Four gray whales were found dead in the Bay Area of ​​California within eight days

The carcasses of four gray whales have been found around the San Francisco Bay Area in eight days – an alarming series of deaths constituting an unusual death event defined by the National Oceanic and Atmospheric Administration (NOAA) as a significant die-off of a marine species.

Marine researchers do not know the reason for the wave of whale deaths, the most recent of which occurred Thursday. But they are determined to find answers, even as the pandemic affects the efficiency with which they can conduct their research, said Dr. Jeff Boehm, a veterinarian and CEO of the nonprofit Marine Mammal Center, the world’s largest veterinary facility for marine mammals. .

While not threatened, the gray whale population is rapidly declining: 1 in 4 gray whales has died since the last population assessment in 2016, according to NOAA. The agency is working with the Marine Mammal Center and the California Academy of Sciences on the find the cause of that decline before the gray whales are no longer a biennial visitor to California.

Whales die from ship strikes, malnutrition and entanglement

The whale, a 41-foot female, was found on nearby Muir Beach on Thursday and died from a ship attack, Boehm said, adding that his injuries were bruises and internal bleeding. Another whale that died last week is believed to have also died from a boat attack, but the causes of death for the other two whales are unknown.

Necropsions conducted in recent years have identified the three most common causes of gray whale death: malnutrition, ship attacks and entanglement, Boehm said.

Malnutrition is likely linked to climate change, Boehm said. The whales travel north to the Arctic in the spring, where the waters are typically rich with invertebrates that prefer the bottom feeding whales. But if water temperatures rise, the food they feed on may no longer find their home in the Arctic waters, leaving the whales starving for months to come, when they don’t eat often as they migrate.

Anecdotally, Boehm said he has recently seen a “resurgence” in shipping after the pandemic slowed international trade. However, more data is needed to determine how and if the ships play a role in the unusual mortality, he said.

A similar die-off took place in 2019

A similar die-off occurred in 2019, when Boehm said three gray whales were found dead within a week. Nearly halfway through that year, 69 whales had been found dead in the US and a total of 147 whales.

It’s not known if 2021 will see a similar die-off, or if the most recent series of deaths is linked to the unusual 2019 deaths, Boehm said. The pandemic has hampered the Marine Mammal Center’s typical robust research projects, Boehm said, as teams must adhere to Covid-19 safety precautions on the job. But recent events are alarmingly similar to what happened in 2019, he said.

“I think four in eight days is just a bit more extreme,” he said.

Teams continue to study gray whales in the field and see how the whales coexist with the ships that share Bay Area waters. They monitor things like ship traffic and the speed at which the ships are sailing, as well as the condition of the whales, in case ships alone are not the answer to the recent die-off.

San Francisco loves the whales that travel twice a year, Boehm said.

“What a remarkable thing to have, an urban center like the San Francisco Bay Area, with all its economic power and this important population center, right next to waters teeming with wildlife,” he said.

When the gray whale population suffers, so do the rest of the Bay Area’s marine ecosystems, Boehm said. It is therefore crucial that marine biologists find answers to the most recent unusual mortality rates and, more importantly, come up with long-term solutions.