Nearby residents reported seeing the dolphin before midnight with a female dolphin as the tide fell.

Aquarium officials herded the dolphin for several hours Sunday out of the shallow water, into a deeper channel east of Logan Airport, and into the harbor, according to Tony LaCasse, a spokesman for the aquarium. With a sea kayak, a row boat, and a motorboat from the Winthrop harbormaster, officials formed a line to move the dolphin a number of miles.

A stranded adult white-sided dolphin was successfully pushed into the Boston Harbor Sunday after spending the night in shallow water off Winthrop’s Coughlin Park near another dolphin that apparently died overnight, according to the New England Aquarium.


“Apparently, one of the dolphins was able to get back into the water. By daylight, one of the dolphins had died,” LaCasse said in a statement.

On Sunday, officials also used engine noise and slapped water and boats to keep the disoriented dolphin from returning to shallow water.

Aquarium officials plan to perform a necropsy on the dolphin that died. It was described as an “older, adult female with well worn teeth measuring more than seven feet long. She was a little thin and had some skin lesions that will be examined and sampled by Aquarium biologists.”

LaCasse said herding dolphins is more common on the outer Cape, where hungry dolphins chase spawning fish in tidal creeks and salt marshes.

“It is rarely done in the metro Boston area. Residents in this waterfront Winthrop neighborhood said that there is a fair amount of fish activity in that cove,” he said. “As jets roared overhead while taking off from Logan Airport, the picturesque but clearly urban environment was not where one would expect to find dolphins. However, every winter and early spring, the smaller harbor porpoise are in residence throughout Boston Harbor.”


Although less common, LaCasse said dolphins frequent South Boston beaches and the harbor east of the airport. Common dolphins were spotted two weeks ago in the tidal waters of the Neponset River, below a bridge between Dorchester and Quincy, he said.

Alejandro Serrano can be reached at alejandro.serrano@globe.com.