CHICAGO (AP/CBS) — Chicago’s Shedd Aquarium has euthanized an Australian lungfish that had been on display there for more than 80 years.

Aquarium officials say the 4-foot-long and 25-pound fish named Granddad was euthanized on Sunday due to “a rapid decline in quality of life associated with old age.” Shedd officials said Granddad was the oldest fish at a U.S. aquarium.

Shedd Aquarium acquired the lungfish in 1933 from the Sydney Aquarium in Australia.

Aquarium officials estimate he was more than 90 years old. Lungfish can live up to 100 years and are a protected species in Australia.

Granddad’s mate died in 1980.

“Granddad outlived several generations of caregivers, and some current staff members never imagined that they’d see him gone during their careers. He seemed as permanent a fixture at Shedd as the terra cotta fishes that decorate the building inside and out,” the Shedd said in an online obituary Monday.

(Copyright 2017 CBS Radio Inc. and its relevant subsidiaries. CBS Radio and EYE Logo TM and Copyright 2017 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed. The Associated Press contributed to this report.)