'East River Monster' Is No Mutant
An onlooker inspecting the East River Monster.
Credit: Youtube

The body of a massive, bony creature was spotted in New York City's East River and dragged onto a beach on the Manhattan side of the Brooklyn Bridge May 21. Onlookers assumed it was some sort of mutated animal and dubbed it "the East River monster."

Marine biologists, however, knew immediately what they had on their hands. [Watch a video of onlookers inspecting the East River Monster]

When the carcass, estimated to be 6 to 7 feet long, was first found, it was believed to be some sort of marine mammal. Photos of the creature were sent to the Riverhead Foundation for Marine Research and Preservation for identification.

"We could tell it was an Atlantic sturgeon right away," Kim Durham, a rescue program director and biologist for the Riverhead Foundation for Marine Research and Preservation in Riverhead, N.Y., told Life's Little Mysteries. "They have bony plates all over their bodies. There's no mistaking a sturgeon."

As for the fish's frightening size, sturgeon have been known to grow up to 12 feet. Although this one was only half that length, Durham described it as "pretty impressive." [Read: Can a Goldfish Really Grow to 30 Pounds?]

This isn't the first monster fish to wash up in the area. In July 2008 the infamous Montauk Monster — a dead, yet-to-be unidentified creature — washed ashore on a Long Island beach near Montauk, N.Y.

And there may be more East River monsters to come. Atlantic sturgeon used to be more common in the East River, but their population has declined over the years due to overfishing, according to Durham. It's possible that their numbers are starting to recover, Durham said, which might explain why the massive fish mysteriously appeared.

This article was provided by Life’s Little Mysteries, a sister site to LiveScience.com. Follow Remy Melina on Twitter @RemyMelina