Fish are one of the most diverse species we know of, and you’d find them living in some of the most diverse places on Earth – from tropical rainforests to mountain rivers to densely-populated urban centers.
While most fish are harmless underwater creatures that want to do nothing with you, there are some species that can at best completely ruin your day, and at worst kill you within seconds. The deadliest fish in the world also happen to be some of the deadliest creatures on the planet, armed with a surprisingly wide variety of ways they can cause harm to anyone unlucky enough to cross paths with them.
10. Moray Eel
Moray eels are a family of eels found around the world, characterized by their frightening jaws and aggressive behaviour. While it’s uncommon for people to get bitten in the wild, it can happen if you’re swimming in one of its habitats. There have also been cases of morays biting the hands of people trying to feed them at home.
A bite from some of the bigger species can cause serious laceration or even loss of a finger if not treated in time. Bite wounds from some moray species can be unusually painful and bleed more heavily than other fish species, thanks to the variety of poisons found in their bodies, including ones that can destroy red blood cells and delay clotting.
Thankfully, their preferred habitats – mostly brackish water bodies – are hardly ideal swimming spots, making encounters with humans relatively rare.
9. Titan Triggerfish
Titan triggerfish is the largest of triggerfish species found in tropical ocean waters around the world. Its habitat stretches across the Indo-Pacific region, including Fiji, Thailand, the coral reefs of Australia, Maldives, Philippines and the Indonesian islands. Generally speaking, Titan triggerfish aren’t very aggressive, and it’s not uncommon for divers to encounter them in one of their habitats. During reproduction season, however, they may as well be one of the most dangerous and aggressive fish species we know of.
Titans have attacked divers in all sorts of ways during nesting season, including biting off their fins and attacking their equipment. Actual bites have been rare, though not as rare as we’d like. Some divers have even been bitten through the suits, and according to them, it was still quite painful. Sometimes, they may not bite at all and just aggressively swim towards you to escort you out of their zone, though we’d suggest not counting on that and just avoiding diving wherever these things are found.
Fortunately, despite their strong bite-strength and surprisingly aggressive behavior, Titan triggerfish have no venom.
Almost all lionfish species could be easily recognized by their distinct, vibrant look. Native to the Indo-Pacific region, all lionfish species are colorful and great to look at. If you’re diving in one of their habitats and happen to see one, you may even want to swim closer to get a closer look. Get too close, though, and their bite can deliver one of the most potent venoms found in the oceans.
Lionfish venom can cause a range of serious symptoms like delirium, convulsions, dizziness, heart attacks, loss of consciousness and high fever, and even death among people allergic to it. While their bites have been rarely fatal, they make up for it by being unusually aggressive towards divers and scaring the hell out of them.
They’re also one of the most invasive species in the world. Because of this invasive nature, their habitat now includes the waters of the Gulf of Mexico, Atlantic and Caribbean.
The Candiru is barely an inch in length, though that’s the only part of its description that’s not horrifying. It’s a parasitic fish from the catfish family, and mostly feeds on the blood of other marine and land animals for survival. It can usually be found inside the gill cavities of various other fish, though if you’re not careful, they can easily enter the human body, too.
There have been cases of swimmers getting invaded by this species through their urethra, where it lodges itself using its spines and starts feeding. The candiru can stay inside a host for a long time, making removing it even more and more complicated with time. Without medical attention, a candiru infection could lead to severe inflammation, hemorrhage, and even death.
6. Electric Eel
Technically speaking, electric eels aren’t eels, as they’re closer to catfish and carp on the family tree than eels. Found in the Amazon and Orinoco river regions, these creatures share one of the most unique and distinct evolutionary traits found in nature; the ability to produce electricity. Only a few other species – like the electric rays and electric catfish – can do this, though there haven’t been many cases of them attacking humans.
Electric eels, though, have regularly proven to be one of the most dangerous fish species to encounter in the wild. They can generate up to 600 volts of electricity to ward off predators, or just if they’re pissed off enough. While there haven’t been many deaths due to electric eel shock attacks, that may be because of a lack of records than anything else. People have definitely died due to respiratory or heart failure caused by the shock, or drowned in shallow water after being electrocuted.
