Eels are elongated, serpentine-shaped fish found in marine and freshwater environments worldwide, distinct from aquatic snakes. While most species are harmless, certain eels pose threats through powerful bites, unique electrical discharges, or toxicological risks associated with consumption.
Moray Eels and Biting Hazards
The danger from marine eels, particularly members of the Moray eel family (Muraenidae), stems from their formidable bite and the resulting physical trauma. Moray eels are generally non-aggressive, but they will bite defensively if threatened or if a hand is mistaken for food, especially when hiding in crevices. Their powerful bite is delivered by sharp, backward-pointing teeth designed to prevent prey from escaping, which often results in deep, jagged lacerations.
Some moray species also possess a second, pharyngeal set of jaws that project forward to secure prey. The sheer force of the jaws and the difficulty in extracting a limb can sometimes lead to the loss of a digit or a near-drowning situation if the person is underwater. The most serious complication is the high risk of secondary infection from bacteria, such as Vibrio, residing in the eel’s mouth. Prompt medical attention and antibiotics are necessary to prevent serious conditions like septicemia.
The Unique Danger of Electrical Discharge
Electric Eels are not true eels but knifefish belonging to the genus Electrophorus. These South American freshwater fish generate a powerful electrical field for navigation, hunting, and defense. A large adult can produce high-voltage discharges, sometimes exceeding 600 volts, in short, intense bursts.
The strong electric shock works by activating the motor nerves of a target, causing involuntary muscle contraction and temporary paralysis. While a single jolt is rarely fatal, the shock causes intense pain and temporary incapacitation. The main life-threatening risk to humans is secondary injury, such as drowning, because the shock can immobilize a person in the water. Multiple shocks may lead to respiratory failure or cardiac arrest, especially for those with pre-existing heart conditions.
Clarifying Eel Venom and Consumption Risks
A common misconception is that eels are venomous like snakes, but true venom delivery mechanisms are absent. However, the blood of eels, including common species like the moray and freshwater eels, contains ichthyotoxins.
Ichthyotoxins in Blood
These toxins are heat-labile, meaning they are easily destroyed by cooking, which is why eating properly prepared eel is safe. Consumption of raw or insufficiently cooked eel blood can lead to poisoning symptoms like vomiting, diarrhea, and respiratory distress.
Ciguatera Poisoning
A more significant toxicological risk is Ciguatera Poisoning, caused by the accumulation of ciguatoxins (CTXs) in the eel’s flesh. These neurotoxins are produced by microscopic algae called dinoflagellates. The toxins bioaccumulate up the food chain to large predatory marine eels, such as morays. Ciguatoxins are not destroyed by cooking, and consuming an eel with high levels of the toxin can result in severe neurological symptoms. Moray eels are considered a high-risk species for ciguatera, and the liver and viscera are particularly dangerous due to high toxin concentration.
Safe Practices When Encountering Eels
Avoiding eel-related incidents requires respecting their natural behavior and habitat.
Moray Eel Safety
Moray eel incidents can be avoided by following these practices:
- Avoid reaching into holes, crevices, or beneath rocks where moray eels hide, as defensive bites most often occur there.
- Never attempt to hand-feed any eel, as this conditions them to associate humans with food and increases the risk of an accidental or provoked bite.
- Any severe bite must be thoroughly cleaned with soap and water.
- Seek immediate medical assessment due to the high risk of bacterial infection and potential for deep tissue damage.
Electric Eel Safety
In areas where electric eels are present, such as in certain South American rivers, it is important to avoid wading in murky water where the fish may be concealed. If an electric eel is encountered, moving away slowly is the safest course of action, and one should never attempt to touch or provoke the animal. Following a shock, the person must be removed from the water to prevent drowning and monitored for signs of respiratory or cardiac issues.