Bay Area scientists on Tuesday were trying to determine whether a dead dolphin found washed ashore at Ocean Beach on Monday is one of around 500 coastal bottlenose dolphins believed to live within a mile of California’s shore.
The 9-foot-long, 700-pound bottlenose dolphin marks the 12th of such mammals since 1975 to be recovered by the Marine Mammal Center, which is based in the Marin Headlands but responds to calls on more than 600 miles of California coast, said Laura Sherr, a spokeswoman with the center.
Of the other 11 recovered, two in San Luis Obispo County were found alive and successfully relocated, another was treated and released, and the other eight were either found dead or died in treatment, Sherr said.
“It’s pretty unusual,” said Bill Keener, a Bay Area biologist and co-founder of the Golden Gate Cetacean Research, which studies marine mammals in the region.
Keener has been examining coastal bottlenose dolphins since 2010, and has identified 82 in the Bay Area, between Half Moon Bay and Bodega Bay, using pictures of their dorsal fins, which have unique nicks or notches that occur naturally as the dolphins age.
“We’ve been able to track their movements, and can see [when] repeat animals show up,” he said.
The last dead bottlenose dolphin to wash ashore and be collected by the Marine Mammal Center was in 2013, at Fort Funston.
Coastal bottlenose dolphins only started showing up in the Bay Area in the early 1980s following an El Nino event that brought warmer water to the coast. Before that, they lived off the Southern California shore, though some stayed north even when water temperatures returned to normal.
Keener will compare photos of the dorsal fins his research team has collected to that of the dead bottlenose dolphin to determine whether the animal has been documented before.
“If it’s one of 82 in our catalog, we’ll be able to see where it had been earlier in its life, where it might have spent time hanging out,” Keener said. “It would be very interesting to find out more of its life history.”
Rarely are scientists able to match a dead animal to pictures taken during its life.
The necropsy performed by the Marine Mammal Center on Tuesday will also possibly allow scientists to determine how the dolphin died.
The bottlenose dolphin is among a number of marine mammal carcasses to wash ashore Ocean Beach in the past few days, though it is not believed their deaths are linked. Also on Monday, a dead elephant seal was sighted on the beach, and the Marine Mammal Center received reports Saturday of a dead harbor porpoise at the beach.
Michael Milstein, a spokesman with the National Oceanic Atmospheric Administration Fisheries West Coast Region, said that despite the recent incidents in San Francisco and reports that Bay Area ocean water temperatures are above their historical summer average, there is no known trend of marine mammals washing ashore in Northern California.
“There’s no real pattern that we see at this point,” Milstein said.