When you might live for up to 500 years, time moves a little different for you. A day might feel like a second, a week might feel like a day, and so on and so forth.

When was the last time you ate?

Have you seen any sharks that look like you?

These might be some of the questions the world's longest-living vertebrate has. Meet the Greenland shark (Somniosus microcephalus), one of the world's longest-living animals. A sleeper shark that can reach lengths of 23 feet (7 meters), these predators are primarily found in the cold-water environments of the North Atlantic and Arctic Oceans. Little is known about them, which is a problem given the growing pressures from climate change and expanding commercial fisheries in the Arctic.

The Greenland shark (Somniosus microcephalus) is a member of the sleeper shark family Somniosidae ... [+] (order Squaliformes) that is the longest-living vertebrate known.

The very same superpower that makes them unique - longevity - makes them especially vulnerable to overfishing. In fact, overfishing (when too many fish are caught and there are not enough to sustain a healthy population) is the biggest threat facing sharks as a whole. Recent studies suggest that three-quarters of oceanic shark and ray species are threatened with extinction, with overfishing as the primary cause. But it is especially worrisome for an animal who doesn’t sexually mature until they are 150 years old.

The Greenland shark fishery has been of great importance in Greenland until 1966, where their livers and skins were exported for the production of oils for lamps, engine oil and vitamin A rich oil, and the skin for leather production. While the shark’s skin is poisonous if consumed raw, it can be fermented or repeatedly boiled in order for safe consumption. Laboriously fermented, dried, and cured, it is a regional delicacy in Iceland and the dried meat is popularly used for sled dogs. Records of trade with shark livers in Greenland during 1850– 1938 estimate annual shark landings of up to 44,000 individuals and up to 800 tons of shark liver.

The historical targeted fishing led to a decline in the population that was only exacerbated by their bycatch numbers. According to the International Union for Conservation of Nature (IUCN), an estimated 3,500 Greenland sharks are accidentally caught as bycatch - the incidental capture of non-target species - every year in the Northwest Atlantic, Arctic Ocean and Barents Sea. Although very difficult to estimate, Greenland shark populations are thought to have declined by 30–49% or even more, leading to the IUCN to change their Red List assessment from “Near Threatened” to “Vulnerable.”

But some researchers did not think this was enough.

The Greenland sharks (Somniosus microcephalus), who are the world's longest-living vertebrate and ... [+] one of the world's longest-living animals.

So at its 44th Annual Meeting in Portugal, when the Northwest Atlantic Fisheries Organization (NAFO) prohibited the retention of Greenland sharks in international waters, scientists and conservationists rejoiced. “It was a long time coming, but not a long time in the life of a Greenland shark,” Sonja Fordham, president of Washington, D.C.-based Shark Advocates International, who attended the recent NAFO meeting in Portugal, told Mongabay. “We were glad that it finally went through, and it’s the first for that kind of protection for NAFO.”

NAFO is a Regional Fisheries Management Organisation that ensures the long-term conservation and sustainable use of the fishery resources in the North-West Atlantic. An intergovernmental organization, they are responsible for the management and conservation of 19 commercial fish stocks (including cod, haddock, hake, and swordfish) based on scientific advice and evidence. With 12 members - 11 nations and the European Union - it isn’t a small organization! And they all agreed on protecting Greenland sharks back in 2018, when their scientific council suggested a ban on retaining the long-living giants. However, only the USA and the EU adopted a partial ban, as well as implemented catch reporting requirements. The advice was finally adopted this year with support by all member countries.

“There’s still so much we don’t know about them: how many they are, their abundance, their population structure, we have no idea where they go to mate, or where they go to have their pups. We don’t know how many pups they have or how often they reproduce,” Brynn Devine, an Arctic fisheries adviser at Oceans North, told Mongabay. “And that makes conservation planning particularly challenging because those are the things that you need to know to understand how at risk a species is to things like bycatch.”

For one thing, it’s a bit challenging to conservation plan for an animal whose range you don’t fully know. A Greenland shark was spotted near a Caribbean reef earlier this year, despite until recently being thought to live only in Arctic waters. It is unclear why this shark was off Belize and if this was normal for the species as a whole; the possibility this individual was a hybrid between the Greenland shark and Pacific sleeper shark (Somniosus pacificus) was floated. World Greenland shark expert University of Windsor Associate Professor of Biology Nigel Hussey gave the team four satellite tags in case another Greenland shark pops up is the Western Caribbean.

More than one-third of all sharks, rays, and chimaeras are now at risk of extinction because of ... [+] overfishing, according to a new study.

Devine also has another point: scientists don’t really know how many of these sharks die once caught up in fishery nets and other tools. Like many other shark species, their survival depends on the kind of gear that is used and how long they were caught up for. Under the new rules, intentional fishing and the keeping of Greenland sharks accidentally caught as bycatch would be prohibited. There may be exceptions if a country has a ban on discarding fish, such as Iceland, Norway, the Faroe Islands, or Greenland. These exceptions are only applicable to sharks caught by accident - not those intentionally caught. According to Fordham, returning Greenland sharks to the water if they are accidentally caught is an important part of implementing the new rule. “Scientists say they’re good at playing dead, so they’re often assumed dead and may not be treated particularly carefully to get them out of the net. And it can also be hard to get them out of the net,” she says.

Oceans North's Vice President of Operations and Projects, Susanna Fuller, who also attended the NAFO meeting, said the decision to protect Greenland sharks was a “huge breakthrough.” However, she said that NAFO still needs to work on aligning fishing quotas with scientific knowledge to safeguard vulnerable ecosystems in the future. The progress being made in the region overall, she said, encourages her. “When one measure is taken,” Fuller told Mongabay, “usually it starts to build momentum for more.”