The octogenarian fish, which is old enough to have lived through World War II, was found by the Australian Institute of Marine Science at the Rowley Shoals, about 300 kilometers (186 miles) west of Broome, as part of a study into the longevity of tropical fish.
Researchers looked at three species they said were not commonly targeted by commercial or recreational fishing in Western Australia and the Chagos Archipelago in the central Indian Ocean. The species included red bass, midnight snapper and black and white snapper.
The 81-year-old midnight snapper was identified alongside 10 other fish over the age of 60, including a 79-year-old red bass that was also caught in the Rowley Shoals — an area spanning three coral reefs at the edge of Australia’s continental shelf.
Marine scientists determined the age of the fish by dissecting them and studying their ear bones, or otoliths, which contain annual growth bands that can be counted in a similar way as tree rings.
Brett Taylor, a fish biologist who led the study, said the midnight snapper beat the previous record-holder by two decades.
“Until now, the oldest fish that we’ve found in shallow, tropical waters have been around 60 years old,” he said.
Taylor said the research would help scientists understand how fish length and age will be affected by climate change.