An initial identification suggests that a humpback whale documented for 44 years in Southeast Alaska has died, according to the National Park Service.

Glacier Bay National Park and Preserve Superintendent Philip Hooge announced the whale's death Monday. The humpback, nicknamed Festus, was found floating in the waters off Point Carolus a day earlier, he said.

A charter vessel operator called the National Marine Fisheries Service about the floating whale around 10:20 a.m. Monday. Glacier Bay staff located and towed Festus to shore. Veterinarians are set to conduct a necropsy on Tuesday, according to the Park Service.

"More information on the cause of death and the condition of the whale are expected to be available later this week, after the veterinary examination," Hooge said.

A preliminary examination by biologists pegs Festus at about 40 feet long. The whale has so far been identified through photos of its fluke. It was first documented in 1972 in Lynn Canal and was last sighted in June 2015 in Glacier Bay, according to the Park Service.

"Festus was the longest-sighted humpback whale recorded in Southeast Alaska," the Park Service said.

According to the "Guide to Marine Mammals of Alaska" by biologist Kate Wynne, humpbacks have a lifespan up to 50 years.