Society's Wellfleet Bay Wildlife Sanctuary. That number could now be 10,000 to 15,000, he said.
On Jeremy Point, the increase was coupled with a shift in species from a population dominated by harbor seals to one now made up primarily of gray seals depending on the time of year, Murley said.
There are three basic conditions that make a location more ideal for seal haul-outs, seal experts said.
The first is easy access to deep water.
Because the tide recedes so far on cup-shaped Cape Cod Bay, seals are unlikely to set up shop on beaches deep inside it, Murley said. Second, seals need an abundant food source. Here, that includes sand eels and fish. Many local fishermen complain seals have decimated the striped bass population but wildlife experts say that's not true.
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