BOSTON >> Two odd-looking Chinese soft-shelled marsh turtles raised for food in Asia have been seen south of Boston, and there’s concern they could eventually threaten local ecosystems if they become established in New England.

New England Aquarium experts said Saturday it is possible someone decided to release the animals after buying them for cooking. They urge people not to release non-native animals into the wild, and to report any sightings of the soft-shelled turtle.

People on Wollaston Beach in Quincy saw a turtle digging in the sand this past week, and the aquarium’s marine animal rescue team picked it up for identification. A second sighting was reported later in the week.

"The concern is that if it can establish a population, it actually can survive our winter," said Nigella Hillgarth, the New England Aquarium’s president and CEO, and a zoologist. "It could cause major changes in the ecosystem. None of the animals in that ecosystem are adapted to a predator of that size. It eats large amounts of small fish, mussels, clams and insects."

The turtles live in brackish marshes and ponds in eastern Asia. Hillgarth said they are considered endangered in the wild in China, but more than 300 million are raised annually on farms. The animals have become invasive in the Philippines, and have established themselves in Hawaii, California, and Virginia. They have been seen in New York and Maryland.

Hillgarth says the "extraordinary-looking," greenish-brown turtle has a leathery shell and is between 7 and 15 inches long.

"The thing that’s remarkable," she said, "it has a really long snout, and can extend its neck. It’s almost like a little periscope in the water that allows it to breathe. It has this pointy face, and you immediately know it’s something very different."