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FRIDAY HARBOR, Wash. — The oldest member of the small population of endangered Puget Sound orcas has been missing for months and is now likely dead, bringing the toll of dead or missing whales to seven in 2016, researchers in Washington state reported.

The orca labeled J2 and nicknamed "Granny" had been spotted thousands of times over 40 years of orca surveys but has not been seen since October, according to the Center for Whale Research on San Juan Island, a nonprofit group that keeps the federal government's annual census of the whales.

"With regret we now consider her deceased," researcher Ken Balcomb wrote in a post on the center's website Saturday.

She was typically seen at the head of the J pod, one of three family groups of whales that travel with their mothers or grandmothers, but has not been spotted for weeks. Other members of her family have been photographed and counted.

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An orca whale designated J2, and nicknamed Granny, pokes her head upward while swimming in the Salish Sea near the San Juan Islands, Wash. on July 3, 2016. Mark Malleson / The Center for Whale Research via AP, file

Individual southern resident killer whales that spend time in the inland waters of Washington state are identified by unique black and white markings or variations in their fin shapes. Each whale is given a number and a name.

A 1987 published study estimated that J2 was born in 1911, putting her age at 105. There is a 12-year margin of error so she could be older or younger, Howard Garrett of the Orca Network said in an email.

Despite a birth boom in 2015 that saw eight orca babies born, the intensely tracked population of southern resident killer whales is down to 78 as of Dec. 31, the center said.

Despite a decade of research, protection and recovery efforts, the orcas continue to struggle primarily due to a lack of food, pollution and disturbances by marine vessels. They were listed as endangered in 2005.

There were more than 140 animals decades ago. That number declined to a low of 71 in the 1970s when dozens of the mammals were captured to be displayed at marine parks and aquariums across the country. The numbers have fluctuated in recent years.

Seven were declared missing or dead in 2016, including an 18-year-old male whale found dead off the coast of British Columbia last month.

Canadian officials say the preliminary necropsy found that the 22-foot long whale was likely struck. It is unclear whether it was hit by a boat or another animal.

The agency is investigating the cause and conducting more blood and tissue tests on the animal.