MIAMI (AP) — Lolita, an orca whale held captive for more than a half-century, died Friday at the Miami Seaquarium as caregivers prepared to move her from the theme park in the near future.

The Seaquarium posted on social media that Lolita — also known as Tokitae, or Toki — started exhibiting serious signs of discomfort over the past two days. Seaquarium and Friends of Toki medical team began treating immediately and aggressively, but the 57-year-old orca died from an apparent renal condition, the social media post said.

“Toki was an inspiration to all who had the fortune to hear her story and especially to the Lummi nation that considered her family,” the Seaquarium post said. “Those who have had the privilege to spend time with her will forever remember her beautiful spirit.”

Animal rights activists have been fighting for years to have Lolita freed from her tank at the Miami Seaquarium. The park’s relatively new owner, The Dolphin Company, and the nonprofit Friends of Toki announced a plan in March to possibly move her to a natural sea pen in the Pacific Northwest, with the financial backing of Indianapolis Colts owner Jim Irsay.

Lolita retired from performing last spring as a condition of the park’s new exhibitor’s license with the U.S. Department of Agriculture. She’s not been publicly displayed since. In recent months, new upgrades had been installed to better filter the pool and regulate her water temperature.

Federal and state regulators would have had to approve any plan to move Lolita, and that could have taken months or years. The 5,000-pound (2,267-kilogram) had been living for years in a tank that measures 80 feet by 35 feet (24 meters by 11 meters) and is 20 feet (6 meters) deep.