In August, a group of scientists announced they may have found the oldest living vertebrate, the slow-going Greenland Shark. Among the researchers involved was one from the Virginia Institute for Marine Science.
Richard Brill studies sharks and rays at the VIMS Eastern Shore facility in Wachapreague. He traveled to the Arctic with some long-time colleagues to collaborate on a project to try to stop Greenland Sharks from getting tangled in long-line fishing gear. During their hours out on the icy waters (remember Greenland is covered in ice not Iceland) they talked about how they might determine the age of the shark, which grows at an astonishingly slow rate of half a centimeter a year. They brought back a vertebra to try to use a common aging method that looks at growth rings.
“And it turns out there's no growth rings apparent in Greenland Shark vertebra, they just don't show up. So, then we hit on the idea of using eye lenses because you are not the same you, you were several years ago, all your cells are continuously turning over.”
But the proteins in your eye lenses are the same proteins you were born with. Eye lenses don't have blood vessels, otherwise you'd see them. They grow outward, much like an onion, with the innermost part being the oldest. Using bomb carbon dating methods and other data, they found the biggest shark is around 390 years old. Brill says, most of these older sharks may have been taken by a fishery for the shark's liver that was established just after World War II.
“There's some idea they may have cropped out the really big animals at that point and it's only been 60 or 70 years and for a 400-year-old animal that grows that slowly, the population simply hasn't recovered yet.”
So much about the Greenland Shark remains a mystery.
“We don't know where they pup. We have some idea what the age of reproduction is, which may be 150 years old. But we never see the pups and we don't know where they're reproducing, if there's a very critical area that needs to be protected and so on.”
Sonya Fordham founder and president of Shark Advocates International says because Greenland Sharks live so long, they are particularly vulnerable to over-fishing.
“There's some people that still might want to fish it. We want to make sure that's done in a sustainable way. I think it's a combination of safeguarding a really remarkable animal as well as the ecosystem that it's part of. And preserving our chances of learning something about the environment or even ourselves from this type of really long-lived animal.”
As climate change opens up the Arctic to more fishing, Greenland Sharks may become even more rare. And the biggest hurdle for scientists is that the sharks outlive them.
“If you think of our working career of 30 years, just seeing the changes in a shark that lives that long in populations that recover that slowly, would exceed three or four career lengths of any given scientist. So, we all just get a little, tiny peak of what's going on.”
Brill says he hopes to return to Greenland with the group in May.