“Vampire fish” is a nickname shared by several fish species, but it most commonly refers to the payara (Hydrolycus scomberoides), a fanged predator found in South American rivers. With lower jaw fangs that can reach 3 inches long and a diet that includes piranhas, the payara earned the name honestly. A few other species also go by the label, each with its own blood-related claim to the vampire title.
The Payara: Amazon’s Fanged Predator
The payara is the fish most people mean when they say “vampire fish.” It belongs to the family Cynodontidae and goes by several other names: saber tooth barracuda, vampire tetra, and saber tusk barracuda. It lives in the Amazon and Orinoco river basins, thriving in both the sediment-rich whitewater rivers that flow from the Andes and the darker, low-nutrient blackwater rivers draining the Guayana Shield in southern Venezuela and Brazil.
What makes the payara immediately recognizable is the pair of elongated fangs on its lower jaw. These can grow up to about 3 inches long, which is remarkable given the fish’s overall size. The fangs are so large that the payara’s skull has evolved specialized holes in the upper jaw to house them when the mouth closes. Without those slots, the fish wouldn’t be able to shut its mouth at all.
Payara are powerful, muscular fish. The world record payara, caught at Uraima Falls in Venezuela in 1996, weighed 39 pounds 4 ounces. The longest on record measured 98 centimeters (just over 3 feet) and was caught in Brazil’s Xingu River in 2016. They’re built like torpedoes, with streamlined bodies designed for speed in fast-moving water, particularly around rapids and waterfalls.
How the Payara Hunts
Unlike many river predators that hide and wait for prey to come close, the payara is an active pursuit hunter. It uses its speed and power to chase down other fish in open water, then impales them on those long fangs before swallowing them. Its primary prey is piranhas, which makes the payara one of the few fish that regularly hunts the Amazon’s most famous predator. It also feeds on smaller characins, the broad family of freshwater fish that includes piranhas, tetras, and many other South American species.
This role as a top predator makes the payara ecologically important. Removing too many from a river system can throw off the balance of species below them in the food chain, allowing piranha and other mid-level predator populations to grow unchecked.
The Candiru: A Parasitic Vampire
The candiru is a small, translucent catfish in the family Trichomycteridae, and it earns the “vampire” label in a completely different way. Rather than hunting with fangs, the candiru feeds on blood. Species in the genus Vandellia are obligate blood feeders, meaning blood is their only food source. They range from about 2 to 20 centimeters long and have very elongated, nearly transparent bodies.
A candiru finds a host fish, then uses the spines on its gill covers and large amounts of mucus to slide into the host’s gill openings. Once inside, it makes an incision in the blood vessels of the gills with those opercular spines. It doesn’t actively suck blood. Instead, it simply positions itself against the wound while the host’s own blood pressure pushes blood out, feeding passively as the host bleeds.
The candiru is perhaps best known for the persistent claim that it can swim into the human urethra, supposedly attracted by urine in the water. This story has circulated for centuries, but there is no robust evidence that it actually happens. Scientific reviews of the claim have found that the accounts are plagued by imprecision, secondhand reports, misconceptions, and folk tales. There is also no solid evidence that candiru are attracted to ammonia or blood dissolved in water. The story makes for a dramatic travel warning, but it shouldn’t be taken as established fact.
The Sea Lamprey: Saltwater Bloodsucker
Sea lampreys are not technically fish in the modern sense (they’re jawless vertebrates that diverged from other fish hundreds of millions of years ago), but they’re commonly grouped with fish and frequently called vampire fish. During their parasitic adult phase, lampreys attach to host fish using a sucker-like mouth lined with rows of small, sharp teeth. They rasp through the host’s skin and feed on blood, sometimes for days or weeks.
What makes the lamprey’s feeding so effective is its saliva. The secretion from its mouth glands, sometimes called lamphredin, contains a cocktail of compounds that prevent the host’s blood from clotting. Multiple proteins work together to break down fibrinogen, the key clotting molecule in blood, ensuring the wound stays open and flowing. Other compounds in the secretion destroy cells at the wound site, making it easier for the lamprey to access blood vessels. The host fish essentially can’t stop the bleeding as long as the lamprey remains attached.
Sea lampreys are considered a serious invasive pest in the Great Lakes region of North America, where they devastated native fish populations after gaining access through shipping canals in the early 20th century.
Dracula Fish: A Tiny Oddity
One lesser-known species that carries the vampire name is Danionella dracula, a miniature fish from Myanmar described by scientists in 2009. It’s a cyprinid, which means it’s related to carp and zebrafish, a group that lost its teeth roughly 50 million years ago. What makes D. dracula so unusual is that males have re-evolved fang-like structures on their jaws. These aren’t true teeth but bony projections called odontoid processes that poke through the skin and look strikingly like canine fangs.
The fish itself is tiny and highly simplified. Compared with its close relative the zebrafish, D. dracula is missing 44 bones or parts of bones, making it one of the most developmentally reduced vertebrates known. Its body retains many larval-like features, as if development stopped partway through. Yet against that stripped-down background, males developed these elaborate fang structures, which are thought to play a role in competition between males rather than feeding. Only males have the fangs, making them one of the more dramatic examples of sexual differences in fish.
Keeping Payara in Aquariums
The payara is sold in the aquarium trade, typically marketed as vampire fish or saber tooth barracuda. It’s a challenging species to keep. These are large, fast, aggressive predators that need enormous tanks with strong water flow to mimic their natural rapids habitat. They do not do well in standard home aquariums and are generally suited only for experienced keepers with tanks of several hundred gallons or more. They also have a reputation for being sensitive to water quality and prone to stress in captivity, which can shorten their lifespan considerably compared to wild fish.