The oldest aquarium fish in the world lives in San Francisco. She likes belly rubs

“She’s picky,” Jan says. “And being that old, I allow her to be picky.”

Methuselah is special for reasons other than her age and proclivity for fresh fruit. Lungfish are “living fossils,” which can breathe on land and in water. The lungfish’s evolutionary advantages include the ability to survive in mud until rains return and use limb-like pectoral fins to shuffle from pond-to-pond.

“They are a very, very primitive fish,” says Jan, a Bay Area native who has worked at Steinhart Aquarium for 15 years, caring for Methuselah most of that time. “They’re kind of the link between fish and amphibians. They actually have a lung, so they have to breathe air.”

I’ve known about Methuselah since my own childhood in the 1980s, when the fish was already being celebrated for its longevity. (“Gad, I hope it’s not on the menu at Tadich (Grill),” Chronicle columnist Herb Caen wrote in 1992.)

As I finished recording one of The Chronicle’s first audio tours on the VoiceMap app last month — “Secrets of Golden Gate Park: Graft, Gunfire and a 90-Year-Old Fish” — I contacted the Cal Academy for a post-pandemic health check, confirming that “Methuselah is indeed alive and well.”

Methuselah came to San Francisco on a steamship from Queensland, Australia — a Matson liner — in 1938. She was grown, and believed to be at least 7 years old. The name Methuselah is a Biblical reference; he was Noah’s grandfather, who lived to 969 years old. Methuselah the fish is now about 3 1/2 feet long and 40 pounds, and likely still growing. Jan said even elderly lungfish continue to grow.

Her first appearance in The Chronicle was 1947.

“The most valuable fishes in the Steinhart Aquarium are a pair of Australian Lungfishes,” a 1947 Chronicle column read. “These strange creatures — with green scales looking like fresh artichoke leaves — are known to scientists as a possible ‘missing link’ between terrestrial and aquatic animals.”

While many of the old Steinhart Aquarium’s memorable exhibits are long gone, including Pacific white-sided dolphins and a rescued manatee named Butterball, several of the fish and reptiles have established impressive tenure. Jan said the museum’s alligator gars — large freshwater fish with rows of sharp teeth— are in their 50s and 60s, and snapping turtles are likely in their 70s. The second-oldest Steinhart Aquarium lungfish is at least 60 years old.

When the Shedd Aquarium’s lungfish “Granddad” died in 2017, after 84 years at the Chicago museum, Methuselah became the world’s oldest aquarium fish.

A visit behind the scenes, with a network of large pipes and filters and a catwalk around the enclosure, reveals a nylon “jump guard” at the top of the tank, added a decade ago after Methuselah lept outside, spending up to an hour on the floor before she was discovered. (The escape happened at the aquarium’s temporary 875 Howard St. home.)

Methuselah is also unique for several high-maintenance quirks, which have caused alarm — and comedy — at the aquarium.

“Sometimes she’ll just start floating, tail up,” Jan explains. “And then we’ll get a bunch of calls. ‘What’s wrong with the fish? What’s wrong with the fish!’ … To the public, it looks like she’s in distress.”

The baguette-shaped fish seemed to go tail up more when housed with the Aquarium’s other two lungfish named “Small” and “Medium,” so she was moved to her own shallow tank.

(The Cal Academy doesn’t know Methuselah’s sex for sure — confirmation would involve a risky blood draw — but Jan strongly suspects that the fish is female.)

Jan says he works on “enrichments,” which include training and tactile interactions, where he touches the fish to give them comfort and make them more acclimated for inevitable weighings and medical procedures. Asked what types of tactiles Methuselah enjoys, he says “literally belly rubs.”

The bond between fish and keeper was strong before the pandemic, but after living with no visitors for more than a year, the relationship regressed.

“When we were closed for COVID, all the animals would just chill out and relax and not have noise and people pounding the glass,” Jan said. “And then when we reopened it was kind of a shock. For Methuselah, her training went back to day one.”

But the connection is growing again. During a recent visit to the tank’s edge, Jan signals with a tap on the water, then offers Methuselah some smelt, first checking if the fish goes to her “don’t bother me zone,” which would end the interaction.

After a 30-second pause that feels a little passive-aggressive (“I always let her come to me”), the fish swims a slow lap then takes the food from his hand. But she bristles when Jan tries to rub her chin. A year ago, Jan says, he could place both hands under her belly and inspect her limbs with no protest.

Jan says he tells new volunteers and biologists, “Just treat them like underwater puppies. They’re super, super gentle. And they’re very deliberate in their movement. And very predictable, which is what I like in a fish.”