Greenland sharks survive for centuries in icy waters

Greenland sharks cruise the North Atlantic at a pace slower than most people walk, yet some were already adults when the United States was founded.

Their astonishing lifespan has turned this elusive fish into a living time capsule, capturing the imagination of biologists and longevity researchers alike.

Julius Nielsen of the University of Copenhagen leads many of the modern expeditions that tag, scan, and sometimes briefly corral these giants in the icy dark.

Why Greenland sharks live so long

Eye‑lens radiocarbon dating shows females can live at least 272 years, with one specimen estimated at 392 ± 120 years. The method pinpoints birth dates because the lens proteins stop exchanging carbon after a shark pup forms in utero.

“This is the longest living vertebrate that we know of,” said Nielsen, who helped age the record fish. He and colleagues calculate that females do not reach sexual maturity until roughly 150 years, a timetable unheard of in other sharks.

Slow annual growth, barely half an inch, means injuries heal gradually but bones and organs escape the cumulative cellular wear seen in faster‑growing animals.

Researchers suspect a combination of frigid water, low oxygen demand, and genes that police DNA damage all contribute, yet no single “silver bullet” for longevity has appeared.

Greenland sharks have slow heartbeats

Greenland sharks have resting heart rates of about 10 beats per minute and unusually low blood pressure. That’s much lower than what you’d find in other large sharks, and it may help protect their blood vessels from long-term damage like heart attacks or strokes.

Even with such a slow heartbeat, each pump moves a lot of blood, keeping their bodies fueled during slow swimming under Arctic ice.

Doctors are paying attention, hoping this natural “strong pump, gentle pressure” system could offer ideas for treating high blood pressure in people.

Slow bodies save energy

These sharks burn energy very slowly. In fact, their oxygen use is among the lowest ever recorded for a fish their size. That kind of slow metabolism may reduce cell damage over time and help them survive long gaps between meals.

A 280-pound shark might get through the day on fewer calories than a cheeseburger, making a single big meal last for months.

Because the deep Arctic is so cold, they digest food slowly too. Instead of burning energy for speed or growth, they stretch it out for survival.

Why they are toxic top predators

Greenland shark meat is laced with trimethylamine N‑oxide, a compound that stabilizes proteins under high pressure yet renders the raw flesh neurotoxic to mammals.

Icelanders neutralize it through months of fermentation to create the ceremonial dish kæstur hákarl, but few tourists finish more than a nibble.

The species ranks as an apex predator; evidence shows adults seizing fish, squid, and the occasional sleeping seal.

Sightings in the Gulf of Mexico and off Spain reveal a wider range than once believed, hinting at deep‑water corridors that connect polar and temperate seas.

Greenland sharks are at risk

Commercial trawlers unintentionally haul up about 3,500 Greenland sharks each year as bycatch. Because breeding may not begin for a century and a half, losing even sub‑adults chips away at population recovery.

The International Union for Conservation of Nature lists the species as “Vulnerable,” citing low fecundity and expanding deep‑sea fisheries.

Simple changes, switching to LED‑lit nets that deter sharks, banning deep set gill nets in nursery zones, and funding release‑training for crews, can cut mortality without shrinking catches of cod or halibut.

Scientists also urge Arctic nations to establish no‑take refuges around known mating aggregations once those secret sites are found. Protecting a fish that may still be swimming in 2425 demands policies that look far beyond typical political horizons.

The search for hidden nursery grounds

No one has ever observed Greenland sharks mating or giving birth in the wild. Only one pregnant female has been studied, and her embryos suggest the species may be aplacental viviparous, meaning the young develop inside eggs that hatch within the mother’s body.

Females seem to carry up to 10 pups at a time, but the gestation period could last several years. Without regular breeding or nursery sightings, it’s hard to estimate how often they reproduce or whether their range shifts during these vulnerable periods.

This gap in knowledge makes population modeling difficult. Without better data, scientists can’t say how quickly these sharks could recover if current bycatch trends continue.

Tagging mature females may help reveal mating routes or hidden nursery grounds. Learning how and where they reproduce could play a key role in designing effective marine protected areas.

The study is published in the journal Science.

Image Credit: Julius Nielsen

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–