Update May 14: The 10th dead whale to be stranded on Bay Area shores turned up on a beach near Pacifica, the San Francisco Chronicle reports.

Original post

A dead gray whale that washed ashore at San Francisco's Ocean Beach on Monday had been struck by a ship and killed by the resulting blunt force trauma, Sausalito's Marine Mammal Center said Wednesday.

The 41-foot whale's injuries included multiple fractures to its skull and upper vertebrae, as well as significant bruising and hemorrhaging.

Scientists from the Marine Mammal Center and California Academy of Sciences performed a necropsy on the whale Tuesday morning.

This is the ninth gray whale to die in Bay Area waters this year, the center said, an unusually high number. It's also the fourth to die after being hit by a ship.

"As gray whale migration season enters its final stages of the season, adult female gray whales and their calves with low body reserves are the last to migrate northward to their feeding grounds in the Arctic,” said Dr. Pádraig Duignan, the Marine Mammal Center's chief research pathologist, in a press release. “These mother whales are worn out and running on empty, making them even more susceptible to negative human interactions, including ship strikes and entanglements.”

But scientists are still trying to figure out why record numbers of the whales are traveling through Bay Area waters, he says. "Are they coming in because they're starving and looking for food in a shallow bay system?"

Whale strikes aren't all that unusual, but they're on the rise, Duignan says.

Some shipping line are taking actions to minimize whale run-ins, says Mike Zampa, a spokesman for the Port of Oakland. He said the number of ships docking at the port has actually gone down in the last four years, by about 20%.