Photo: NOAA Okeanos Explorer Program
In 2014, we posted about Joel Abrahamsson, from Gothenburg, Sweden, who set a record for kayak fishing by catching a 15′ long 1,247 pound Greenland shark while fishing from a kayak near the island of Andoria, in Norway. We noted that the fish, which was released, was believed to be over 200 years old. It turns out that the shark could have been much older. Scientists now believe that the Greenland shark is the longest living vertebrate in the world with a lifespan of up to 400 years.
How does one determine the age of a Greenland shark? They are slow swimming sharks who tend to spend their lives in deep, cold waters of the North Atlantic and Arctic Ocean. The age of other shark species is estimated by counting the layers of hard cartilage which build up like rings on a tree. That doesn’t work with Greenland sharks which have very soft cartilage. Instead, scientists recently estimated the ages of 28 sharks by looking them in the eyes. Specifically, scientists used radiocarbon dating of the shark’s eyes to estimate their age. As described in a paper in the journal Science, Julius Nielsen and a team of researchers from the University of Copenhagen, discovered that these apex predators have much longer lives than previously thought. They concluded:
“The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.”
As reported by CNN: “The biology and life history of the deepwater shark species is mostly unknown,” said Cindy A. Tribuzio, a research biologist at the National Marine Fisheries Service. She explained that these “sleeper sharks” are notoriously hard to study and said attempts to determine their age have shown little promise. “This study on Greenland sharks appears to open a new avenue of study into aging these deepwater shark species.”
Though the age estimates cannot be proved — only the sharks know for sure — Nielsen said other evidence, including high levels of accumulated contaminants, supports the results. “Our results demonstrate that the Greenland shark is among the longest-lived vertebrate species,” concluded Nielsen.