Otiliths accumulate additional layers of calcium carbonate at regular intervals so that, as with tree-rings, counting them can provide a reliable estimation of age.
The researchers found that an upper age range of 80-90 years was common in bigmouth buffalo, well beyond the previous record age of 73 years for a freshwater drum.
The finding was verified using bomb carbon dating, a method based on the mid-20th-century atomic bomb tests that temporarily doubled carbon 14 content in the atmosphere, leaving detectable traces in the otiliths.
In some of the bigmouth buffalo populations studied, more than 90% of the fish were more than 80 years old. The biologists believe that this is the result of dam-building on rivers in the 1930s restricting the fishes’ access to their natural spawning grounds, preventing them from producing young.
Predated on by anglers (not to mention biologists) and without natural replenishment of their stocks, the elderly bigmouth buffalo populations are now in decline.
The research is published in Communications Biology.