Nani, the matriarch of the National Aquarium's colony of dolphins, has died, her caregivers said Tuesday.
At about 44 years old, she was the oldest of the aquarium's eight Atlantic bottlenose dolphins and one of the longest-living dolphins in captivity.
Nani was one of three dolphins purchased from a Texas aquarium and brought to Baltimore to launch its marine mammal pavilion in 1990.
A cause of death has not been determined.
Aquarium officials said they will continue with plans to move the dolphin pod to an ocean sanctuary within the next few years. They announced the plans last June, after years of pressure from animal rights advocates who considered the exhibit to be inhumane.
"We all loved Nani dearly," aquarium Chief Philanthropy Officer Scott Douglas Melton said in an e-mail to supporters. "She was very much a member of the National Aquarium family, and we are heartbroken to lose her."
Nani was the only of the aquarium's current dolphin colony who was born in the wild. She came to Baltimore after the closure of an aquarium in Galveston, Texas.
Together with dolphins named Akai and Nali, she wowed crowds at the aquarium's mammal pavilion opening with flips and splashes in December 1990.
She gave birth to several calves while in captivity, two of which, Beau and Spirit, remain at the aquarium.
Aquarium officials said Nani began acting strangely Monday afternoon. Despite receiving immediate emergency care, she died within hours, they said.
They are investigating the cause of her death.
Female bottlenose dolphins can live to be 50 or older, according to NOAA Fisheries. A dolphin at a Florida aquarium was 61 when she died in 2014, while another of the marine mammals died at 51 at a California theme park in 2011.