Rescuers who helped free more than 100 dolphins from the Cape Cod coast said they have confirmed that the mass stranding that began June 28 was the largest involving dolphins in U.S. history.
There have been two previous recorded incidents in Hawaii and the Florida Keys where dolphin species were seen swimming in shallow water, but the Cape Cod incident marks the largest number of dolphins stranded in a single event, according to the International Fund for Animal Welfare, which helped lead the rescue.
A review of data and aerial imagery this week revealed that a total of 146 dolphins were involved in the stranding, according to the international fund’s communications director, Stacey Hedman.
The group estimated that 102 dolphins survived the multi-day event. There were 37 natural deaths and seven dolphins had to be euthanized.
Response efforts continued on a smaller scale, including the rescue, relocation and release of nine of the same Atlantic white-sided dolphins on July 2.
That day, 11 dolphins were found stranded near Powers Landing in Wellfleet, Mass. Two were euthanized and nine were transported to a custom-built mobile dolphin rescue clinic vehicle, where veterinarians and biologists can administer fluids and other treatments while navigating to deeper waters, the director said.
In this case, she explained, the dolphins were released near Herring Cove Beach in Provincetown. Satellite tags tracked several of the animals safely offshore.
There is no specific reason why the dolphins stranded.
PHOTO HANDOUT, AGENCE FRANCE-PRESSE
A lifeguard tries to direct dolphins to avoid their stranding on June 28.
Rescuers faced many challenges as they tried to guide the dolphins back to open water, including difficult muddy conditions and the fact that the dolphins were spread out over a large area.
In some rescue attempts, workers started on foot, herding the creatures into deeper water, and then used small boats equipped with acoustic alarms, which make noise to attract the creatures.
Several dolphins have died at Gut — or Great Island — in Wellfleet, near the Herring River. The Gut is a frequent stranding site, which experts say is due in part to its hooked shape and extreme tidal fluctuations.
“This stranding took a tremendous effort from our staff, volunteers and partners over several days,” Hedman said, adding that with a survival rate of about 70 percent, the group considers the response a success.
The organization has also received reports from whale-watching vessels that have seen some dolphins – identified by temporary tags – now swimming among groups of hundreds of other dolphins that were not part of the stranding.
Among those contributing to the overall rescue effort were more than 25 staff members from the International Fund for Animal Welfare and 100 trained volunteers. The group also received support from Whale and Dolphin Conservation, the Center for Coastal Studies, AmeriCorps of Cape Cod and the New England Aquarium.