Greenland sharks are estimated to live for centuries because they grow exceptionally slowly in cold, deep waters and do not reach sexual maturity until roughly 156 years of age. The best-known estimate—392 ± 120 years for a 502-centimetre female—is a radiocarbon-based model with a very wide 95.4% probability range, not a confirmed birthday. Their slow replacement rate makes accidental capture in fisheries a serious conservation concern, while climate-driven habitat changes remain a plausible but unquantified additional pressure.
How scientists estimate the age of a Greenland shark
Most shark-aging methods count growth bands in hard tissues. That approach is difficult for Greenland sharks (Somniosus microcephalus): they lack fin spines, and their vertebrae are too soft to provide reliable, countable bands. Researchers therefore needed a biological material that records time in another way.
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Radiocarbon in the eye lens
The landmark 2016 study measured radiocarbon in the nuclei of eye lenses from 28 female Greenland sharks measuring 81 to 502 centimetres in total length. Lens proteins form before birth and remain in place, so the radiocarbon signal in the lens nucleus can be compared with the known rise and subsequent decline of atmospheric radiocarbon associated with nuclear testing. That comparison gives an estimated birth period rather than a directly observed age.
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The study is described in Nielsen and co-authors’ 2016 paper. Its abstract says: “Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.” The conclusion is based on radiocarbon estimates from the sampled sharks, not on a specimen whose age was tracked from birth.
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Why the estimate has a broad margin of error
The largest sampled shark, a 502-centimetre female, was estimated to be 392 ± 120 years old. The ±120 years is the extent of the study’s 95.4% probability range, so the result covers a very broad span of plausible ages. The same analysis estimated sexual maturity at 156 ± 22 years and concluded that the species’ lifespan is at least 272 years.
Those figures are model-based estimates. The 2025 Canadian assessment by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) says the age estimates have not been validated by an alternative method. It also notes that uncertainty in deep-ocean radiocarbon levels complicates the calculation of when a shark was born. “Centuries old” is therefore a sound description of the evidence, but a precise claim that an individual lived exactly 392 years is not.
| Measurement | Reported result | What it means |
|---|---|---|
| Largest shark in the study | 502 cm total length | The biggest of the 28 females sampled |
| Estimated age of that shark | 392 ± 120 years | 95.4% probability range; a model estimate, not a known birthday |
| Estimated age at sexual maturity | 156 ± 22 years | Approximate age when reproduction begins |
| Inferred minimum lifespan | At least 272 years | Lower-bound conclusion from the 2016 analysis |
Why such a long life is biologically plausible
Cold-water ecology and slow metabolism
Greenland sharks inhabit cold, deep northern waters. NOAA presents a slow metabolism adapted to cold water as one possible explanation for their longevity, not as a proven single cause. A careful interpretation is that the species’ cold-water ecology is associated with slow growth and long life, while the biological mechanisms that produce a lifespan of several centuries remain an active research question.
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NOAA’s public explainer reports growth of less than 1 centimetre per year. A limited mark-recapture estimate summarized by COSEWIC likewise puts annual growth at or below 1 centimetre. This is an approximate rate reported for the species, not a promise that every shark grows at exactly the same speed during every life stage. Even at that pace, reaching several metres requires many decades.
Reproduction arrives very late
An estimated maturity age of 156 ± 22 years means a shark may spend more than a century growing before it can reproduce. Long generation times can stabilize a population under natural conditions, but they also make recovery from added mortality exceptionally slow. Removing a mature animal can mean losing an individual that took generations of human lifetimes to replace.
What directly threatens Greenland sharks
Fisheries bycatch is the clearest documented threat
Greenland sharks are caught unintentionally in trawl, demersal longline and gillnet fisheries throughout their range. COSEWIC estimates at least 3,500 sharks are taken as fisheries bycatch worldwide each year. For Canadian fisheries, the assessment estimates 1,688 to 2,208 sharks annually. These are estimates built from incomplete reporting; COSEWIC cautions that poor bycatch data may mean the real total is higher.
