Granddad, believed to be the world's oldest aquarium fish, dies in its 90s

Granddad, an Australian lungfish who was believed to be the oldest living fish in captivity, died after 80 years at Chicago's Shedd Aquarium.

The fish is estimated to be more than 90 years old, but was euthanised on Sunday after it started showing signs of organ failure and had stopped eating.

Measuring 1.2 metres (4 feet) long and weighing 11.3 kilograms (25 pounds), the fish had been at the aquarium since 1933, after it was acquired from Sydney Aquarium.

It's estimated that more than 104 million people visited Granddad in the decades gone by, as it was the aquarium's longest-living resident.

"For a fish who spent much of his time imitating a fallen log, he sparked curiosity, excitement and wonder among guests of all ages who would hear his story," Bridget C. Coughlin, Shedd Aquarium's president and chief executive officer, told AP.

It had an easygoing life, according to the aquarium, receiving gentle pats on its back and eating leafy greens. The lungfish is native to waters in Queensland, but is a protected species in its homeland.

The fish can live up to 100 years old, and is known as a species with a low mortality rate. They don't spawn juveniles often either, only doing so on an average of every five years, according to the Queensland Museum.

Suffice it to say, you won't see the likes of Granddad for a long time.

Associated Press contributed reporting.