The World's Oldest Living Aquarium Fish Is a Californian Who Loves Belly Rubs

The world's oldest living aquarium fish is a nonagenarian.

Methuselah is a 90-year-old, 4-foot-long, 40-pound Australian lungfish that resides at the California Academy of Sciences' Steinhart Aquarium in San Francisco.

Methuselah the fish — named after the biblical figure said to have lived 969 years — is the world's oldest living fish residing in an aquarium, inheriting the title from Granddad. Granddad, another Australian lungfish, died at the age of 95 at Chicago's Shedd Aquarium in 2017.

The California Academy of Sciences isn't certain about Methuselah's sex and exact age because getting this information required a blood draw that could harm the aging fish. The academy believes Methuselah is female but will know for sure after sending a small fin sample to researchers in Australia. This less invasive testing method should reveal the fish's sex and exact age.

Methuselah keeps a "calm," unjaded attitude about her impressive status, Allan Jan, a senior biologist at the California Academy of Sciences said.

"She's an underwater puppy, very mellow, gentle, but of course, if she gets spooked, she will have sudden bouts of energy. But for the most part, she's just calm," he added.

An unripe fig is one of the few things that get Methuselah's scales in a bunch.

"She's a little picky and only likes figs when they are fresh and in season. She won't eat them when they're frozen," Jeanette Peach, a spokeswoman for the California Academy of Sciences said.

Along with ripe figs, Methuselah enjoys snacking on blackberries, grapes, lettuce, clams, prawns, and earthworms. She is one of three Australian lungfish living at the California Academy of Sciences.

Australian lungfish are primitive species with both lungs and gills. 

Australian lungfish is a threatened species and can no longer be removed from Australian waters.