Stingrays only got popular when one of them killed Steve Irwin – also known as the Crocodile Hunter – though they’ve always been one of the deadliest creatures you can encounter underwater. They’re quite ancient, too, as the stingray family diverged from sharks some time around 200 million years ago.
Unlike many other species on this list, stingray venom hasn’t been properly studied. There are over 200 ray species found in habitats around the world, ranging from rivers, swamps, lakes and oceans, all packing venom that can cause a range of complications if not treated in time, including death.
Thankfully, stingray venom hasn’t caused many casualties in the past, and the species usually keeps to itself. However, there have been many cases of unsuspecting hikers and swimmers stepping on one and getting bitten on the leg or foot. While it usually turns out ok, a bite from one of the more venomous species – like the one that got Irwin – can easily turn fatal without medical care.
4. Goliath Tigerfish
Tigerfish is a family of fish found across Africa, and could be recognized by its humongous size and scary-looking jaw. Some species – like the Goliath Tiger, mainly found in the Congo river and nearby regions – can grow up to 110 pounds and 1.8 meters in length, and that’s only the largest one recorded.
While most tiger fish species are harmless to humans, the Goliath is the only one that regularly attacks swimmers and is generally aggressive to anyone found in its territory. Imagine it as a nightmarishly-larger version of the piranha, as it attacks in a similar way, too. While they’re not poisonous, if you just take a look at them, you’d see that they don’t need to be. They can – and often do – easily kill much larger prey, and you’d often find them attacking in groups. They’re aggressively-territorial, too, and the best way to avoid facing one in the wild is simply not swimming in the same water bodies as them.
3. Sea Wasps
Jellyfish species are known for their unique appearance and surprisingly-painful venom, though most people assume that it can’t be fatal. While it’s true that most jellyfish species can’t kill you, there are a few that definitely can, the deadliest one being the box jellyfish family.
Some species – like the Australian box jellyfish, also known as sea wasps – are also some of the most venomous creatures found in the oceans. They sting using tiny, poison-filled darts on their tentacles called nematocysts. It’s so strong that it can cause a heart attack, full-body paralysis, loss of consciousness and even death, all within a few minutes of getting bitten.
On top of all that, it’s nearly impossible to spot them in the ocean, as they’re usually almost-completely transparent. At least 63 people have died from sea wasp stings in the past 80 years, and that’s just in Australia.
2. Stone Fish
Stone Fish are named for their appearance, as it’s not difficult to mistake them for a random stone on the seabed while swimming. Anyone who makes this mistake and happens to step on one, though, would most likely end up in the hospital, and that’s if they’re lucky. While there’s debate around whether they’re the most poisonous fish in the sea, as ‘poisonous’ can mean a lot of things, stone fish are definitely somewhere around the top.
Usually found in habitats at the bottom of the sea in the Indo-Pacific region, stone fish species can be really difficult to spot due to their excellent camouflage. They’re not particularly aggressive to large species they can’t possibly eat – like humans – though a bite is a real possibility if you step on them.
While there haven’t been many deaths due to stone fish bites – thanks to the widespread availability of an effective antidote near its natural habitats – they can potentially do a lot of damage if left untreated. Stone fish venom can cause paralysis, tissue necrosis, heart failure, and even death within hours of being bitten.
1. Puffer Fish
Another contender for the ‘most poisonous’ title in the fish world, puffer fish are named after their tendency to puff up into a ball to ward off predators. However, that’s only for the times their venom doesn’t work. Almost all pufferfish species are armed with generous doses of a type of venom called tetrodotoxin, which is about 1,200 stronger than cyanide and could kill within a few hours. There’s no known antidote, either, making them particularly dangerous to swimmers in remote areas.
Despite its lethality, one puffer fish species – fugu – has gained a reputation in Japan as a delicacy. Its meat – at least the edible part – is one of the most expensive food items you could find across the country, and only experienced, licensed chefs are allowed to prepare it. That’s despite the fact that by some estimates, eating fugu still kills about one person per year in Japan.