Three Additional Dead Gray Whales Reported in San Francisco Bay

Scientists have responded to reports of three dead gray whales in San Francisco Bay over the last week. Experts at The Marine Mammal Center, the world’s largest marine mammal hospital, along with their partners at the California Academy of Sciences, are unable to determine the cause of death for the animals due to inaccessible or unsafe locations as well as shifting tides. Discussions are ongoing with NOAA to safely tow the whale carcasses into open ocean where they might naturally decompose.

“Over the last few years, our experts have observed gray whales frequenting San Francisco Bay in greater numbers and for longer periods of time,” says Kathi George, Director of Field Operations and Response at The Marine Mammal Center. 

These whales are at increased risk from human activity, which is why we are committed to better understanding the ongoing challenges and threats these animals face so we can safely share the ocean and bay with them.

Since early April, scientists from the Center and its partners, including California Academy of Sciences, have investigated four gray whales and one fin whale that were all found in the San Francisco Bay Area. Three of those animals died due to injuries consistent with a ship strike. Unfortunately, scientists will not likely be able to determine a cause of death for the most recent three dead whales.

In 2019, from March through May, scientists investigated 13 dead gray whales in the San Francisco Bay Area. In 2020, the Center responded to five dead gray whales in the same time period. Elevated strandings of gray whales in poor body condition since early 2019 across the species’ entire migratory range caused the National Oceanic and Atmospheric Administration (NOAA) to declare an Unusual Mortality Event (UME) for the species that is ongoing. The Center’s team participates as an investigator on NOAA’s gray whale UME working group.

"Nobody wants to see whales die,” says Justin Viezbicke, California Stranding Network Coordinator with the National Marine Fisheries Service. “Our partners, like The Marine Mammal Center, help us learn from the whales that have died to understand the factors affecting the remaining 20,000 gray whales still migrating north off the West Coast.”

Researchers from the Center have observed increased numbers of gray whales in the San Francisco Bay this spring as the population continues their northerly migration to cool, food-rich Arctic waters. It is critical for boaters and people on the water to keep a safe distance from whales and report sightings to the Center’s hotline at 415-289-SEAL(7325). All marine mammals are federally protected, and the public should not approach any whale, alive or dead.

The three whales washed ashore between April 27 and May 4 in Tiburon, the Port of Oakland, and at Angel Island State Park. Each animal was in a location that was inaccessible for scientists to perform a full necropsy, or animal autopsy, to investigate a cause of death. The gray whale found in Keil Cove in Tiburon later drifted to Lime Point in the Golden Gate National Recreation Area. Researchers at the

Center observed this individual whale while it was still alive, and noted that it spent 47 days exploring San Francisco Bay and was underweight.

Malnutrition, entanglement and trauma from ship strikes have been the most common causes of death in whales studied by the Center’s research team in recent years. The Center’s researchers study the locations and behaviors of whales in the San Francisco Bay so that informed decisions can be made to better protect whales. Public funding and support for this investigatory work is essential.

Scientists from The Marine Mammal Center and the California Academy of Sciences were able to collect some limited samples from the three different whales this week for research purposes. Typically, California Academy of Sciences archives various parts of each specimen (baleen, pelvic bones, blubber, muscle, etc.) in their scientific research collection thus making them available to scientists from around the world.

For more information or to set up an interview on this topic, please contact us at media@tmmc.org.

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