QuestionRed lionfish
Are Lionfish Venomous? Spines, Venom and Real Risk to People
Yes, lionfish are venomous. A red lionfish has 18 sharp fin spines that can inject venom into anyone who touches or steps on it, causing intense pain and swelling. The venom is used only for defense, and although stings are very painful, they are rarely life-threatening to healthy adults.
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Where is a lionfish’s venom?
The venom of the red lionfish and its relatives is stored in the spines of three sets of fins. There are 13 spines in the dorsal fin along the back, 3 in the anal fin on the underside, and 1 in each of the two pelvic fins below the chest, making 18 in total.
Each spine has a pair of grooves running along its length, filled with soft venom-producing tissue and covered by a thin skin sheath. When a spine punctures skin, the sheath is pushed back, the tissue is torn and venom flows along the grooves into the wound. The lionfish does not choose to inject venom, so every puncture can deliver some.
The long, feathery pectoral fins that make lionfish look so spectacular are not venomous, and neither are the soft rays at the back of the dorsal and anal fins.
What does lionfish venom do?
Lionfish venom is a mixture of proteins. In laboratory studies it has affected heart rate, heart muscle and blood pressure in test animals, which helps explain why a sting can cause effects beyond the wound itself.
In people, the main symptom is sudden, intense, throbbing pain at the puncture, which can spread up the hand or arm. Swelling, redness and sometimes blistering follow. More severe cases can include headache, nausea, vomiting, sweating, dizziness, numbness and difficulty breathing. A few people have serious allergic reactions.
Deaths are extremely rare, and healthy adults almost always recover fully. The risk is higher for young children, older people and anyone with heart problems or allergies. Anyone stung by a lionfish should seek emergency medical help immediately, by calling 911 in the US, 112 in the EU or 999 in the UK.
How do people get stung?
Lionfish do not chase or attack people. Almost all stings happen because a person touches the fish, usually by accident.
- Divers and snorkelers who steady themselves on a reef or reach into a crevice where a lionfish is resting.
- Aquarium keepers cleaning or rearranging tanks that hold lionfish.
- People handling caught lionfish, including those taking part in removal programs in the Atlantic, where the fish are invasive.
When threatened, a lionfish turns its spines toward the threat and may hover in place or swim slowly toward a diver with its dorsal spines pointed forward. This is a defensive display, not an attack, but it is a clear signal to back away.
Venomous or poisonous: can you eat lionfish?
The difference between the two words is how the toxin is delivered. A venomous animal injects its toxin with a spine, fang or stinger. A poisonous animal is harmful when it is eaten or touched. Lionfish are venomous, not poisonous.
Because the venom is found only in the spines, lionfish meat contains no venom. Lionfish is a mild white fish that is sold in markets and served in restaurants in Florida and around the Caribbean. In the western Atlantic, eating lionfish is actively encouraged to help control an invasive species, as described in Why are lionfish invasive?
How do lionfish compare with other venomous fish?
Lionfish belong to the scorpionfish family, which contains many venomous species. By one estimate, scorpionfishes and their relatives cause around 40,000–50,000 stings worldwide each year, second only to stingrays among venomous fish. Most of these stings are painful but not dangerous.
| Fish | Where it lives | How dangerous to people |
|---|---|---|
| Red lionfish | Indo-Pacific reefs; invasive in the western Atlantic | Very painful; rarely life-threatening |
| Devil firefish | Indian Ocean and Red Sea; invasive in the Mediterranean | Similar to the red lionfish |
| Reef stonefish | Shallow Indo-Pacific reefs and tide pools | The most venomous fish; stings can be fatal |
| Stingrays | Warm coasts worldwide, including the US and Mediterranean | Painful tail spine wounds; deaths very rare |
The stonefish is the real danger among the lionfish’s relatives. It looks like a lump of rock or coral, so people step on it, and its venom is far more potent than a lionfish’s. Stingrays cause many stings on sandy beaches, as explained in Are stingrays dangerous?, and other venomous animals are compared in the most venomous animals.
Why are lionfish so colorful?
The lionfish’s bold stripes and spread fins work as a warning. Biologists call this aposematism: bright, contrasting colors that advertise that an animal is dangerous. Predators that try to bite a lionfish once learn to avoid fish that look like it.
This is why lionfish behave so differently from most reef fish. Instead of darting away, they swim slowly in the open and rely on their spines for protection. That confidence is part of what makes them easy for divers to photograph, and also easy to touch by mistake.
How to stay safe around lionfish
Staying safe is simple: enjoy lionfish from a distance.
- Never touch, chase or try to pick up a lionfish, even a small one or one that looks dead.
- Keep hands off the reef and do not reach into holes or under ledges.
- Watch where you put your feet in shallow water on tropical reefs, where stonefish may also hide.
- Leave handling of lionfish to trained people with proper protective equipment.
If someone is stung, seek emergency medical help immediately, by calling 911 in the US, 112 in the EU or 999 in the UK.
Frequently asked questions
Can a lionfish kill you?
It is extremely unlikely. Lionfish stings cause severe pain but are rarely life-threatening to healthy adults. Young children, older people and anyone who has an allergic reaction are at greater risk, so every sting should be treated as an emergency.
How many venomous spines does a lionfish have?
A red lionfish has 18 venomous spines: 13 in the dorsal fin along its back, 3 in the anal fin and 1 in each of the two pelvic fins. The long, feathery pectoral fins are not venomous.
Are lionfish poisonous to eat?
No. Lionfish are venomous, not poisonous, and their venom is found only in the fin spines. The flesh contains no venom and is widely eaten in Florida and the Caribbean, where eating lionfish helps reduce an invasive species.
Do lionfish use venom to hunt?
No. Lionfish catch prey by cornering it with their fins and sucking it into their mouths. The venomous spines are purely defensive and are used to deter predators.
How long does a lionfish sting hurt?
The pain is usually most intense for the first few hours, while swelling and soreness can last for days. How long symptoms last depends on how deeply the spine went in and how sensitive the person is.
What is the most venomous fish?
Stonefish, relatives of the lionfish that hide on reefs in the Indian and Pacific Oceans, are generally considered the most venomous fish. Their stings are far more dangerous than lionfish stings and have caused deaths.
Sources and further reading
- Florida Museum of Natural History, Discover Fishes, "Red Lionfish"
- Animal Diversity Web (University of Michigan), "Pterois volitans"
- Encyclopaedia Britannica, "Lionfish"
Cite this page
“Are Lionfish Venomous? Spines, Venom and Real Risk to People.” Animal Atlas, https://animals.bigworldlist.com/questions/are-lionfish-venomous/.
