Are There any Venomous Sharks?

Are There any Venomous Sharks?

The ocean presents many threats to swimmers and divers, not least of all drowning. But of all the dangerous animals in the water, the shark is the most iconic and feared.

Something about a giant predatory fish really taps into our primal fears. However, large teeth aren’t the only thing to worry about.

Many ocean animals use venom or other toxic substances as a defense – or as a means of attack – and these can be equally dangerous. Anemones are well known for their stings, but fortunately, they stay mostly adhered to rocks.

Lionfish, scorpionfish, and some particularly ugly flatfish can give a nasty and potentially lethal sting to an unsuspecting beach-goer in some parts of the world.

Then there are rays, close cousins of sharks. The stingray is the most well-known for its venom, but are there any venomous sharks? 

Some sharks in the dogfish and bullhead orders of sharks are known to be venomous to some degree. Typically, these sharks have spines in the dorsal fins that can inject venom as a defense and don’t seem to use them aggressively unless provoked. 

Which Sharks are Venomous?

As mentioned, there are two orders that have been found to contain venomous sharks.

These are the dogfish – or Squaliformes – and the horn sharks – or Heterodontiformes.

It’s unknown exactly how many species are considered venomous, and sharks from other orders will likely be discovered to be venomous in the future. So far, the list of venomous sharks is already quite long, but here are a few examples.

  • Lantern sharks – These sharks aren’t just venomous; they also glow in the dark! They’re in the dogfish (Squaliformes) family and can be so tiny they fit into your hand.
lanternshark
Lantern shark
  • Gulper sharks – These are vulnerable, deep-water sharks heavily affected by overfishing. They’re small, schooling sharks that mostly feed on small fish and crustaceans.
gulper shark
Gulper shark
  • Small-eye Pigmy sharks – another tiny little friend found in exceptionally deep waters in Asia. Again, it’s in the dogfish order, so it’s not surprising it sports some mean spines in its dorsal fin.
  • Port Jackson sharks – This funny-looking fish is about the size of a puppy and feeds on crustaceans. It’s a type of horn shark, and the venomous spines help juveniles stay safe in the presence of predators.
port jackson shark
Port Jackson shark

It’s only recently been discovered that some of these sharks are indeed venomous, so word hasn’t made it out far yet, but expect a significant increase in common knowledge on the topic following this 2016 report. For a full list of the species surveyed, download the supplementary data from the bottom of the report page.

Which Shark is Toxic?

Venom itself is a form of toxin – one that is injected, as opposed to absorbed through the skin or swallowed, like a poison.

So, all of the venomous sharks are also toxic, by definition.

But there are other ways sharks can be toxic to humans, and this applies to a lot of the different types of fish in the ocean too.

Sharks are very tough animals; they can handle high amounts of toxic chemicals in their food and water. What this means is that toxins from human pollution can accumulate in the tissues of a shark in high amounts. When people eat shark meat, it can pass on dangerous levels of these toxins to the person eating it.

Coal combustion creates man-made mercury pollution that reacts with the environment and creates an exceptionally toxic form of mercury. Many of the shellfish and fish that we eat contain unsafe levels of these toxins, including sharks.

Pesticides such as DDT make their way into the ocean too, and these can be toxic to sea life and humans, potentially causing cancers.

Because of human pollution, almost all life in the ocean has the potential to be toxic. Burning coal for energy creates an abundance of harmful pollutants that enter the water and infect sharks, fishes, and shellfish to the point where eating them can be harmful to humans.

The most toxic shark is reportedly the Greenland shark!

But this isn’t because of pollution. The Greenland shark holds on to crazy amounts of urea to allow it to hold onto its water, and for this, it needs a stabilizing molecule called TMAO to protect its proteins from the damaging effect of the urea. This TMAO is toxic to humans in such large amounts.

Conclusion

So, it seems like the list of venomous sharks is increasing rapidly!

So far, it’s mostly limited to the dogfish and the horn sharks, but considering how little we know about sharks overall, it isn’t hard to imagine this changing in the near future if they’re around long enough for us to find out.

As for toxicity, sadly, many of the animals in Earth’s waters are afflicted with heavy metals and other human-influenced pollutants, making them unwell and unsafe to eat.

Having said this, the Greenland shark is toxic enough without help from humans.