Four gray whales found dead in California Bay area in eight days

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Scientists from the Marine Mammal Center and the California Academy of Sciences investigated the death of a gray whale Thursday at Muir Beach.  The team confirmed that the adult female gray whale died of blunt trauma following a collision with a ship.


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This spring, however, they did the dishes.

The carcasses of four gray whales were found in the San Francisco Bay Area in eight days – an alarming series of deaths that is an unusual mortality event, defined by the National Oceanic and Atmospheric Administration (NOAA) as significant mortality of a marine species.

Marine researchers do not know the reason for the wave of whale deaths, the most recent of which was Thursday. But they are determined to find answers, even if the pandemic is having an impact on how efficiently they can conduct their research, said Dr Jeff Boehm, veterinarian and CEO of the nonprofit Marine Mammal Center, the largest world veterinary facility for marine mammals. .

“Four gray whales that died in eight days are just alarming for us,” he said of the veterinary team and staff researchers, who performed autopsies on the whales to determine their cause of death.

Although not endangered, the gray whale population is declining rapidly: 1 in 4 gray whales have died since the last population assessment in 2016, according to NOAA. The agency, along with the Marine Mammal Center and the California Academy of Sciences, is working to find the cause of this decline before gray whales are no longer a biannual visitor to California.

Whales die from ship collisions, malnutrition and entanglement

The whale, a 41-foot female, found near Muir Beach on Thursday, died of a collision with a ship, Boehm said, adding that her injuries included bruising and internal bleeding. It is suspected that another whale that died last week also died following a collision with a boat, but the causes of death of the other two whales are unknown.

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

Malnutrition is likely linked to climate change, Boehm said. Whales move north towards the Arctic in the spring, where the waters are generally rich in invertebrates that bottom whales favor. But if the water temperature rises, the food they feed on may no longer settle in arctic waters, leaving the whales hungry for the next few months, despite not feeding often during their migration.

For the record, Boehm said he saw a “resurgence” in shipping recently after the pandemic slowed international trade. More data is needed to determine how or whether vessels are factored into the unusual mortality event, he said.

A similar death occurred in 2019

A similar death occurred in 2019, when Boehm said three gray whales were found dead within a week. Nearly half of that year, 69 whales were found dead in the United States and 147 whales died overall.

This unusual mortality event was linked to malnutrition, likely due to under-consumption during their summer Arctic feeding season, according to NOAA.

It is not known if 2021 will see similar mortality or if the most recent string of deaths is linked to the unusual mortality event of 2019, Boehm said. The pandemic has delayed robust research projects typical of the Marine Mammal Center, Boehm said, as teams must adhere to Covid-19 security measures while working. But recent events are eerily similar to the events of 2019, he said.

“Four in eight days is just a little more extreme for me,” he said.

The gray whale is not endangered, but its population has declined quite significantly in recent years. The gray whale is not endangered, but its population has declined quite significantly in recent years.

Teams continue to study gray whales in the field and take note of how whales coexist with ships that share Bay Area waters. They monitor things like ship traffic and the speed at which ships travel, but also the condition the whales are in at the start, in case ships alone are not the answer to the recent disappearance.

San Francisco loves 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 of its economic might and major 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 event and, more importantly, create long-term solutions.

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