Three more gray whales have washed up dead in San Francisco Bay, adding to the fatal strandings of five others in the area last month, including a 46-foot fin whale, scientists from the Marine Mammal Center and the California Academy of Sciences said Thursday.

In 2019, the US National Oceanic and Atmospheric Administration announced that it would investigate an unusually high number of gray whales found dead on the North American west coast. The investigation continues.

While the number of dead whales seems alarming, they are actually lower than they have been in the past two years, said Michael Milstein, a NOAA spokesman.

In 2019, 214 washed up on the beaches and coasts of Mexico, the United States, and Canada – 34 in California, 13 in San Francisco Bay. The following year the numbers stayed high: 174.

Scientists believe the numbers observed on land are a fraction of the actual deaths. They say that many more die at sea and are never observed, instead swimming offshore or sinking to the bottom.

Although gray whales are still migrating north from Baja California, fewer whales have stranded this year than in the previous two years – only 68 so far.

While the deaths of these whales are tragic, Milstein offers an opportunity to “better understand what concerns the other 20,000 remaining gray whales out there”.

Most California gray whales migrate from summer foraging areas in the Bering and Chukchi Seas near Alaska to winter calving areas along Mexico’s Baja Peninsula. It’s a 12,000 mile round trip – the longest migration of any mammal.

The whales that appear in San Francisco Bay are migrating north. Most likely, they have not eaten anything since the fall when they left their feeding grounds near the Arctic.

In 2017, NOAA scientists estimated that around 27,000 gray whales had roamed the Eastern Pacific – a population explosion and success in conservation since the 1960s when they were considered critically endangered.

The last three whales to expire were washed ashore between April 27 and May 4 at Oakland Harbor, Angel Island and Lime Point in the Golden Gate National Recreation Area. The one at Lime Point was observed by researchers from the Marine Mammal Center while they were still alive.

Muir Beach saw many visitors and a gray whale carcass on April 17, 2021.

(Carolyn Cole / Los Angeles Times)

Kathi George, director of field operations and response at the center, said the male whale spent 47 days exploring the bay before dying.

“We have seen more whales come into the bay and look around in recent years,” she said, which was both a “cause for celebration and concern”.

She said it was amazing to see these animals so close, but with the dying in the past two years, there is always fear if they behave differently.

The causes of the recent deaths are unclear. Because they washed ashore in inaccessible areas, researchers are unable to perform necropsies on the whales.

Prior to the recent discoveries, George said, three of the five whales that died in the past five weeks were killed by ship attacks. The reasons the other two died are unknown.

An earlier investigation was initiated by NOAA in 1999 and 2000 on gray whales. At that point, more than 600 whales died in two years. A cause was never found; However, scientists wondered if extensive sea ice was affecting the whales’ ability to find food.

Right now, boaters on San Francisco Bay should be slow and careful, George said.

“Be grateful that you have the opportunity to see her so close,” she said. “But be careful.”