PORTLAND – An unusually high number of dead seals have been found along Maine’s beaches in recent weeks, prompting an investigation by federal fisheries officials hoping to learn what caused the deaths.

The 27 dead harbor seals found Friday on Stratton Island off Prouts Neck were among nearly 300 dead and stranded seals reported to the Westbrook-based Marine Animal Lifeline in the past six weeks, which responds to seal strandings.

“As of the last week of June of this year, we started to notice a very large spike in stranding events,” said Greg Jakush, Marine Animal Lifeline founder. “Our numbers started doubling, tripling, quadrupling.”

The deaths were not isolated to Stratton Island, where Maine Audubon volunteers monitoring tern colonies found the dead seals, he said.

The surge in reports of dead seals prompted the National Marine Fisheries Service to declare an “unusual mortality event.” Officials also considered a smaller number of deaths last year an unusual event, spokeswoman Teri Frady said.

Although most dead seals that wash up on beaches are either sickly adults or pups, seals recently found dead appeared to have been healthy, Frady said.

Fisheries officials hope tests will determine what is causing their deaths.

It could be something in the environment, or a disease, Frady said. Several years ago, an unknown form of distemper killed thousands of seals in Europe.

“I don’t think anyone has a good solid theory at this point,” she said.

Volunteers in Maine were testing blood samples from living seals but have not found a potential cause, Jakush said. But unlike a rash of seal mutilations and deaths reported in late 2003 and early this year, human interaction is not believed to be a factor in the deaths.

Marine biologists in Maine will be keeping an eye on Stratton Island for more carcasses. The ones found there were several weeks old, and little could be determined from forensic examinations.

Jakush urged anyone who sees a dead or living seal on a Maine beach to call the lifeline.

“The quicker we can get to an animal, the fresher the samples are going to be and the more information it’s going to yield,” he said.

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