Sharks seem almost indestructible. They’re highly disease-resistant, and some species, like the Greenland shark, live for hundreds of years. So how do sharks die?
Sharks are not invincible, however, and die just like any other living thing. Sure, the great white heals quickly and effectively and has a mechanism that protects it against “autoimmune disease (like cancer) and age-related illnesses.”
On the other hand, it doesn’t have any way of protecting itself against its number one predator – the human.
How Do Most Sharks Die?
Each year, humans kill an estimated 100 million sharks. Many blame the shark fin industry for the vast majority of those deaths, but by-catch, over-fishing, culling, and habitat destruction all play a significant role in the shark’s demise.
Very few sharks die of natural causes, and non-human predators kill only a handful. Some of the main contributors to shark deaths are:
#1 Over-fishing
Shark finning is a cruel practice that sees commercial fishing operations remove the fins of living sharks before throwing the rest of the animal back into the ocean, where it dies a slow and painful death. Although the demand for shark fins endangers the lives of many sharks, according to David Shiffman, a postdoctoral researcher at Arizona State University, it’s “not the biggest threat.”
Overfishing, including “reported and unreported landings, discards and discards [by-catch], and shark finning,” accounts for at least 100 million shark deaths a year. Many believe these statistics to be overly conservative.
In 2013, researchers assessed global catch statistics using an analysis of the average shark’s weight to estimate the total annual mortality rate. They surmised that “between 63 and 273 million sharks” were killed each year.
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Many fishing operations target sharks for their fins. These are used to make the Chinese dish shark fin soup, which is served at celebrations and events as a status symbol and delicacy. The shark meat trade has expanded rapidly in recent years, encouraging commercial fishing boats to kill even more sharks.
There’s also a demand for shark cartilage and oil, both of which are rumored to have natural anti-carcinogenic and anti-inflammatory qualities. Although there is no scientific proof t support these claims, the value of international trade in shark products is around $1 billion per year.
Even with an estimated global population of over a billion, this has a significant impact on the world’s shark population. The shark’s slow reproduction means that some shark species struggle to recover, rendering our current shark fishing practices unsustainable.
#2 Shark By-catch
More sharks may be killed by by-catch every year than are actively targeted by the fishing industry. Along with dolphins, rays, and other fish, millions of sharks are incidentally caught in bottom trawl, gillnet, hook-and-line, and longline fisheries. Some are retained and sold for their fins, oil, and meat, while others are discarded. None survive the experience.
A few years ago, a study of juvenile white sharks in southern California concluded that juvenile mortality “mainly resulted from interactions with fisheries, whereas natural mortality was relatively rare.”
#3 Culling
A few countries have actively tried to reduce the number of shark attacks on humans by actively reducing the shark population. Using baited drum lines and “shark nets,” they target and kill sharks that are perceived to be a threat to humans. Great whites, tiger sharks, and bull sharks all get entangled in the shark nets where, unable to swim, they drown.
The impact of shark culling is negligible compared to the fishing industry’s by-catch. Statistics suggest that the Queensland shark control program catches around 15 great white sharks per year, compared to the 130 tonnes of great white Australia’s commercial shark fishing industry kills annually.
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How Do Sharks Die of Natural Causes?
As we mentioned earlier, sharks can recover from horrific injuries and have a natural defense against many age-related illnesses.
Nevertheless, a handful of sharks die of old age or at least get so old that they lose their faculties until they can no longer feed or compete for food. Some may starve to death due to a loss of vision, while others may struggle to fend off disease as the result of a weakened immune system.
Just as sharks abandon their pups as soon as they’re born, their offspring won’t take care of them as they age. Instead, the elderly shark gradually loses its ability to hunt or fight off infection and other predators and dies.
Can Sharks Die of Old Age?
A shark won’t simply reach a certain age and then keel over any more than a human does. Nevertheless, as a shark ages, its body stops functioning as efficiently, making it increasingly difficult for the animal to survive.
As competition is fierce amongst the apex predators of the oceans, an aging shark that can’t swim as fast as its competitor, or fight as ferociously for its prey, will battle to survive.
What Happens When a Shark Dies?
Once dead, the shark’s body drifts to the bottom of the ocean, where it completes the cycle of life by providing nourishment for scavengers, including deep-sea sharks.
What Will Kill a Shark?
Besides humans, very few animals prey on the shark. Every shark species has some cannibalistic tendencies, so each one is more likely to kill each other than die by another’s jaws.
The killer whale or orca is the only animal known to predate the great white. The first attack was reported in 1997 when an orca killed and started to ingest a 3-4m white shark.
