3 more gray whale carcasses spotted in bay this week.
In a disturbing pattern going back to early April, three more dead gray whales have been sighted in the San Francisco Bay in the past week.
The whale carcasses were spotted in Tiburon, the Port of Oakland and Angel Island State Park, but unlike previous whale sightings, none were accessible enough for scientists to determine the cause of death.
Since the beginning of April, four previous gray whale deaths and one fin whale death have been reported in San Francisco Bay, according to the Marine Mammal Center, the Marin County veterinary hospital whose scientists perform necropsies on the large animals. They determined that three of those whales died from ship strike injuries while the cause of death for the other two could not be determined.
“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,” Kathi George, director of field operations and response at the Marine Mammal Center, said in a statement.
As for the most recent deaths, the gray whale spotted floating in Tiburon’s Keil Cove on April 27 had been previously observed by scientists in the bay since midMarch — individual whales can often be identified by marks on their flukes — and had appeared to be underweight. It has since drifted to Kirby Cove in Sausalito.
The Marine Mammal Center is in discussion with the National Oceanic and Atmospheric Administration to have the three dead animals towed out to sea.
The deaths of gray whales this spring are part of what the National Oceanic and Atmospheric Administration has declared a “unusual mortality event” going on since 2019. That year, there were 13 reported whale deaths during the spring migration, while in 2020 there were five. Scientists have found that ship strikes as well as malnutrition are the main causes of deaths in gray whales during the dieoff.
Gray whales have been stopping in San Francisco Bay on their springtime migration route from breeding grounds in Mexico to feeding areas in Alaska for unusually long amounts of time in recent years, which makes them more vulnerable to ship strikes.
It’s also a sign that they are not getting enough to eat in Alaska before they make the journey to Mexico and back, Bill Keener, research associate at the Marine Mammal Center, told The Chronicle. The reason may have to do with shifting availability of feed because of climate change or because the population has rebounded in recent years and is too large to be sustained by the available food at their traditional stopping place in Alaska, Keener said.