With a spate of recent incidents involving conflict between humans and marine creatures — specifically sharks — it would perhaps bring no comfort to people affected by or generally scared of the toothy animals to know that scientists have been estimating the longevity of sharks mostly wrong till now. Sharks, and even rays, live much longer than previously thought, some even twice as long, new research has shown.
Most current methods for determining the age of sharks rely on counting the growth rings on their vertebrae — similar to what is done with trees and their trunks. In recent research published in the journal Fish and Fisheries, Alastair Harry from the James Cook University in Australia found this method led to often underestimating the age of a given individual, and he found the discrepancy to be quite prevalent across numerous species.
“Age underestimation appears to happen because the growth rings cease to form or become unreliable beyond a certain size or age. Across the cases I studied age was underestimated by an average of 18 years, and up to 34 years in one instance. From the amount of evidence we now have it looks like the problem is systemic rather than just a few isolated cases,” Harry said in a statement Friday.
For his research, Harry decided to look at 53 populations of sharks and rays that have already been thoroughly studied by scientists, because doing so would give him data to compare notes with.
“Age was likely to have been underestimated in nine of 29 genera and 30 percent of the 53 populations studied,” he wrote in the paper, which was titled “Evidence for systematic age underestimation in shark and ray ageing studies.”
The grey nurse shark (Carcharias taurus) can live up to the age of 40 years, which is twice as long as it was hitherto thought to live till. Similarly, the New…