The decomposing carcass of a North Atlantic right whale was discovered off Chappaquiddick on Sunday, marking the second confirmed death in the past nine months for the critically endangered species.

NOAA spokesman Teri Frady said Wednesday that the whale was spotted near Tom Shoal by recreational boaters. She said scientists from the Northeast Fisheries Science Center (NEFSC) in Woods Hole visited the site Tuesday evening to tag the carcass and collect tissue samples to send to a right whale DNA bank at Trent University in Canada. The scientists were transported by the Coast Guard from station Woods Hole, according to Coast Guard petty officer Zachary Hupp.

Ms. Frady said it’s not clear how long the whale had been decomposing. She said the rotting carcass may be too far gone to bring in and will remain in the ocean while the tissue samples are studied. “At this point there’s not a plan to tow it in for a necropsy, it’s too decomposed,” she said, adding that the body showed signs of shark predation, though the cause of death is still uncertain.

Last November a badly decomposed whale carcass that washed up on Chappaquiddick was identified as a right whale.

The right whale population is at dangerously low numbers and scientists fear it may be headed for extinction.

Ms. Frady said estimates show the population has shrunk to about 400 this year.

The migratory whales travel to the North Atlantic every year to feed in waters that are rich with tiny crustaceans called copeapods. They are especially vulnerable to ship strikes and gear entanglements.

“They are the most endangered whales that we have in our waters,” Ms. Frady said.

In April fisheries scientists worked feverishly to rescue an aging breeding female from gear entanglement on Stellwagen Bank.