For most people, their fear of sharks comes from being bitten by the animal’s sharp teeth. But did you know that certain species have evolved the ability to deliver a painful poison?
The most well-known example of a venomous shark, the spiny dogfish, has two venom-producing spines, one in front of each dorsal fin. If captured by a predator, the dogfish can raise its spines by arching its back and pushing them into the attacker to deliver a powerful self-defense weapon.
This article will show you what a venomous shark is, starting with the spiny dogfish and discovering how dangerous it is to humans. We’ll also find out what other venomous shark species there are.
We’ll finish by looking at sharks that aren’t venomous but have toxic flesh that could be deadly if consumed.
Is the Spiny Dogfish a Venomous Shark?
So, what is a venomous shark?
Typically, when we think of a venomous animal, we imagine a snake or perhaps an insect that uses a bite or a stinger to inject a toxin made in specialized glands or cells into its victim.
Is a spiny dogfish shark venomous? Yes, it produces venom, but the delivery method differs from more familiar venomous species.
Instead of a sting or sharp fangs, the spiny dogfish (Squalus acanthias) has a spine in front of each of its two dorsal fins that it uses to produce and deliver poison.
The two spines are modified scales that have evolved for a unique purpose. Each spine is covered in grooves containing specialized glands that produce venom.
So, while the dogfish may not deliver venom with a bite or a sting, it manufactures its own venom and has the means to use it.
Why Is the Spiny Dogfish Venomous?
The spiny dogfish, also known as the spurdog, piked dogfish, or mud shark, isn’t the biggest shark in the world. They reach a maximum length of about 1.4 meters (4.5 feet) and weigh only about 10 kg (22 pounds) when fully grown.
While the dogfish likes to hunt fish, squid, jellyfish, crab, sea cucumber, and shrimp, it is itself the target of much larger fish, including many of the bigger predatory sharks, in addition to seals and orcas.
Why are some sharks venomous? Some sharks, including the spiny dogfish, have developed the rare ability to produce venom for self-defense.
When the spiny dogfish feels threatened, perhaps when approached or even grabbed by the mouth of a predator, it will arch its back to raise the two special spines away from its body.
The spines are sharp enough to pierce the flesh of an attacker, and the pressure applied to the grooves on them causes the venom to be released.
If the spine’s presence didn’t prevent the attack in the first place, the sudden pain in the mouth from the venom is usually enough to cause the predator to release the dogfish.
Depending on the severity of any injuries it received, the dogfish may be lucky enough to swim away and escape.
So, while the dogfish may not have the most enormous teeth of any shark, its two venomous spines give it an advantage when it comes to protection from attack.
How Dangerous Is the Venom of a Spiny Dogfish?
To an attacking predator, like a bigger shark, bony fish, or seal, the venom from the spiny dogfish is painful rather than deadly.
The discomfort might ward off the predator, but the venom probably won’t have long-lasting effects.
On the other hand, the shark’s spines themselves could cause a reasonably significant injury depending on the attacker, which may cause physical damage or infection inside a relatively delicate mouth.
Humans typically come into contact with spiny dogfish when they catch one while fishing. In this case, care must be taken when handling the shark to avoid getting stung while landing the fish.
Fortunately, dogfish venom isn’t deadly to humans. However, it can cause severe pain and swelling, and the wound itself can get badly infected by bacteria found in seawater.
How To Treat a Spiny Dogfish Sting
If you, or someone with you, is unfortunate enough to get stung by a spiny dogfish, there is some straightforward first aid to follow to reduce pain and help prevent infection.
- Heat the wound by immersing it in hot (not scalding) water for at least fifteen minutes. The heat can break down the venom and reduce the severity of pain and inflammation.
- Ensure the wound is cleaned thoroughly with clean, fresh water and apply antiseptic.
- Seek medical attention when possible. The victim may require treatment with anti-inflammatories and antibiotics.
Are Dogfish Poisonous?
While the venom in the spines can be painful, dogfish flesh is not poisonous to eat.
In fact, while dogfish are not that commonly eaten in the United States, they’re very popular in Europe and Asia and have a flesh similar to that of meaty white fish.
In the United Kingdom, dogfish are known as rock salmon and are eaten as an alternative to cod in fish and chips.
In Germany, the shark is popular as a smoked fish, and in Korea, spiny dogfish are eaten in numerous delicious dishes.
Preparing the fish properly after catching it is essential so the flesh doesn’t go bad.
Gutting and bleeding the fish entirely and getting the flesh on ice immediately means that bacteria can’t produce ammonia, which spoils the taste.
Where Do Spiny Dogfish Live?
Spiny dogfish are bottom-dwelling sharks generally found at depths of around 50–149 meters (160–490 feet), although they’ve been recorded as deep as 914 meters (3,000 feet).
The Atlantic spiny dogfish (Squalus acanthias) lives in temperate coastal and off-shore waters of the northern and southern Atlantic oceans and in the southern Pacific.
A separate species, the Pacific spiny dogfish (Squalus suckleyi), lives in the northern Pacific.
Why Are Dogfish Called Dogfish?
There are several suggestions as to how these sharks got the name dogfish.
One of the most popular is that fishermen had watched groups of sharks hunting smaller fish with tenacity and endurance that reminded them of a pack of dogs.
Other explanations suggest that the sharks look a little like dogs in appearance, with broad heads and blunt noses reminiscent of a bulldog.
Are There Other Venomous Sharks?
The spiny dogfish is one of the world’s most abundant shark species. But are there other venomous sharks?
The vast majority of the ocean’s sharks aren’t venomous. They rely on the more traditional method of having mouths filled with sharp teeth to defend themselves.
However, the other 29 species of dogfish (Squaliformes) and the nine horn sharks (bullhead sharks of the family Heterodontidae), such as the common Port Jackson Shark, have venomous spines.
Like the spiny dogfish, the other venomous species only use their spines as a defense mechanism when they feel threatened.
Is the Greenland Shark Venomous?
The Greenland shark (Somniosus microcephalus) isn’t venomous. However, its flesh is poisonous if not prepared correctly.
This unique shark has evolved to live in the deep cold waters of the North Atlantic and Arctic Oceans. Its tissues contain high levels of the toxic chemical trimethylamine N-oxide to allow it to survive in such a harsh environment.
However, the meat is a traditional delicacy known as kæstur hákarl amongst the Inuit communities of Iceland.
The shark’s flesh is made safe by boiling it repeatedly in multiple water changes, followed by a careful drying and fermenting process involving burying the meat in the ground.
Indeed a recipe best left to the experts.
“Venomous” typically describes animals with a specialized delivery mechanism for poisons, and the most familiar species, such as snakes and spiders, use their venom to subduing prey.
However, the unusual sharks, including the spiny dogfish equipped with venom, don’t use it for the attack.
These sharks have evolved with venomous spines to defend against predators or threats.
It’s important to note that out of the approximately 500 species of shark, only about 40 have developed venomous spines.
The sting from the spine of the spiny dogfish can cause pain, swelling, and other reactions in animals or humans that come into contact with them.
Thankfully, the toxin is not fatal to humans, although first aid treatment is required to prevent pain and infection.
Most injuries occur due to accidental contact with the particular species, either when fishing or perhaps wading in shallow waters where they live. So, taking suitable precautions to protect yourself against a painful sting is always a good idea.
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British-born Dan has been a scuba instructor and guide in Egypt's Red Sea since 2010.
Dan loves inspiring safe, fun, and environmentally responsible diving and particularly enjoys the opportunity to dive with sharks or investigate local shipwrecks.
When not spending time underwater, Dan can usually be found biking and hiking in Sharm's desert surroundings.