Eight months after the corpse of a North Atlantic right whale calf was found on the shores of Edgartown, federal investigators have determined its official cause of death.

The National Oceanic and Atmospheric Administration Fisheries (NOAA Fisheries) announced Wednesday that the female calf died due to chronic entanglement, bolstering preliminary findings from February. 

The calf was three years old when it died and washed up on State Beach in late January.

Entanglements in fishing lines and vessel strikes are cited as some of the primary causes of death for the endangered species. A rope was found entangled on the calf’s tail when both organizations responded to the call, but the official cause of death wasn’t announced until this week. 

Right whales are teetering on the brink of extinction. As of fall 2023, NOAA Fisheries estimated that there are approximately 360 North Atlantic right whales.

The right whale on the Vineyard, known by the number 5120, was spotted by a person walking along the beach.

The calf was towed from Edgartown to the Vineyard Haven Harbor before being lifted onto a flatbed truck and driven up-Island for post-mortem and burial in Aquinnah. Wampanoag Tribe of Gay Head (Aquinnah) medicine man Jason Baird conducted a ceremony and all but the skeleton was buried. The skeleton was saved to be preserved and used by the tribe.

After the death, NOAA Fisheries determined that the rope removed from the corpse came from Maine. The agency said that, based on its analysis, the rope was the same that is used in fishing traps in the state. 

Right whale 5120 was entangled before the age of two. In August of 2022, the whale was seen off the coast of New Brunswick, Canada, with a serious injury due to entanglement. The injury occurred at some point between May and August of that year.

The whale was also spotted in January of 2023 in Cape Cod Bay. According to NOAA Fisheries, a response team tried to locate and document the whale, but they were unable to because the whale was feeding alongside other whales. 

NOAA Fisheries reported that the Marine Animal Entanglement Response from the Center for Coastal Studies made several attempts to disentangle the whale with little success.

The necropsy is completed and the NOAA Office of Law Enforcement’s investigation remains ongoing.