Mystery as six gray whales found dead after unusually high influx into San Francisco Bay

Independent

3 days ago

Six gray whales have died in the San Francisco Bay Area region in the last week, officials have said.
With the additional deaths, the total number of stranded whales this year has reached 15. Of those, 14 are gray whales, according to the California Academy of Sciences and partners at The Marine Mammal Center.
'In 2025, 14 gray whales and one minke whale have died in the greater San Francisco Bay Area region, with the cause of three of the gray whale deaths determined to be suspect or probable vessel strikes,' the academy wrote in a press release Thursday. 'The Academy and partners at the Center have not responded to this many dead gray whales since the height of the Unusual Mortality Event in 2019 (14 individuals) and 2021 (15 individuals).'
However, the cause of the deaths of the other whales who died between May 21 and Wednesday are undetermined. Those animals died in multiple locations, including Berkeley, Point Reyes National Seashore, and Alcatraz.
'Necropsy response efforts and data collection have been challenging for a number of cases due to inaccessible locations that hinder full post-mortem investigations, as well as poor tissue quality from advanced decomposition, and the lack of available locations to tow for further investigation,' the academy noted.
However, there have also been an unusually high number of sightings around the bay, including 33 individual gray whales. That's more than five times the number of whales that were sighted last year.
Of those, approximately one-third have stayed in the Bay Area for at least 20 days, some of which were emaciated.
Researchers are still working to determine what's driving the massive spike in sightings, and it is expected that gray whales will remain in the area for another one or two weeks before continuing their annual northern migration to feeding grounds in the Arctic.
Dozens of gray whales have died along Mexico's Baja California peninsula since the year's start, and only five mother and calf pairs were identified in Laguna San Ignacio, where wintering whales gather.
One of the main causes of death for whales on both coasts are vessel strikes, and the academy and the center pointed out gray whales can be even tougher to spot in the water than humpbacks and other coastal whales.
To reduce the risk, they've altered ferry lanes based on sighting data and increased communication via the U.S. Coast Guard, so boaters can be 'whale aware.'
If people do see a whale in the bay, they can report the sighting using the Whale Alert app, and people who find dead marine mammals are asked to contact the Academy's department of Ornithology and Mammalogy.