Electric Eels And Pollution: What's The Impact?

Electric eels are native to the waters of northern South America, including Brazil, the Guianas, Suriname, Venezuela, Colombia, Ecuador and Peru. They are a type of knifefish, more closely related to catfish and carp than to other eel families. They are capable of generating up to 800 volts of electricity, which they use for defence, hunting, communication and navigation.

Electric eels are listed as a species of least concern by the International Union for Conservation of Nature's Red List, as of 2009. However, there is evidence that they are affected by noise and chemical pollution.

Noise pollution has been shown to make critically endangered European eels more likely to be eaten by a predator. In a study, eels were half as likely to respond to a predator's ambush when surrounded by ship noise, and those that did react did so at rates about 25% slower than usual.

Chemical pollution has also been shown to have a detrimental effect on the health of eels. They are particularly prone to accumulating and biomagnifying lipophilic and persistent organic pollutants and other chemicals. This is due to their status as benthic and opportunistic predators, and the fact that they accumulate extraordinarily high amounts of body fat during their continental lives.

Research has shown that chemical pollution impairs the health of eels, affecting their ability to swim, accumulate energy reserves, develop healthy oocytes, and reproduce.

Electric eels are more closely related to catfish than to other eel families

Electric eels are not actually true eels and are more closely related to catfish. They are a genus, Electrophorus, of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volts.

Despite their name, electric eels are not closely related to true eels (Anguilliformes) but are members of the electroreceptive knifefish order, Gymnotiformes. This order is more closely related to catfish. In 2019, electric eels were split into three species: Electrophorus electricus, Electrophorus voltai, and Electrophorus varii.

Electric eels have long, stout bodies and can reach 2 metres (6 feet 7 inches) in length, and 20 kilograms (44 pounds) in weight. They have smooth, thick, brown-to-black skin with a yellow or red underbelly and no scales. They are nocturnal, obligate air-breathing animals, with poor vision complemented by electrolocation. They mainly eat fish and grow for as long as they live, adding more vertebrae to their spinal column.

The name Electrophorus comes from the Greek words ήλεκτρον ('amber, a substance able to hold static electricity') and φέρω ('I carry'), giving the meaning 'electricity bearer'. Electric eels were first described by Carl Linnaeus in 1766, who noted that the fish is from the rivers of Surinam and can cause painful shocks. In 1864, Theodore Gill moved the electric eel to its own genus, Electrophorus.

Electric eels can generate up to 800 volts of electricity

Electric eels, or Electrophorus, are a genus of neotropical freshwater fish from South America. They are known for their ability to stun their prey by generating electricity, delivering shocks of up to 860 volts.

Electric eels are not true eels but are members of the electroreceptive knifefish order, Gymnotiformes, and are more closely related to catfish. They are nocturnal, air-breathing animals with poor vision, and they mainly eat fish. Electric eels can grow to be quite large, with males larger than females, and they can live for over 20 years.

The electric eel's ability to generate electricity is due to the presence of three pairs of electric organs: the main organ, Hunter's organ, and Sachs' organ. These organs are made up of electrocytes, modified from muscle cells, and allow the eel to generate two types of electric organ discharges: low voltage and high voltage. The low-voltage discharge is used for navigation and locating prey, while the high-voltage discharge is used for attacking and paralysing prey.

The maximum discharge from the main organ of an electric eel can reach at least 600 volts, making them the most powerful of all electric fishes. The high voltage discharge is produced extremely rapidly, at a rate of up to 500 Hertz, with each shock lasting only about two milliseconds.

In addition to stunning prey, electric eels can also use their electricity for defence. They have been observed to leap out of the water to deliver electric shocks to potential threats, such as large mammals or humans. The shocks from leaping electric eels are powerful enough to drive away animals as large as horses.

Electric eels are native to northern South America

The two rivers these fish inhabit are subject to a natural fluctuation of water driven by precipitation patterns, which results in two distinct seasons: wet and dry. The two seasons bring about drastic changes in available habitat for electric eels. During the rainy season, the rivers swell, re-connecting lakes and ponds as the forests flood. Juvenile electric eels disperse and expand into new territories. As water recedes in the dry season, large groups of fish become isolated in the pools and smaller streams that remain.

The water in these areas is poorly oxygenated, but electric eels are specially adapted to thrive in this environment. They are obligate air-breathers, which means they surface for air periodically. Their mouths are heavily vascularized with folds that increase the surface area, allowing them to breathe air, rather than trying to meet their respiration needs through gills in warm, anoxic waters.

The average lifespan of electric eels in the wild is still unknown. In human care, males typically live 10 to 15 years, and females generally live 12 to 22 years.

Electric eels are listed as a species of least concern by the International Union for Conservation of Nature's Red List, as of 2009.

Electric eels are obligate air-breathers

Electric eels have three specialised electric organs – the main electrical organ, the Hunter's organ, and the Sachs' organ – that make up about 80% of their body. These organs create strong and weak electric charges, which are used for defence, hunting, communication, and navigation.

The strong electric charges can be energetically exhausting for the eel, so they are reserved for defence. The weaker electric discharges are used for communication and hunting. Electric eels can detect these signals and interpret information about other individuals in the water, including their sex and sexual receptivity.

Electric eels are nocturnal, with poor vision compensated by electrolocation. They are also capable of hearing.

Electric eels can jump out of the water to deliver electric shocks

Electric eels are known for their ability to generate electricity and stun their prey by delivering shocks of up to 860 volts. In recent years, scientists have discovered that electric eels can also leap out of the water to attack predators or defend themselves. This behaviour was first documented by the naturalist Alexander von Humboldt in 1800 and later confirmed by Kenneth Catania, a professor of biological sciences at Vanderbilt University, in 2016.

Catania's experiments revealed that electric eels leap out of the water and press their chins against a target to deliver a high-voltage shock. By doing so, the eels minimize the loss of current to the water, increasing the strength of the shock. This strategy is particularly effective against terrestrial or semi-aquatic predators and may be more common during the Amazonian dry season when eels are found in small pools and are at greater risk of predation.

In one of Catania's experiments, he approached an eel with his hand in a container with a metal strip on it. The eel leaped out of the water, pressed its chin against the metal, and delivered an electric shock. Catania described this as a "pretty shocking experience" even though he was wearing protective gloves.

The ability of electric eels to leap out of the water and deliver electric shocks adds a new dimension to their defensive capabilities and further highlights the sophistication and nuance of their behaviour. This discovery also has implications for understanding the evolution of electric eels and their place in the animal kingdom as it demonstrates a unique defence mechanism.

While the impact of pollution on electric eels specifically is not well-documented, noise pollution has been shown to negatively affect European eels, a critically endangered species. Man-made noises can cause stress, decreased coordination, and impaired evasion abilities in these eels, making them more vulnerable to predators. It is possible that other forms of pollution could also impact electric eels, but further research is needed to confirm this.

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