You might think an animal that sits totally still on the seabed or coral reef doesn’t pose much of a threat but, when it comes to stonefish, you’d be wrong.
These ambush predators are known as the most venomous fish on the planet. They’re not going to come after you but, if you don’t spot one and touch it by accident, you’re going to know about it. They can deliver a serious sting that can even be fatal.
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What are stonefish?
In short, the most venomous fish on the planet. Stonefish are masters of disguise known for their incredible ability to hide in plain sight, using camouflage to conceal themselves.
This lie-in-wait strategy is how they hunt prey but it can also be the cause of injuries to humans. Although stonefish don’t attack people, someone who doesn’t see them hiding out and accidentally touches one of their 13 venomous spines will be dosed with a painful – and potentially deadly – injection of toxins.
How big are Stonefish?
They are up to around 40cm and weigh around 2kg
What do they look like?
Unlike many colourful reef fish, these ugly lumps aren’t going to win any beauty contests.
Admittedly, they’re so well camouflaged that if you’re diving or snorkelling on a rocky reef, you might not even spot them at first. But look carefully and you might notice that what you thought was a lumpy rock is staring straight back at you.
Unlike scorpionfish – which look similar in many ways to stonefish – these hulking round lumps don’t have a discernible ‘fishy’ shape. Instead, their large downturned mouth and round body makes them look like someone drew a miserable face on a boulder.
Stonefish also have bumpy grey, green or brown skin, often covered in warts and lumps, to help them blend even more seamlessly into the uneven reef around them. This is probably how they got the unflattering nickname “warty ghoul”.
Where do they live?
Reef stonefish are found in the tropical waters of the Indo-Pacific, the Red Sea and the Great Barrier Reef. These masters of disguise often loiter camouflaged into the reef, rocky seabed or buried in the sand with just their venomous spines, eyes and mouth peeping out (ready to pounce on hapless prey).
What do they eat?
These predators eat small fishes and crustaceans, as long as they get close enough to allow the stonefish to strike.
How do they hunt?
Like other ambush predators, their hunting strategy is… to do nothing. The stonefish waits in total stillness relying on its natural camouflage to help it disappear almost entirely into the reef. Then, it waits – sometimes for hours – until a tasty morsel swims by.
When its prey comes close enough, the stonefish launches an attack. It opens its huge mouth wide and gobbles down its victim in one gulp. This can all happen in a fraction of a second.
How do they reproduce?
Stonefish tend to be solitary animals but they do come together to reproduce. Females lay their eggs on the seafloor for the males to fertilise. When the babies hatch, they are fully independent.
Are they dangerous to humans?
Yes, very – but only if you’re not careful as these animals don’t tend to be aggressive towards humans. Their venomous spines are purely for self-defence.
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There are five known species of stonefish. The two that are best studied – the estuarine stonefish (Synanceia horrida) and reef stonefish (Synanceia verrucosa) are both highly toxic.
“Stonefish possess up to 15 dorsal spines, each with two venom sacs containing a total 5–10 milligrams of venom,” according to the Guinness World Records’ website. “S. horrida venom has an LD50 rating as low as 0.4 micrograms (μg) per kilogram, thus a lethal human dose can be delivered easily by only one or two spines.”
If you touch or step on one of these spines, the pressure will cause the stonefish to release a potent toxin. The pain is said to be excruciating and victims may also experience paralysis, difficulty breathing and cardiac arrest. If you believe you may have been stung by a stonefish, call for medical help without delay.
Despite the deadly nature of stonefish toxin, fatalities are rare. These fish don’t attack humans but you can protect yourself from stings by never approaching or touching marine life, looking carefully when swimming on or exploring rocky reefs, wearing suitable shoes when walking in the shallows and doing the “stingray shuffle” to prevent yourself from stepping on a buried stonefish (or stingray for that matter).
Are they under threat?
Stonefish are not known to be under threat and are categorised as a species ‘of least concern’ by the IUCN Red List. That said, like other marine animals, they could be impacted by human activities such as habitat destruction and pollution.
Top image: Stephen Frink / Getty Images
