Eels are elongated fish found in diverse aquatic environments, from coastal waters to deep oceans, recognized by their snake-like bodies. Their appearance can sometimes lead to questions about their potential danger or toxicity. While certain species can pose risks to humans, the term “poisonous” needs clarification to understand their actual risks.
Understanding Eel Toxicity
The terms “poisonous” and “venomous” describe different mechanisms of toxin delivery. An animal is generally considered poisonous if its toxins are harmful when ingested, inhaled, or absorbed through skin contact. In contrast, a venomous animal actively injects toxins, typically through a bite or sting. This distinction is important when discussing eels.
Many true eels, including common edible species like conger and moray eels, possess toxic proteins known as ichthyotoxins in their blood serum. These ichthyotoxins can cause muscular cramps, including those affecting the heart, and can be harmful if raw eel blood enters the bloodstream. However, these protein-based toxins are denatured and rendered harmless by heat during the cooking process. Therefore, cooked eel is generally safe for consumption, and consuming raw eel blood is not a common practice.
Eels and Foodborne Illness
A significant foodborne illness associated with some eels is ciguatera fish poisoning, caused by the accumulation of ciguatoxins. These toxins are not produced by the eels themselves but originate from microscopic dinoflagellates found on coral reefs in tropical and subtropical waters. Smaller fish consume these dinoflagellates, and the toxins then bioaccumulate and become more concentrated as they move up the food chain to larger predatory fish, including certain moray eels.
Ciguatoxins are particularly concerning because they are heat-stable, meaning they cannot be destroyed by cooking, freezing, or salting, making contaminated eel flesh dangerous to eat regardless of preparation. Symptoms of ciguatera poisoning typically appear within minutes to 24 hours of consumption and can include gastrointestinal issues like nausea, vomiting, and diarrhea. Neurological symptoms may follow, such as tingling, numbness, muscle aches, headache, and a characteristic reversal of hot and cold sensation. While fatalities are rare, symptoms can be debilitating and may persist for weeks or even months. Moray eels, especially larger specimens or their internal organs, are known to accumulate high levels of ciguatoxins, posing a risk in affected regions.
Beyond Poison: Other Eel Concerns
Beyond chemical toxicity, eels can pose other forms of danger or concern. Many eels, particularly moray eels, possess powerful jaws and sharp, backward-pointing teeth, which can inflict painful and potentially serious bites if they feel threatened or are provoked. These bites can cause extensive bleeding, deep lacerations, and are prone to secondary infections due to bacteria present in their mouths. While eels are generally not aggressive towards humans and typically avoid contact, bites often occur when a hand is mistakenly perceived as prey or when an eel’s hiding place is disturbed.
A common misconception involves electric eels, often confused with true eels. Electric eels (Electrophorus genus) are actually a type of knifefish, more closely related to carp and catfish than to true eels. These freshwater fish from South America are renowned for their ability to generate powerful electric shocks, which they use for defense, navigation, and stunning prey. An adult electric eel can produce up to 860 volts, a shock strong enough to cause significant injury to humans, but fatalities are rare. Their electric discharge is a physical defense mechanism, distinct from chemical toxicity.