A bottlenose dolphin that spent more than four decades in captivity at Six Flags Discovery Kingdom in Vallejo, California, was euthanized last month, prompting new calls to move the park’s remaining dolphins.
Chelsea was euthanized July 14 because of “multiple recurring chronic diseases” and a declining quality of life, according to a federal Marine Mammal Inventory Report cited by NBC Bay Area.
Chelsea had long been part of the park’s marine mammal program, appearing in dolphin shows and visitor encounters, ABC7 Bay Area reports.
Her death has reignited a long-running campaign by People for the Ethical Treatment of Animals (PETA) to end those programs. On Aug. 17, PETA asked Six Flags to move its surviving dolphins to seaside sanctuaries and terminate its swim-with-dolphin feature.
Chelsea Had Been in Captivity Since 1983
Chelsea is gone, but her story shouldn't be forgotten 💔 pic.twitter.com/gAzftij3zM
— PETA (@peta) August 21, 2026
PETA says Chelsea was captured from the Gulf of Mexico in 1983 and arrived at what is now Six Flags Discovery Kingdom in 1985.
She gave birth to six calves during her years in captivity, according to PETA. A 2008 Associated Press photo published by ABC7 Bay Area shows Chelsea swimming alongside her then-2-month-old calf, Mavrick.
PETA argues that dolphins’ physical and social needs cannot be adequately met in captivity. Six Flags Discovery Kingdom, meanwhile, says it is committed to providing a “safe and healthy home” for the animals in its care and promoting education and conservation.
The park continues to advertise dolphin attractions. Its Dolphin Discovery program offers guests an “In-Water Dolphin experience” for $129.99, although the park currently lists it as unavailable. Six Flags also advertises a dolphin presentation called So Flippin’ Fun.
Now the Fight Is Over the Dolphins Who Remain
In a letter to Six Flags Entertainment CEO John Reilly, PETA called for the remaining dolphins to be transferred to seaside sanctuaries, where they could live in larger, more natural environments while remaining under human care.
PETA President Tracy Reiman said the organization believes Chelsea should have had a life outside the park’s tanks. “It’s too late for her,” she wrote, as reported by NBC Bay Area, “but there’s still time to do the right thing for the surviving dolphins.”
The group also asked Six Flags to immediately end its swim-with-dolphin program. PETA has criticized both the park’s performances and its hands-on encounters with visitors.
As of August 19, NBC Bay Area reported that Six Flags Discovery Kingdom did not respond to the outlet when it requested comment on Chelsea’s death and PETA’s demands.