Eels are a diverse group of elongated, serpentine fish belonging to the order Anguilliformes. While most eels pose no threat to humans, a few specific marine varieties possess the size and dentition to inflict serious injury. Bites are exceedingly rare and almost always occur due to mistaken identity or provocation. The primary danger comes down to species identification, as the marine moray eel is responsible for almost all recorded bite incidents, while freshwater species are generally considered harmless.
Identifying the Eels That Bite
The marine moray eel (Family Muraenidae) is the species most commonly associated with biting incidents due to its large size and specialized dentition. Moray eels have sharp, backward-pointing teeth designed for gripping slippery prey like octopuses and fish. They also possess a second, internal set of pharyngeal jaws that shoot forward to secure prey and pull it down the throat, a unique feeding mechanism that can cause deep, complex lacerations.
Morays are generally nocturnal and hide in underwater crevices, coral reefs, or craggy rocks during the day. Most bites happen when a person inadvertently disturbs their hiding spot. Conger eels (Family Congridae) are another large marine species that can inflict a powerful bite, though they are less frequently involved in human incidents. They generally prefer to flee rather than confront a human unless they are cornered or captured.
Freshwater eels, such as the American or European eel (Family Anguillidae), are largely harmless and do not pose a biting risk to swimmers. The electric eel (\(Electrophorus\) \(electricus\)), despite its name, is not a true eel but a type of knifefish more closely related to carp and catfish. The danger from this South American species is not a bite, but rather the massive electrical discharge it can generate, sometimes up to 860 volts, which is enough to incapacitate a person.
Why Eels Bite Humans
Eel bites are almost always a result of a behavioral misunderstanding. The moray eel, which has poor eyesight and relies heavily on its sense of smell, frequently bites due to mistaken identity. When a person places a hand into a dark hole or crevice, the eel may perceive the dangling fingers as a potential prey item, such as a crab or octopus, and strike defensively.
A common scenario leading to a bite involves human-initiated feeding, where divers hand-feed eels. The eel associates the presence of a hand with food and may accidentally clamp down on the hand instead of the intended morsel in a feeding response. This behavior triggers the eel’s predatory instincts.
Bites can also occur as a form of defensive aggression when an eel is actively provoked, captured, or threatened. Fishermen handling morays caught on a line or in a net are often bitten. Pulling away once an eel has clamped down can exacerbate the injury, as the backward-curving teeth cause deeper lacerations and tissue damage.
Managing an Eel Bite Injury
An eel bite, particularly from a large moray, can cause deep, jagged lacerations and puncture wounds. The immediate injury can involve extensive bleeding, and in severe cases, result in significant tissue loss or tendon and nerve damage. If the eel is clamped down, forcefully yanking the limb away is not advised, as this can deepen and lengthen the wound.
The primary concern following a bite is the significant risk of infection, which can be more dangerous than the initial physical trauma. Eels harbor various bacteria in their mouths and on their skin, including \(Vibrio\) and \(Pseudomonas\) species, which can cause serious complications like cellulitis or septicemia. Moray eel mucus also contains toxins such as hemagglutinin, which can contribute to the pain and heavy bleeding immediately after the bite.
Immediate management involves thorough cleaning of the wound with soap and water to flush out marine bacteria and potential toxins. Even small, superficial bites require medical assessment, as a doctor will need to determine the need for a tetanus shot and prophylactic antibiotics to aggressively target the marine bacteria. Deeper wounds often require professional cleaning, stitches, and monitoring for signs of swelling or redness, which indicate a developing infection.