According to new studies, scientists have found sharks live longer than first thought.
Scientists realized that previous methods of measuring the ages of shark species were faulty. Scientists would cut through the spines of the sharks and count the pairs of bands to measure age, Nature reported. They would measure age as if looking at the rings inside a tree. Scientists have been using a similar method to analyze the age of rays and other kinds of fish, too.
But sharks aren’t trees, and when they reach maturity some of them stop growing, and the bands in their spines remain exactly the same. This has lead scientists to wrongfully classify sharks as younger than they actually are. Alastair Harry of James Cook University in Australia reviewed the methods in a study. The results are compelling in that they determine decisions of fisheries on what sharks can be safely fished, and may have been miscalculating lifespan.
A 2014 study showed that sand tiger sharks can live twice as long as scientists thought. New Zealand porbeagle sharks were found to be able to live an average of 22 years longer than scientists thought, according to a 2007 study. Harry looked at other methods to determine sharks’ ages that were at odds with the more popular ones. One method is to dye a shark’s spine with chemical markings and then release it into the wild. Another method is to measure the carbon absorbed by animals from nuclear weapons tests that took place in the 1950s.
Newer methods like looking at aspartic acid racemization could come into play. Another method consist of using near-infrared spectroscopy. In any case, the reliance on method’s using the animals’ backbone is minimized.
Scientists were given a shock last year when radiocarbon dating determined that the Greenland shark can live 400 years, Popular Mechanics reported. They used the lenses of dead shark’s eyes to make the determination. The Greenland shark was subsequently crowned the longest living vertebrate. It lives in cold waters and has both a slow rate of growth and a slow metabolism. According to New Scientist, the bowhead whale was previously thought to be the longest living vertebrate, with its 200-year lifespan and ice-cracking head.