Over the past three years, two orcas in South Africa have honed their hunting abilities and can seemingly remove the livers of great white sharks with surgical precision, killing their victims in the process.
Do Sharks Eat Sharks?
Sharks do eat each other and, according to Professor Mark Meekan of the Australian Institute of Marine Science, “Shark-on-shark predation is a fundamental trait.”
Pups and young sharks purposefully utilize shallower waters so they can avoid becoming a meal for one of their elder relatives. Similarly, large shark species will prey on smaller ones.
In some dramatic encounters, two sharks of similar size will attack one another, as in this video, or several will gang together to perform a brutal attack on an individual from a different species.
For some species, cannibalism starts before they’re even born. As we discussed in our article about the life cycle of sharks, some shark species cannibalize their siblings while still in the womb.
The sand tiger shark only has two pups, despite producing numerous eggs. That’s because these pups eat everything else, from unhatched eggs to sibling embryos.
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Do Sharks Die From Fighting?
When you’re an apex predator, you need to be the fastest and strongest. Sometimes, the only way to prove that is by entraining into combat with your competitors. Sharks do sometimes die in fights, both with other shark species and when fighting off predators like the orca.
This blacktip shark managed to survive for a full 20 minutes before succumbing to the extensive injuries inflicted on him by a gang of bull sharks.
Sharks sometimes bite off more than they can chew. In March last year, a Mako shark was found dead on a beach in Mexico.
The cause of death was obvious – it had a 20 cm poisonous stingray barb protruding from its snout.
Although Mako sharks aren’t commonly known to hunt stingrays, they are opportunistic feeders with a diverse diet. This one clearly met its match.
Do Sharks Abort Their Babies?
A study released last year revealed that 24% of 88 different species of sharks and rays either abort their pups or undergo a premature birth once captured.
This “capture-induced parturition” occurs even when the shark is subsequently released.
As sharks have such long gestational periods, this level of capture-induced abortion has a significant impact on their population, and their reproductive potential.
How Do Great White Sharks Die?
Great white sharks can live for up to 70 years if they manage to avoid human interaction for that long.
Great whites get caught in shark nets, tangled in the equipment used by commercial fishing operations, killed for their fins, and culled because of the threat they present to humans.
Orca may also target them on occasion, and some may even fall foul of a stingray from time to time.
How Do Whale Sharks Die?
Mature whale sharks are the largest fish in the sea, measuring over 30 ft long and weighing more than 15 tons.
While their enormity protects them against most predators once they reach adulthood, as youngsters, they come under threat from some of the ocean’s apex predators, including great whites, tiger sharks, and orcas.
Like the great white, whale sharks sometimes get tangled in fishing nets and subsequently drown or suffocate. In some places, like China, they are still hunted and killed for their meat, fins, and skin, despite the practice being illegal.
How Do Hammerhead Sharks Die?
Despite their intimidating appearance hammerhead sharks have numerous enemies, including the great white, orca, and tiger shark.
The biggest enemy of all, however, is the human. The shark fin industry targets hammerhead sharks for their large fins. They also get caught in commercial fishing nets and lines, with few surviving the experience even if they’re subsequently released.
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Why Do Sharks Die in Captivity
Some shark species do fine in captivity, but others find the experience intolerable. The biggest shark you’ll generally see in a public aquarium is the sand tiger shark. There are several reasons for this:
- The hardiness of the sand tiger shark enables it to adapt to a different environment and acclimatize to life in captivity.
- The sand tiger shark is found in most parts of the world, making it easier to acquire and transport
- The sand tiger shark can live relatively harmoniously alongside other large sharks and fish, including the whitetip reef shark.
On the other hand, great white sharks are almost impossible to keep in captivity. Some refuse to eat while others “bash their heads into the tank’s walls.”
Experts believe that stress and injury contribute to great white aquarium deaths, and although aquariums sometimes release stressed sharks back into the wild, their subsequent chances of survival are unknown.
The most successful attempt at keeping a great white shark in captivity happened in Monterey Bay Aquarium in 2004.
A female great white accidentally caught in a commercial fishing net was moved into the aquarium’s Open Sea exhibit and survived there for 198 days.
The shark grew and ate well but became so aggressive towards the other sharks in the exhibit that she was subsequently released.
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Conclusion
Sharks have evolved to become one of the most resilient creatures on earth.
They can live for hundreds of years, have a natural ability to fight off cancer and other illnesses, and are such effective predators, that they have few natural enemies.
Statistics suggest that humans kill more sharks each year than anything else, and that your average great white is more likely to die at the hands of a commercial fishing operation than of illness or old age.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.