The life span of a shark is hard to measure. They don’t tend to celebrate their birthdays, and even if they did, some of them live so long that anyone who started counting would be long dead before they reached middle age.
Sharks in captivity can be well documented, but captivity itself affects the lifespan of animals in different ways, so it’s not an accurate representation of their natural limits.
Sharks like the great white die very quickly in captivity, and others are thought to potentially live longer in captivity than in the wild.
In general, however, most sharks don’t survive for as long in captivity as in the wild.
But exactly how long do sharks live?
No great white has lasted more than six months in captivity, though they are thought to live longer than 70 years in the wild. The Greenland shark holds the record for longest living shark, and estimates for its lifespan range from 250 to 500 years!
But it’s difficult to measure, and sharks are notoriously elusive when it comes to giving up their secrets. So, let’s delve a little deeper into what we know.
Measuring Shark Longevity
When you’re curious about the age of a tree, you can cut it down and count the rings.
This, of course, immediately limits the age of that particular specimen, as, unfortunately, is the case with sharks.
Until recently, scientists used this method to estimate a shark’s age by counting calcified ‘growth rings’ in the vertebrae of dead sharks.
But these rings don’t increase at a regular, annular rate like in trees, and they tend to present in different concentrations at different locations along with the shark, so it’s hard to know for sure how old a shark is from this method alone, and this method has been shown to be inaccurate in some species.
Between 1945 and 1963, world powers were testing exciting new ways to murder one another on a huge scale. Unprecedented nuclear explosions from bomb tests filled the atmosphere with a measurable doubling of a particular isotope of carbon. As carbon-based life forms, all animals, including sharks, have now got a record of this isotope in the building blocks of their cells.
Scientists figured out how long it takes for the body to change its ratio of this carbon isotope, and from that, can estimate the ages of sharks by measuring how much of it they have left in their cells.
In some cases, this bomb pulse dating has replaced growth ring counting as a more accurate way of estimating the ages of shark species.
Incidentally, this is how we get the idea of how old Greenland sharks can live.
But enough about life, let’s look at death! If sharks can live for so long, what kills them?
How do Sharks Die?
As hard as it is to get data on how sharks live, it can be even harder to get data on how they die.
Imagine you’ve got a tag on a shark, and then suddenly it disappears – the shark is probably dead, but how? In some cases, you might find your tag inside a bigger shark or orca, and then you can make an educated guess, but for the most part, it’s a total mystery.
There are some causes of death that we do know about, though. Let’s break it down by species and look at some of the things that kill the most popular sharks:
Is has been established that killer whales will hunt great whites. In fact, they’re about the only animal scary enough to predate on an adult white shark. Other factors that lead to the premature demise of whites are captivity, fishing, gill injuries from nets or cages, and in some rare cases, bacterial infections of the brain.
Being somewhere in the middle of the shark size scale, there is always a bigger fish for a hammerhead. And great whites, tiger sharks – even larger hammerheads will all chow down on a pup.
These beautifully weird sharks are thought to live up to about 30 years if they aren’t predated upon, but the other sharks, orcas, and a brutal shark finning and fishing industry all contribute to killing them before that.
Bull sharks are one of the largest predators in the ocean, but they still start off life pretty tiny. At least tiny enough to get eaten by tiger, sandbar, and other bull sharks. These sharks are one of the few who can handle freshwater and, as such, have one predator that sharks don’t usually worry about – crocodiles! These sharks are thought to live upwards of 30 years if they can make it that long.
Tiger sharks are another large predator that only has one animal above it in the food chain – the killer whale. Killer whales have been known to flip over a tiger shark and tear it to pieces. Like most sharks on this list, they’re also a casualty of the fishing industry and shark finning practices.
They have been recorded living as long as 27 years but are estimated to live up to 50
Greenland sharks live in the arctic. Killer whales visit the arctic. Killer whales kill great whites, and great whites are much faster and bigger than Greenland sharks. To me, it’s a simple calculation, although there are no known reports of Greenland sharks being predated upon by anything.
As expected, they are killed by fishers, but if they can avoid people for long enough, it’s thought that they might live for up to and above 500 years.
These graceful giants are typically too big to eat as adults, but as juveniles, sharks and blue marlins will have a go at them. As usual, orca and humans will also kill them, and they’re hunted for meat in some places. These are slow-moving, long-lived sharks with a life expectancy of up to 100 years.
How do Most Sharks Die?
By far, the most common cause of death in sharks is humans. A statistic that has been kicking around for over 12 years is that humans are responsible for at least 100 million shark deaths per year, and it’s likely to have increased substantially since then.
Common villains are the shark finning industry, which contributes to tens of millions of these sharks being butchered while still alive and then dumped back into the sea to die.
