Most electric fish

The electric eel, or poraquê (Electrophorus) – native to river systems in the tropics of South America and Central America – was long considered to be a single species. However, a study published in Nature Communications on 10 September 2019 revealed that there are, in fact, at least three species: Electrophorus electricus (the original binomial used since Linnaeus’s description in 1766); E. voltai; and E. varii. All electric eels can grow to 1.8 metres (5 feet 10 inches) long – though larger specimens are occasionally reported. These fish are capable of producing electricity thanks to three dedicated paired organs – the main, Hunter’s and Sach’s organs – distributed across their elongated bodies. Until now, the highest discharge reported for an electric eel is between 550 and 650 volts. However, an examination of the electric organ discharges (EODs) in this study highlighted a significant variance in output among the three species: E. electricus produced 480 volts, E. varii up to 572 volts and E. voltai 860 volts – meaning the latter takes the record for bioelectricity production in the animal kingdom.

The distribution of the three different species has been divided into three general regions, with some cross-over: E. electricus is restricted to the Guiana Shield (the Guianas and Suriname); E. voltai to the Brazilian Shield of northern Brazil edging into the Guianas; while E. varii’s range, in contrast, is far greater, covering the entire lowland intercratonic Amazonian basin from Ecuador and Peru in the west to Brazil and French Guiana in the east.

The specimen of E. voltai that produced 860 volts was collected and recorded by William Crampton in the Lago Amorim on the Rio Tapajós in Brazil, while filming an episode of Monster Fish with Zeb Hogan for National Geographic in January 2014. The fish measured 1.219 metres (4 feet) long.

Electric eels are not true eels, but giant members of the knifefish family Gymnotidae. They belong to the order Gymnotiformes – a group of freshwater Neotropical fish that use electric fields for a range of functions.

Electric eels primarily use high-voltage shocks comprising volleys of EODs from the main organ and anterior parts of the Hunter’s organ to stun prey, such as small fish and crustaceans, and also for defence when attacked by predators such as caimans. However, they also use intermittent lower voltage pulses (about 10 volts) generated by the Sach’s organ and posterior part of the Hunter’s organ for electrolocation in the often-murky rivers and lakes where they live.

While the shock of a poraquê is certainly enough to stun a human, there are no documented fatalities caused by this fish. Indeed, inhabitants of the Amazonia region consider it more of a curiosity than a threat.

Photo credit: Erin Buxton