Please note:
Our changing exhibit, "Amazon Voyage: Vicious Fishes and Other Riches," has closed.
Mo's Seven Perils of the Amazon
As he welcomes you to the "Amazon Voyage: Vicious Fishes and Other Riches exhibit", Captain Moacir (Mo) Fortes spins a yarn for tourists: "…there are a thousand kinds of fish we can enjoy but there are seven who can enjoy us." As you travel through the exhibit you'll meet these seven perils: Electric Eel, River Stingray, Black Caiman, Anaconda, Piranha, Piraíba and Candirú.
(artwork by Ray Troll)
Peril 1: Electric Eel
The electric eel (Electrophorus electricus) is an eel-shaped fish that can grow up to 8 feet long. It's justifiably famous —or notorious— for the intense bursts of high voltage it uses to stun prey. These discharges, which can exceed several hundred volts in larger individuals, can also be used as a defense. The shock is strong enough to stun and injure large animals, including humans.
The remarkable shock of the electric eel is created by specialized organs that have evolved from muscle tissue. These organs, which run along most of the animal's length, consists of a series of current-producing cells called electocytes that function like a long series of tiny batteries. The bigger the fish, the stronger the shock.
The electric eel is not a true eel. It's actually a species of knifefishes (Gymnotiformes), which are relatives of catfishes. Also known as electric fish, knifefishes use weak electrical charges to navigate murky waters, find prey and communicate with one another. The electric eel is the only knifefish that uses its electric charge to actually capture prey (fish and small mammals). There are about 85 species of knifefishes, all of which are found in the warm inland waters of tropical South America and southern Central America. [web links]
(artwork by Ray Troll)
Peril 2: Freshwater Stingray
Freshwater Stingrays are the most feared fishes in the Amazon. That fear is justified. They are not aggressive, but you are more likely to run afoul of these distant relatives of the shark than you are of the most fearsome predator.
Ironically, a stingray "attack" is actually an act of self-defense. If it's threatened, it will lash back with a poisonous spine from its tail. This spine, which is barbed and fed with venom, can be driven deep into the offender's flesh. Thousands of river stingray incidents are reported each year in South America, many of which result in serious injury or even death.
Bad encounters with these dangerous animals are most likely to occur during fishing. Freshwater stingrays are frequently —but unintentionally— caught in fish nets. You may not want them, but they have to be removed from the wriggling mass of fishes that you do want.
Stingray trouble can also happen if you're swimming or walking in shallow water, especially during the dry season. They will bury themselves in sand or mud and are very difficult to spot. It's way too easy to step on one.
There are several species of freshwater stingrays in the Amazon, all of which belong to an exclusively freshwater family, the Potamotrygonidae. The ocellate (Potamotrygon motoro), porcupine (Potamotrygon hystrix), and raspy (Potamotrygon scobina) river stingrays, and the discus ray (Paratrygon aiereba) are the most familiar of these rays. Some are strikingly colored or patterned. Widths range from 10 inches to 3.5 feet.
River stingrays are not fished for food, but they are important to the aquarium trade. They can readily be bred in captivity, but there is virtually no commercial breeding and most of these fish are caught in the wild. Freshwater stingrays, like their cousins the sharks, have extremely low reproduction rates. Moreover, several species are geographically restricted to specific tributaries of the Amazon. This raises concern that some of these species may vulnerable to extinction. The the size of this threat remains unknown. [web links]
(artwork by Ray Troll)
Peril 3: Black Caiman
The Black Caiman (Melanosuchus niger) is the largest member of the alligator family in the Amazon system. It can exceed 12 feet in length and is among the river's top predators. Adults usually feed on fish, turtles, capybaras and birds, but they sometimes capture more formidable prey such as tapirs, jaguars, anacondas and —reportedly— an occasional human. The young feed on invertebrates.
Although it's large and formidable, the black caiman is easily hunted by humans. In fact, overhunting has reduced its populations by perhaps 99% during the last 100 years. Hunting is now illegal and some populations are recovering. However, illegal hunting is a serious problem. [web links]
(artwork by Ray Troll)
Peril 4: Anaconda
There are four species of anaconda in South America, but the most famous —and largest— species is the green anaconda (Eunectes murinus). This species can grow up to 30 feet long and weigh over 500 pounds. It is among the longest of reptiles and unquestionably the heaviest.
Anacondas are related to boa constrictors and, like the boas, they can suffocate their prey by coiling and squeezing. More often, anacondas lurk in the water, seize the prey with powerful jaws and drags the victims underwater to drown. Anacondas usually feed on capybaras, tapirs, peccaries, turtles, fish, birds and an assortment of other small to medium-size mammals. On rare occasion, they may attack jaguars and humans. [web links]
(artwork by Ray Troll)
Peril 5: Piranha
Without question, piranhas are the most famous —or infamous— fishes of the Amazon. Armed with an interlocking array of sharp teeth and powerful jaws, piranhas are capable of inflicting serious bites. However, the piranha's reputation as voracious killer —and as a dire threat to humans foolish enough to enter the water— is greatly exaggerated.
