Before being brought to Atlanta, Gasper and Nico, his tankmate, had been housed in substandard conditions in a tank located beneath a roller coaster at an amusement park in Mexico City.
The 17-year-old Gasper had been ill before arriving at the aquarium in October 2005. His health deteriorated further over the past few weeks. That led the aquarium's medical team to make "the difficult decision to humanely euthanize the animal," aquarium officials said in a statement.
Gasper's decline was believed to be the result of his weakened immune system due to years of chronic illness, the aquarium said.
Gasper was in poor health with numerous skin lesions when the new owners of the amusement park agreed to move the whales to Atlanta. Aquarium veterinarians later discovered Gasper had the potentially deadly bone disease osteomyelitis, and he was taken off exhibit for treatment in April.
Hundreds of get-well wishes flooded the aquarium, many from schoolchildren who had become enchanted by the ghostly white whale, who spent much of his time swimming near his tank's big window, appearing to smile for visitors.
Georgia Aquarium chairman Bernie Marcus said in the statement that he was saddened by the news, adding that, "We are comforted in knowing that Gasper received the finest care available in the year he was in the Georgia Aquarium."