While this is a particularly disgusting practice, it’s not the full story.
Commercial fisheries everywhere in the world are responsible for overfishing and the depletion of the world’s oceans. Fish of nearly every kind are declining globally, and even self-proclaimed ‘sustainable’ methods like line fishing put a serious dent into shark populations.
The stress of being caught on a line and dragged through the water is often too much for a shark.
Even when released, up to 71% of blacktip and spinner sharks will die. This is also true for sport fishing, so catch-and-release fishing of any kind is a threat to shark populations.
Large nets are responsible for a significant portion of by-catch – unwanted collateral damage of commercial fishing methods. Sharks are commonly caught up in these nets and can suffer gill injuries, causing them to suffocate even if they make it back into the water alive.
Tuna fishing, as well as shrimp and small fish catching methods, are tremendously hazardous to sharks.
In Europe alone, nearly a third of Mediterranean shark species are fished close to the level of extinction.
However, the European Parliament has been gradually revising its control systems for fisheries to control this.
Do sharks die of old age?
In captivity, sharks are known to die of old age, but this process is no doubt accelerated by the stress of the conditions in which they live.
Sharks are highly specialized creatures with a large territory that cannot be adequately replicated in captivity.
Most sharks die young in captivity, but they may not have it much better in the wild.
Animals in the wild rarely die peacefully in their beds. The moment they slow down or get tired, they’re usually picked off by something healthier than they are.
This is no doubt true for sharks, and while some may manage to find peace in their final moments, the chances of anyone being around to document it are slim.
How do nets kill sharks?
Nets can be a particularly gruesome way to go.
Sharks caught in nets can have their gills damaged or blocked, essentially causing them to suffocate. A handful of pelagic sharks can’t breathe unless they’re moving, so being caught in a net even without damage is a death sentence.
Most times, however, the delicate tissues of the gill are torn and damaged, and the shark can’t supply itself with enough oxygen.
In some cases, such as in Australia, nets are designed to protect swimmers. These gill nets capture the shark and are designed to entangle and kill it. In this case, humans choose to enter the shark’s habitat for recreation, with lethal consequences to the shark. Often the nets are ineffective.
How do sharks die after finning?
Shark fin soup is a delicacy in China. The industry is enormous, and the toll on sharks correlates with this. It’s estimated that 73 million sharks are killed by the finning industry alone, and it’s not a kind death.
The sharks are dragged on board boats, where their fins are sliced off, and they are thrown back into the water. If they survive this, many will suffocate or lie on the sea bed until they’re eaten alive by another predator.
This practice, along with the estimated 50+ million by-catch deaths from the rest of the fishing industry, is responsible for 100 shark species hurtling towards extinction.
Do sharks die if they stop swimming?
It’s often repeated that a shark can’t stop swimming or it will die.
This isn’t quite a myth, but it’s not entirely true either.
All sharks breathe through a process called ram ventilation. This is where the motion of the shark forces water through the gills like air into an engine.
A few long-distance pelagic sharks breathe via ram ventilation alone, and these are called obligate ram ventilators. Just over 20 species of sharks have this restriction and can’t stop moving.
Most of the 400+ species of sharks breathe via buccal pumping, which involves gulping in water via the mouth and pushing it over the gills.
How Can We Protect Sharks From Fishing?
A 2021 European report based on the shark fishing situation around Spain and Portugal offers some illuminating statistics that apply to fishing industries and consumers everywhere.
The report makes a series of key recommendations for the fishing industry.
Still, it conveniently avoids placing much of the responsibility on consumers, recommending only that they avoid eating shark products – something that most people do already.
This lack of responsibility is exactly what keeps the fishing industry in power; as long as consumers are buying fish indiscriminately, fisheries will continue to use unsustainable methods to acquire it.
Of course, legislative change is needed, but from a consumer’s perspective, the best thing we can do to protect sharks is to move away from unsustainable seafood, demand responsible labeling for seafood products, and speak up on behalf of sharks and rays.
Sharks have been around for 450 million years. And as far as we know, they can live for up to 500 years!
Some have few natural predators, but many more are eaten by killer whales, other, larger sharks or die in captivity.
But the vast majority of premature shark deaths come from the fishing industry.
Fueled by consumer demand, fishing practices have become totally unsustainable and are wiping our oceans clear of many fish species, including sharks.
Around 100 species of shark are now in rapid decline and may not be around for much longer.
Shark finning is a significant and grotesque contributor to this demise, but as seafood consumers, we are all complicit.
Destructive fishing practices continue to go unchecked, and the public must inform themselves and spread the word.
Demand better treatment of our oceans and help protect their ancient inhabitants!