There are more than 30 recognized species of piranha and there are several more still to be discovered or scientifically described. Most of these can be found in the Amazon system, and of these, only a few species pose a danger to humans or their domesticated animals. Most other species are docile and many feed on plants or small prey.
Most frequently, the hazard occurs during fishing. Piranhas are prized both as food and for the aquarium trade, but getting them off a hook or out of a net can be tricky. They bite.
The feeding frenzies for which piranhas are notorious actually do occur, even if the accounts of them are sensationalized. This behavior is most likely to occur during the dry season when the piranhas are concentrated and food is scarce. The presence of blood or the thrashing of a struggling animal can trigger a feeding frenzy so experienced locals and travelers take precautions. For example, they don't clean fish in the water.
The red-bellied piranha (Pygocentrus nattererii) is the most familiar of the many species of piranha. It's the one with the nastiest reputation. It's also popular among some aquarium enthusiasts. [web links]
(artwork by Ray Troll)
Peril 6: Piraíba
The Piraíba (Brachyplatystoma filamentosum) is probably the largest catfish in the Amazon and among the biggest in the world. Size estimates vary, but the most reliable record is of a fish almost 12 feet long and weighing 440 pounds. Such a giant is now exceedingly rare, but catches of fishes 6 feet long are not exceptional.
A large fish like the piraíba can be intimidating and there are occasional reports of it attacking humans, but the piraíba, also known as laulau or kumakuma, is not considered dangerous. On the other hand, it's is prized for both commercial and sport fishing so people are clearly a danger to it. In fact, the piraíba is threatened with overfishing.
Piraíbas live in the deeper waters of large rivers and are known to migrate considerable distances up and down the larger river. They typically feed on fish, but are also known to feed on small mammals. At least one individual was found to have fed on monkeys. [web links]
(artwork by Ray Troll)
Peril 7: Candirú
Sometimes called the "devil in the water", the candirú is among the most feared fish in the Amazon. It's a parasitic catfish that normally lodges itself into the gills of other fishes to feed on their blood, but it can also attack humans. These attacks appear to be exceedingly rare, but given the psychological impact of the way in which they attack, their reputation is understandable.
The candirú is notorious for entering human urethras, presumably because they mistake a stream of urine for the flow of water over the gills of its normal victims. Once lodged in the genital-urinary tract, it's extremely difficult to remove. Surgery is one option. There is also a folk remedies that use plant extracts to kill and dissolve the fish. Unfortunately, the victim could succumb to serious infection before the parasite can be removed. To add to the hazard —and notoriety— the candirú has a small, slender and translucent body. It's almost impossible to detect these fishes in the water.
The fishes known as the candirú actually represent several related species. Vandella cirrhosa, which can grow up to seven inches in length, is the most familiar and perhaps the most common of these. It's also the one for which an actual attack has been documented. Many of the others are smaller than Vandella cirrhosa and are also parasitic on other fishes. They all belong to the Trichomycteridae, a family commonly known as pencil or parasitic catfishes. [web links]
Web Links for the Seven Perils
- Electric Eel
- Animal Diversity Web: Electric eel (accessed April 25, 2007)
- Fishbase.org: Electrophorus electricus (accessed April 24, 2007)
- Tree of Life: Gymnotiformes (accessed April 25, 2007)
- Wikipedia.oprg: Electric eel (accessed April 24, 2007)
- Freshwater Stingrays
- Fishbase: Potamotrygonidae - River stingrays (accessed April 25, 2007)
- Wikepedia: Potamotrygon (accessed April 25, 2007)
- Black Caiman
- Crocodilian Species List: Black Caiman (accessed April 24, 2007)
- Wikipedia.org: Black Caiman (accessed April 24, 2007)
- Piranha
- Animal Diversity Web: Pygocentrus nattereri (accessed April 25, 2007)
- The Nature Conservency: Red-bellied piranha (accessed April 26, 2007)
- Shedd Aquarium: Red-bellied piranha (accessed April 26, 2007)
- Smithsonian National Zoo: Amazonia Species Facts: Piranha (accessed April 26, 2007)
- Wikipedia.org: Piranha (accessed April 25, 2007)
- Piraíba
- Fishebase.org: Brachyplatystoma filamentosum (accessed April 24, 2007)
- Wikipedia.org: Brachyplatystoma (accessed April 24, 2007)
- Candirú
- Fishbase.org: Vandellia cirrhosa (accessed April 24, 2007)
- Fishbase.org: Trichomycteridae (accessed May 3, 2007)
- Wikipedia.org: Candiru (accessed April 24, 2007)