THIS STORY HAS BEEN FORMATTED FOR EASY PRINTING

Cape Cod conditions may draw more great whites

Officials find no cause for alarm

By Patrick G. Lee
Globe Correspondent / June 29, 2010

E-mail this article

Invalid E-mail address
Invalid E-mail address

Sending your article

Your article has been sent.

Text size +

A growing population of seals off Cape Cod and rising water temperatures are combining to create conditions that could attract great white sharks to Cape beaches this summer, state and local authorities said yesterday.

The forecast followed Saturday’s sighting of a juvenile great white shark in Stellwagen Bank, between Cape Ann and Cape Cod. Still, officials said yesterday, there is no cause for alarm.

“We don’t believe it’s a threat to public safety,’’ Energy and Environmental Affairs Secretary Ian Bowles said. “People shouldn’t be saying they want to avoid the beaches or anything like that.’’

About a dozen shark species swim through New England waters every year, although great whites — made famous in the movie “Jaws’’ — garner the most attention.

The sharks can grow to 20 feet long and weigh in at more than 4,000 pounds, but, at odds with their Hollywood reputation, they are not usually man-eaters. Instead, the sharks tend to go mainly after seals and feed on dead whales.

The last death blamed on a great white shark in Massachusetts was in 1936.

The state’s top shark researcher, Gregory Skomal, yesterday disclosed a new finding about water temperatures for great white sharks that has prompted worries about more sharks being drawn to area waters.

In September, Skomal attached electronic tags to five great whites off Cape Cod to track their winter migration. Yesterday, Skomal said his preliminary analysis suggests that great whites spend most of their time in waters ranging from 59 to 67 degrees.

“That’s a really narrow temperature range for a fish,’’ he said. “That gives us a sense of where we can expect them to hang out and how long they hang out.’’

Jim Horna, Chatham’s marine operations supervisor, said the waters around Lighthouse Beach have warmed more rapidly this year and currently range from 58 to 64 degrees — right in the temperature span that great whites are known to like most.

Given the warmer waters and the growing gray seal population around nearby Monomoy Island, Chatham is becoming an increasingly attractive stomping ground for great whites, Horna said.

“It’s definitely a concern,’’ Horna said. “They’re hungry, seal is their main diet, and they’re coming in to have a nice meal.’’

Chatham closed five beaches on Labor Day weekend after great whites came near the Lighthouse Beach swimming area.

Skomal concurred that the rebounding seal population is most likely attracting traditional predators, including great whites, to feed on them closer to shore.

The population of gray seals in the western North Atlantic region has spiked dramatically, starting at less than 10,000 animals some two decades ago to more than 200,000 today, Skomal said. He attributed the “massive increase’’ to environmental protections of seals put into place starting in the early 1970s.

Besides Monomoy Island, other seal populations tend to hang around Muskeget Island off Nantucket and north of Head of the Meadow Beach on the Cape Cod National Seashore.

State officials said the decision to close beaches would remain up to individual municipalities. If they do shut them down, patrol boats and sometimes spotter planes will scan the waters.

Bowles encouraged beachgoers to use common sense while swimming, taking particular care to avoid splashing in waters near seal colonies.

But some areas with long stretches of unprotected beaches — those without lifeguards on duty — pose a greater risk to swimmers and surfers.

The Cape Cod National Seashore includes about 40 miles of coast with six beaches, of which less than 2 miles are guarded.

Some nearby towns also operate their own beaches in the area and provide lifeguards, but even so, the danger remains.

“We have never had a report of any white sharks at any of our protected beaches,’’ said Bob Grant, the National Seashore’s chief ranger. “But people can walk the beach for miles and miles and miles. . . . There needs to be an awareness that if those large seal populations are in the area, there possibly could be some other inherent dangers.’’

But no need for immediate concern — yet.

“A real good sign is when we have some seal carcasses washing up,’’ Horna said. “We’ll know ahead of time.’’

Patrick G. Lee can be reached at plee@globe.com.

Safety tips

State officials urge visitors and residents boating or swimming in Massachusetts coastal waters to follow simple precautions.

Follow local beach authority instructions about closings and beach staff commands and posted signs about closed swimming areas.

Notify the Division of Marine Fisheries about any great white shark sightings at 508-693-4372.

Never swim alone.

Avoid swimming in close proximity to large seal populations.

Avoid swimming at dawn and dusk.

Globe Staff

Connect with Boston.com

Twitter Follow us on @BostonUpdate, other Twitter accounts