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How scientists determined the age of the world’s oldest aquarium fish in San Francisco

Methuselah, the world’s oldest living aquarium fish, is fed at the Steinhart Aquarium at the California Academy of Sciences. | Source: Gayle Laird

Two iconic, ancient Methuselahs live in California—one is the world’s oldest tree; the other is the world’s oldest living aquarium fish. 

The latter, an Australian lungfish living in a tank at San Francisco’s Steinhart Aquarium at the California Academy of Sciences, is 92, scientists said Monday. 

The dating (plus or minus nine years) comes thanks to a new DNA analysis led by Ben Mayne of the Australian scientific agency Commonwealth Scientific and Industrial Research Organisation (CSIRO) and David T. Roberts of Australian water utility Seqwater. 

Methuselah—who is named after the biblical patriarch who lived to be 969—arrived in San Francisco via a Matson shipping liner in 1938, a year before the start of World War II, and has far outlived the 231 other fish from Fiji and Australia that accompanied her on her journey. 

The beloved aquatic senior resident was previously thought to be 84. 

Methuselah swims in the Steinhart Aquarium at the California Academy of Sciences. | Source: Gayle Laird

The news comes at a good time for the Steinhart Aquarium, which is set to celebrate its 100th anniversary on Sept. 29. Given that Methuselah could be as old as 100 herself, the aquarium and one of its most famous residents could be sharing a birthday cake. 

The nonagenarian has made a name for herself not only for her advanced age but also her captivating personality—allegedly, the fish loves belly rubs

While it had previously been difficult to date long-lived fish without invasive treatments, the new method relies on a fin clip of less than half a centimeter, which is harmless to the fish, Cal Academy said. 

“Methuselah’s age was challenging to calculate as her age is beyond the currently calibrated clock,” Roberts said. “This means her actual age could conceivably be over 100, placing her in the rare club of fish centenarians.” 

While Mayne and Roberts will not publish the full study of their findings until later this year, the methodology they developed for safely dating threatened fish was published in a June 2021 paper in the journal Molecular Ecology Resources. 

“While her age prediction will improve over time, she will always live beyond the calibrated age clock,” Roberts said. “No other lungfish we know is older than Methuselah.”