Dead whale, more than 50 feet long, found in Boston Harbor

By Jaclyn Reiss and Matt Rocheleau, Globe Correspondents

A dead finback whale more than 50 feet in length was found floating in Boston Harbor early Sunday morning — a rarity for the area, officials said.

Tony LaCasse, a spokesman for the New England Aquarium, which sent officials to examine the whale, said how the massive mammal died remains a mystery.

“We don’t know,” he said. “We’ve only been able to look at a small portion of the body so far.”

LaCasse said the animal likely died because of one of three scenarios: natural causes, disease, or a unique medical problem, such as being struck by a vessel or becoming entangled in netting.

He said a large amount of blood in the water surrounding the whale and marks on its body may indicate trauma. But he added that it is unclear whether the possible trauma took place before or after the animal died.

Authorities did not know how old the whale was, but are conducting tests on samples taken from the animal, and planned to perform a necropsy.

LaCasse said adult finback whales weigh on average between 70,000 and 90,000 pounds. The species can grown to an average length of between 45 and 70 feet, according to the Whale Center of New England.

“It’s not rare to see a whale in the Boston Harbor, but it’s rare to see a dead whale in the Boston Harbor,” said Brian Fleming, command duty officer at the US Coast Guard Base Boston. “The majority of these cases happen out to sea.”

Massachusetts State Police marine officials spotted the whale around 3 a.m. near the Black Falcon Cruise Terminal, and the Coast Guard transported New England Aquarium rescue team members to examine the whale.

LaCasse said the whale floated to within “a couple hundred yards” of the shore of Long Island in Boston Harbor at about 3:30 p.m. Sunday, but the tide carried it back into the harbor.

Authorities will wait for the carcass to wash up so they can examine it and then dispose of it.

Fleming said that about three or four live whales are sighted in Boston Harbor per year.