We tend not to worry when dipping our toes into fresh water. There could be a slippery rock or two to negotiate, but any fish we encounter will be placid and calm, more scared of us than we are of them. There are toothy terrors in the vastness of the sea, but we have nothing to fear in the calmer currents of our rivers and lakes. Do we?
- "Capable of striking fear into the heart of divers everywhere, it's as dangerous as it is beautiful..." 10 deadliest, most dangerous fish on the planet
- "If some stop swimming they will suffocate..." Did you know fish can do maths, walk, fly AND pee? 15 fish facts that leave you scratching your head
In fact, there are plenty of snapping jaws and knife-like teeth to be found in freshwater, where even the most innocuous looking fish might give us a nip.
Here are 10 freshwater species that might bite back…
10 most aggressive freshwater fish
Northern pike (Esox lucius)
The pike, alongside its larger North American cousin the muskellunge (Esox masquinongy), is probably the source of more fishy fables than any other freshwater fish of the Northern Hemisphere.
Although most can be discounted, there are substantiated stories of people being badly bitten by a fish that can grow to 1.5 metres and is sometimes known as a ‘freshwater shark’.
The teeth are razor-sharp, as many anglers will attest, and pike may react instinctively to a trailing hand or limb, especially in coloured water. Unprovoked attacks on people might be brief and impulsive, but the resulting lacerations may well require medical treatment.
Red-bellied piranha (Pygocentrus nattereri)
The black piranha (Serrasalmus rhombeus) may have a stronger bite, but Pygocentrus nattereri is probably the primary source of piranha-induced panic. Representations in film, television and many a tall tale may have distorted the threat of a piranha attack, but the narrative is not without substance.
Red-bellied piranha average around 35cm in length and live in large, tight shoals throughout South America. Although this social behaviour is primarily for defence, it also ensures serious competition when food becomes available. And when every shoal member wields a mouthful of razor-sharp teeth, a feeding frenzy can be dramatic and destructive. Human fatalities may be rare, but verified incidents have occurred.
Wels catfish (Silurus glanis)
A true freshwater giant, the wels is native to eastern Europe and parts of Eurasia, and is sometimes said to resemble an enormous, whiskered slug. It can grow to more than 3 metres in length and weigh more than 150 kg, with reports of fish far bigger.
They have huge, cavernous mouths, armed with rasping pads rather than teeth, although that doesn’t diminish their threat. Wels are happy to scavenge or hunt and will tackle anything that they can fit in their mouths. A spate of attacks on people in Bavaria in 2025 prompted police action and the culling of a suspected catfish culprit.
Red-Bellied Pacu (Piaractus brachypomus)
A fish that warrants inclusion purely due to the extraordinary claims made about it. The similarity of the red-bellied pacu to a red-bellied piranha is unsurprising given they are both members of the family Serrasalmidae, but their diets are significantly different.
The pacu mainly feeds upon nuts, seeds and berries, although it will adapt its diet if such foods are scarce. Growing to 25 kg in weight, the pacu is much larger than the piranha and has flatter, human-like teeth which can deliver a nasty bite.
However, the belief that they target men’s testicles given the opportunity, seems, for want of a better word, nuts.
Goliath tigerfish (Hydrocynus goliath)
In terms of weaponry, the teeth of the goliath tigerfish are surely the most extraordinary of all the 18,000 species of freshwater fish in the world. Known as mbenga – ‘dangerous fish’ – in the Congo region of Africa where it is found, the tigerfish is so-named due to the stripes along its body rather than the enormous teeth that line its mouth.
And those teeth are extraordinary. An adult fish has around 32, each measuring up to 8cm long which is comparable to those of a great white shark. Though rare, there are tales of tigerfish attacking and even killing people.
Trahira (Hoplias malabaricus)
Another predatory freshwater fish from South America, the trahira, or guabine as it is also known, rarely exceeds 60cm in length but has a fearsome reputation.
They have cylindrical bodies and spend daylight lying still in weed, waiting for darkness when they ambush prey such as crayfish, shrimp and other fish. The dagger-like teeth create deep puncture wounds, often injuring or incapacitating prey in a series of attacks rather than a singular grab, and bites on humans can cause serious bleeding.
Aquarists who keep trahira speak of their skittishness and have described fish leaping out of tanks to literally bite the hand that feeds them.
Giant snakehead (Channa Micropeltes)
With a reinforced cranium and powerful jaws, this is not a fish to underestimate, especially considering it can reach 1.5 metres in length and weigh 30kg.
Native to Malay, Southeast Asia and Indonesia, the giant snakehead has a suprabranchial chamber behind the gills that enables it to breathe air and survive for long periods out of water. This quality makes them easy to keep, and their popularity as pets has led to illegal releases and an invasive presence in North America, Taiwan and Thailand.
When threatened, the snakehead will charge, either head-butting or biting the aggressor, with reports of people having suffered serious injuries as a result.
African cichlid (Neolamprologus ocellatus)
You don’t have to be large to pack a punch and this little cichlid certainly proves that point. Found in Lake Tanganyika in Africa, this is a shell-dwelling fish that only reaches around 5cm in length.
Its gold and yellow colouration, with iridescent rays on the fins and tail, have led to the popularity of Neolamprologus ocellatus in the aquarium trade, where it is commonly known as an African cichlid, and where its aggressive reputation is founded.
The bites are more like pinches, although they can draw blood, and they will readily attack bare skin given the opportunity.
Bluegill (Lepomis macrochirus)
Native to North America, the bluegill is another feisty little fish that is unafraid to punch above its weight. They rarely exceed 30cm in length and are familiar in shallow areas of lakes and slow-moving rivers, where they can be abundant.
When breeding, the male bluegills create small spawning beds and become increasingly territorial. This period may coincide with attacks on swimmers or bathers, and although the sucker-like bites are not too painful, they are quite common. What is curious is an apparent correlation between bluegill bites and the presence of minor skin lesions or moles.
Goonch catfish (Bagarius yarrelli)
In the shadow of the Himalayas swims a fish that seems to have developed a taste for human flesh.
The goonch catfish grows to more than 150 kg in weight and has a huge mouth lined with small, sharp, slanted teeth.
In the early 21st century, a series of fatal attacks on the Kāli River drew international interest. Adventurer Jeremy Wade visited the region and speculated that the Hindu tradition of Asthi Visarjan, where the dead are burned on riverside pyres with their remains turned into water, had provided an unlikely food source for the goonch, which subsequently struggled to discern the dead from the living.
Be careful where you paddle….
Top image credit: abadonian/Getty Images
