Marine mammal specialists descended on the Mendocino Coast over the weekend to evaluate and collect specimens at a rare stranding of a 26-foot-long killer whale found dead Saturday on a beach north of Fort Bragg.

The male orca is the third cetacean to become stranded along the Northern California coast in less than a week. The others were a common dolphin, found dying early last week on a beach in San Gregorio and a sperm whale that washed ashore in Pacifica. The cause of the sperm whale’s death cannot be determined and the reason behind the death of the dolphin is pending a necropsy, but neither bore signs of trauma, such as from being struck by a boat.

It’s also not yet known what killed the orca, but it’s apparently unrelated to the epidemic of dead and dying sea lions being found along the California Coast.

The sea lions are starving while the killer whale, found on a beach at MacKerricher State Park, was in good shape and had a stomach full of harbor seals, said Dr. Shawn Johnson, head of veterinary science at the Marine Mammal Center in Sausalito.

“He had recently had a big meal,” Johnson said.

There were up to six harbor seals in various stages of digestion in its stomach, he said.

A rope with crab pot buoys that was attached to the whale’s tail initially was suspected in the death but was ruled out, at least as a primary cause of death, because it apparently had not prevented the whale from swimming and feeding.

But the rope indicated the animal had at some point become entangled in fishing equipment, something that always is of concern, Johnson said. “It’s sad to find these long-living marine mammals being negatively impacted by people,” he said.

It’s the first time he can recall the Marine Mammal Center responding to an orca entangled in crab pot ropes. It’s also just the sixth time in 40 years that the center has responded to a call about a stranded orca, Johnson said.

But the incidence of marine mammals becoming entangled in fishing equipment is far too common.

An estimated 300,000 cetaceans are killed worldwide each year by fishing nets, according to Whale and Dolphin Conservation, an international group that advocates on behalf of the animals.

The quest for the cause of the orca’s death is continuing microscopically.

Organs and other tissue were collected by people working with the Marine Mammal Center, the California Academy of Sciences, Humboldt State University’s Marine Mammal Stranding Network and the Noyo Center for Marine Science. They are being sent to several locations for evaluation, Johnson said.

The whale carcass also has been removed from the beach. The Noyo Center plans to strip the flesh from the bones — potentially with the assistance of compost and maggots — and eventually display the skeleton alongside a 73-foot blue whale retrieved from a cove south of Fort Bragg in 2009, said Executive Director Sheila Semans.

Currently, the blue whale’s bones are being stored in a warehouse while fundraising to create the center continues.

You can reach Staff Writer Glenda Anderson at 462-6473 or glenda.anderson@pressdemocrat.com. On Twitter @MendoReporter.

School reopenings

Schools back in session next week
Santa Rosa City Schools reopening Oct. 27:
—Biella Elementary
—Brook Hill Elementary
—Burbank Elementary
—Hidden Valley Elementary
—Lehman Elementary
—Lincoln Elementary
—Maria Carrillo High School
—Monroe Elementary
—Piner High School
—Proctor Terrace Elementary
—Rincon Valley Middle School
—Santa Rosa Accelerated Charter School
—Steele Lane Elementary

Districts reopening schools Monday:
— Bellevue
— Bennett Valley
— Oak Grove
— Roseland (It’s temporarily moving its Roseland Collegiate Prep students to two of its elementary schools)
— Sonoma Valley (except Dunbar, which opens Oct. 24)

Districts reopening schools Tuesday
— Kenwood (tentative)
— Rincon Valley

Districts reopening schools Wednesday
— Geyserville (tentative)
SOURCES: Santa Rosa City Schools, Sonoma County Office of Education