Gray whales, once rare in San Francisco Bay, dying there at alarming rates

“It’s not unique to their migratory corridor that a lot of whales are dying,” Slaathaug said. “What is unique about San Francisco Bay and this study was that there was such a clear emerging cause of death.”

Some local efforts are under way to reduce vessel collisions.

The Marine Mammal Center, which is affiliated with the study, has developed a program called Whale Smart, to educate vessel operators in the San Francisco Bay on how to interpret whale behavior to avoid close encounters.

In Alaska, where vessels also pose a threat to the whale population, one fleet company partnered with WhaleSpotter, a company that uses AI and thermal imaging to detect the presence of whales, so they can change course well in advance.

Last year, the Center for Biological Diversity, a conservation group, sued the US Coast Guard, which regulates vessel traffic off the California coast, for failing to analyze how vessel routes may harm whales and sea turtles.

“This most recent study about the gray whales reaffirms that we have way underestimated the problem and we are not managing human activities well enough to avoid the whales,” said Catherine Kilduff, senior attorney at the center.

Federal action is needed to reduce the fatal collisions, Kilduff said.

Per the Endangered Species Act, she said, the US Coast Guard should be consulting with the National Marine Fisheries Service,the government agency tasked with protecting the nation’s ocean life and their habitats, when setting shipping lanes to assess impact to marine wildlife, according to Kilduff.

The Coast Guard did not immediately respond to a request for comment on the study’s findings.

Kilduff also suggested mandatory speed limits for vessels. “There are voluntary speed reductions on the west coast, but there is evidence that those aren’t effective. The compliance rate isn’t high enough,” she said.

A 2022 study co-authored by the National Oceanic and Atmospheric Administration found that the average speeds of large vessels had decreased between 2010 and 2019 in voluntary speed reduction zones. But, researchers determined that the cooperation rate of roughly 50% was lower than the amount needed to reduce vessel-strike related mortality to a level that maintains a sustainable whale populations.

“These whales are using the oceans in such a sophisticated way. We can learn so much from them, and if we can figure out ways to avoid killing them, I know that they’ll come back to healthy population levels,” Kilduff said.