Experts identified the large carcass seen floating in Boston Harbor on Tuesday morning as that of a large basking shark.
The animal was originally spotted squished against the bow of a container ship heading into the harbor on Friday, May 13. It flopped off of the hull and slipped beneath the surface.
When it re-emerged, the aquarium’s marine animal rescue team traveled over on Boston police boat to study it.
By Tuesday morning its flesh had started to break down, and it bobbed up head first. That made it difficult to identify at first, said Tony LaCasse, a spokesman for the New England Aquarium.
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“We estimate that the carcass was at least 25 feet long. It could have been more,” LaCasse said. “The challenges with this carcass was it was floating vertically in the water. It was just head and shoulders.”
The researchers were not able to determine how the shark died — it was “decimated” by the process of decay, he said. It may already have been dead before it was struck.
Now its fate is up to the tide. It has been released into the Outer Harbor, where it is expected to sink down to the sand become a “feast for crabs and lobsters,” LaCasse said.
When the sea creature was alive, it was harmless to humans, despite being a member of the ocean’s second-largest species of shark. Basking sharks eat plankton, not people.
“This guy and other basking sharks just migrated into New England waters in early-to-mid-April, and they will spend through the Autumn feeding,” LaCasse said.
Nevertheless, they’re likely to spook beachgoers. The creatures’ dorsal fins to a layman look just like that of a fearsome great white.
“Once people see the size, they’ll call in and say, ‘I saw the biggest great white shark in history,’” he said. “But what will happen is we’ll actually see a picture of a shark that’s 25 feet long and we know it’s not a white shark.”
A big white shark, he said, is 15 feet long.