Fish
Greenland Shark
Somniosus microcephalus · also called gurry shark, grey shark, sleeper shark
The Greenland shark is a large, slow, cold-water shark that turned out to be the oldest living vertebrate on the planet. One female alive today may have been born four centuries ago, before the founding of many modern nations.
Overview
Greenland sharks live in the cold, deep waters of the North Atlantic and Arctic Ocean, around Greenland, Iceland, Norway, Canada, and Svalbard. In the far north they come near the surface in the cold season and descend to 1,000–2,000 m or more in warmer months, following a preferred water temperature of around 1–5 °C. They have also been recorded far to the south in the deep, cold water off the eastern United States and even the Caribbean.
The oldest vertebrate
Sharks lack the bony structures used to age most fish, but the lens of the eye grows in layers throughout life and its central core is formed before birth. Radiocarbon dating of that core in a 2016 study gave the largest sharks ages of 272 to 512 years, with a best estimate near 390 for a 5-metre female. This makes the Greenland shark the longest-lived vertebrate known, and it means the largest individuals were alive during the little ice age.
Life in slow motion
- Growth: roughly 1 cm per year. A 4-metre shark is centuries old.
- Maturity: females do not breed until about 150 years old.
- Speed: it cruises at around 1 km/h and its fastest recorded bursts are slower than a swimming seal — hence “sleeper shark.”
- Metabolism: among the lowest of any shark, matched to near-freezing water.
Diet
Greenland sharks eat fish, squid, and marine mammals, but a large share of what is found in their stomachs is scavenged carrion — including, famously, the remains of reindeer, polar bears, moose, and even a whole horse. Whether they actively hunt seals or mainly find them dead is still unresolved.
Toxic flesh
The shark’s tissues are saturated with urea and TMAO, protective compounds for deep, cold life. Fresh meat is poisonous to eat, causing a syndrome resembling extreme intoxication. Iceland’s traditional hákarl is made by fermenting and drying the meat for months to break these chemicals down.
Threats and conservation
The Greenland shark is listed as Vulnerable. It was once hunted heavily for liver oil (a fishery that took tens of thousands of sharks a year until the mid-20th century), and today the main threat is bycatch in trawl, longline, and gillnet fisheries for halibut, shrimp, and cod. Because it grows so slowly and breeds so late, even modest incidental mortality can drive a decline that would take centuries to reverse.
Greenland Shark: common questions
How old can a Greenland shark get?
Older than any other vertebrate. In 2016, scientists radiocarbon-dated the eye lenses of 28 Greenland sharks caught as bycatch. The largest, a 5-metre female, returned an age estimate of 392 years, with a range of 272 to 512, meaning she was likely born in the 1600s and possibly before Shakespeare died. Even the low end of that range makes the species the longest-lived backboned animal known, ahead of the bowhead whale.
Why does a Greenland shark grow so slowly and live so long?
Extreme cold and a very low metabolism. It lives in water near freezing, its body chemistry runs at a crawl, it swims at barely 1 km/h, and it grows only about a centimetre a year. Slow living generally means slow ageing — less cellular damage from metabolism — and the deep Arctic is a stable, low-predation environment. The trade-off is that females do not reach breeding age until around 150 years old.
Can you eat a Greenland shark?
Not fresh. Its flesh is loaded with urea and trimethylamine N-oxide (TMAO), chemicals that keep its cells working under deep-sea pressure and cold. Eating fresh Greenland shark meat causes symptoms like severe drunkenness — stumbling, vomiting, and worse — and can be dangerous. In Iceland the meat is made edible by burying and fermenting it for weeks and then drying it for months, producing the pungent traditional dish hákarl.
How does a nearly blind, slow shark catch seals?
It is debated. Most Greenland sharks carry a parasitic copepod attached to each cornea, which damages their vision, and they are far too slow to chase a seal. Seal remains found in their stomachs may be scavenged, or the sharks may ambush sleeping seals at the surface or in the water at night, when the seals are less alert. The shark's sense of smell is acute, and much of its diet is clearly carrion, which it detects and follows over long distances.