The numbers recorded by the International Fund for Animal Welfare (IFAW) represent the largest stranding of a single species in the northeastern United States since the fund began keeping records in 1999.      

Since the strandings began on Jan. 12, rescuers have released 37 of the marine mammals into deeper waters and 92 have died or washed ashore already dead, the fund said.     

Researchers have performed nine full necropsies but have not found any pattern of disease or injury, IFAW spokeswoman Kerry Branon said.     

The dolphins have swum ashore in five towns along the hook-shaped Cape Cod, concentrated in the town of Wellfleet.     

“Wellfleet is like a hook within a hook,” Branon said.      

The dolphins, which tend to get stuck on the bay side of the cape, are assessed by rescuers on site and released in deeper water on the ocean side if deemed healthy.     

Researchers are still trying to determine what brings the dolphins to Cape Cod Bay each year from January to April and why so many have been stranded this year.     

In part it is because dolphins operate with a group mentality, where many may follow one animal toward shallow water, IFAW said.     

Marine biologists who rescue the animals check for signs of stress and body condition, run blood analyses, hearing tests and tag the dolphins with an identifier before releasing them.     

The animal welfare group has also been working to prevent the dolphins from nearing the shore if possible.     

When IFAW gets an early report of a large number of dolphins in the bay, teams in small boats attempt to guide the animals toward deeper water, Branon said.     

“These are off-shore animals that are not used to the tidal fluctuations you experience close to shore,” Branon said.     

IFAW has six dedicated staff who respond to marine mammals and more than 300 rotating volunteers who monitor for stranded dolphins.