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Bycatch can be harmful even when fishers do not retain the shark. The assessment says post-release survival of discarded Greenland sharks is largely unknown. Handling, time on the gear and injuries can all matter, but there is not enough evidence to convert every released animal into a known survival outcome. NOAA summarizes the conservation priority plainly: “Reducing bycatch is critical in conserving this unique species.” The statement appears on its Greenland shark explainer.
Some sharks are deliberately targeted
Bycatch is not the only fishing interaction. COSEWIC reports that Greenland sharks are also targeted in small-scale fisheries in Iceland and Greenland. The available assessment does not provide a precise global catch total for directed fishing, so it should not be combined with the bycatch estimate as though the two figures measured the same thing.
| Pressure | Evidence and scale | What is established about population effects |
|---|---|---|
| Incidental fisheries capture | Reported in trawl, demersal longline and gillnet fisheries across the range; at least 3,500 estimated worldwide each year and 1,688–2,208 in Canadian fisheries | Direct mortality risk is documented, but totals are incomplete and post-release survival is largely unmeasured |
| Directed fishing | Small-scale fisheries in Iceland and Greenland target the species | The cited assessment does not provide a precise global directed-catch total |
| Climate-related habitat change | Arctic warming may alter sea-ice extent and other habitat conditions | Possible effects on distribution, fitness and population dynamics are recognized, but no numeric population impact is established |
Why slow life history magnifies fishing risk
Fishing pressure does not affect a rapidly reproducing fish and a Greenland shark in the same way. A species that grows at roughly 1 centimetre or less per year, matures after about 156 years and has a long generation time has few opportunities to replace lost adults quickly. That combination makes even apparently modest annual removals important over decades.
It is not possible to turn the available figures into a single, reliable global decline percentage. COSEWIC reports no population estimate for Canadian waters and says global decline estimates vary widely because key life-history and mortality inputs are uncertain. The sensible conclusion is risk-based: the species’ biology gives it little demographic capacity to absorb sustained mortality, even though the exact size and trend of every population are not known.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Could climate change add another pressure?
COSEWIC identifies Arctic climate change as a potential threat. Changes in sea-ice extent and other ocean conditions could alter where Greenland sharks can live, how much suitable habitat is available, their physical condition and the dynamics of local populations. These are plausible pathways, not quantified demonstrations that climate change has already caused a particular decline.
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Conservation status and protections
Canada’s 2025 designation
In May 2025, COSEWIC designated the Greenland shark as Special Concern in Canada. Canadian fisheries rules and licence conditions prohibit retention and require sharks to be released alive with as little harm as possible. Those measures apply to Canadian fisheries; they should not be presented as a worldwide rule.
Global context
COSEWIC’s report notes that the species was assessed as Vulnerable by the International Union for Conservation of Nature (IUCN) in 2020. This is a global assessment cited by the Canadian report, not a replacement for current, region-specific population monitoring.
What effective conservation needs to address
- Improve reporting of Greenland shark interactions so bycatch estimates cover more fleets and gears.
- Reduce capture and physical damage in trawl, longline and gillnet fisheries, with handling practices designed for live release where release is required.
- Measure post-release survival instead of assuming that every discarded shark survives.
- Continue research on abundance, movement, age validation and reproduction so population models use better inputs.
- Track habitat changes in Arctic and North Atlantic waters without treating a potential climate effect as a measured decline until evidence supports that conclusion.
What we can—and cannot—say about their age
The strongest defensible statement is that Greenland sharks are among the longest-lived vertebrates known, with evidence for lifespans lasting centuries. The radiocarbon method explains how scientists reached that conclusion despite the absence of usable vertebral growth bands. It does not provide an exact birth certificate for each shark, and the Canadian assessment has identified no independent validation of the published age estimates.
The 392 ± 120-year result should therefore be read as an unusually old central estimate with substantial uncertainty. The maturity estimate of 156 ± 22 years and the reported growth rate below 1 centimetre per year independently reinforce the picture of an exceptionally slow life history. Together, those traits explain why preventing avoidable fishing mortality is more urgent than waiting for populations to rebuild on their own.
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