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Mercury News: Lots of Gray Whales Are Swimming Under the Golden Gate Bridge into San Francisco Bay. Why?

June 24, 2024
  • Behavior
  • Pathology
  • Population monitoring

Popular species faces risks from collisions with big ships, as researchers look for clues

Published in The Mercury News: June 24. 2024

Gray whales have been veering off their normal routes along the West Coast and swimming under the Golden Gate Bridge into San Francisco Bay in unprecedented numbers.

Using thousands of photographs of distinctive markings on the whales’ backs to identify them, marine scientists have confirmed that at least 71 different gray whales — and possibly 84 or more — swam into the bay between 2018 and 2023, with some staying for more than two months, raising their risk of being hit by cargo ships, oil tankers or other large vessels.

From 2010 to 2017, only about 1 or 2 of the giant marine mammals came into the bay every year. Last year, however, there were at least 16, and in 2019 there were at least 21.

We think it has a lot to do with the fact that the whales haven’t been getting enough food.

“We think it has a lot to do with the fact that the whales haven’t been getting enough food,” said Bill Keener, a biologist with The Marine Mammal Center, a non-profit group in Sausalito. "They may be weak and resting for a while, or they may be looking for an alternative food source."

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population monitoring
Bill Keener
Gray Whale