A gray whale that was first seen in San Francisco Bay on Feb. 9 stayed in the bay a record number of days, before dying and washing up near Point Reyes last week.
Darrin Allen/Marine Mammal CenterThe whale that broke a record for the longest-known time in the San Francisco Bay was identified Thursday as one of two gray whales that washed up dead at Point Reyes National Seashore over the weekend.
Scientists said a 39-foot adult male gray whale that they had been tracking in San Francisco Bay for over 75 days likely died of injuries from two separate ship strikes as well as from starvation. The cause of death for the second whale, a 37-foot male that appeared to be in good condition, is still unknown.
“To respond to two known gray whales on consecutive days, including one that our team has been actively monitoring for months in San Francisco Bay, is challenging and concerning to say the least,” Dr. Pádraig Duignan, director of pathology at the Marine Mammal Center, said in a press release. The Sausalito marine mammal hospital worked with the California Academy of Sciences and the National Park Service to determine the cause of death.
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Gray whales migrate past the San Francisco Bay between mid-February and mid-May after leaving breeding grounds in Baja California and on the way to feeding areas in Alaska. Until recently, it was unusual for them to stop in the bay, but the population has been struggling in what’s called an “unusual mortality event” since at least 2019, and scientists think they may be stopping to look for food during the long migration.
However, food options inside the bay are slim for gray whales, and heavy ship traffic makes them vulnerable to being hit.
Scientists who had been monitoring the larger gray whale since Feb. 9 in the bay, where they last saw it April 24, already knew it was emaciated. In March they noticed a new scar on its back. After it washed up on North Beach in Point Reyes Station, they found fractures that had begun healing in its spine and ribs that they think were related to an earlier injury. In addition, they found signs of hemorrhaging around its skull, “equivalent to a severe whiplash injury in a motor vehicle collision,” according to the press release, which they think was caused by a more recent ship strike.
The whale was first seen floating offshore on May 6, and then washed up on the beach the next day.
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Two other dead gray whales have washed ashore this season, one in Bolinas in March and the other in San Leandro in April. Scientists think they also died of ship strikes.
Last year, federal officials asked large ships to slow down to protect endangered blue, fin and humpback whales (gray whales are not endangered but also benefit). The new voluntary speed limit of 10 knots (about 12 mph) in three National Marine Sanctuaries that hug the Bay Area coast from May 1 to Nov. 15 was put in place to reduce the estimated 80 whale deaths in California waters caused by ship strikes each year. There are also speed limits of 15 knots (17 mph) for large ships in some parts of San Francisco Bay.
This year, at least eight individual gray whales and one humpback have been observed in the bay. The individual animals can be identified by markings on their flukes.
Reach Tara Duggan: tduggan@sfchronicle.com; Twitter: @taraduggan
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