Lionfish are one of the most spectacular reef fish to see while diving or snorkelling. They have dark red stripes and attractive fan-like fins that splay out in all directions, says Melissa Hobson. They also happen to be one of the ocean's deadliest animals...
These gorgeous fish make quite the impression on scuba divers and potential predators but their extravagant costume is a warning signal, reminding observers to keep away from their venomous spines.
Their beauty comes with another dark side: lionfish have spread from their original home in the Indo-Pacific into tropical waters all around the world. Once there, they breed so quickly that nothing seems to be able to stop them.
Where do lionfish live?
With their striking red markings and trailing fins, these elegant predators are one of the most recognisable fish found on a coral reef. Once found in the Indo-Pacific, they have spread to tropical waters around the world. Lacking any predators in these regions, the voracious hunters have gorged themselves on many of the native fish, causing several problems for the reef ecosystem.
They are considered an invasive species in the Caribbean, western Atlantic and the Gulf of Mexico[MH1]
They are usually found in shallow coral reefs of up to 55m but recorded as deep as 91m in Florida.
What do lionfish look like?
Although many reef fish are bright and colourful, lionfish are – arguably – the most flamboyant. Their cream bodies are covered in dark red and brown bands. These striking markings warn other animals to steer well clear.
Fanning out from its body, a lionfish’s fins extend like a lion’s mane (hence the name). As well as looking fabulous, these fins protect the lionfish from potential attack by making it look more intimidating. It also has 18 venomous spines that can deliver a harmful toxin – 13 are on its dorsal fin, three on its anal fins and two on its pelvic fins (one on each side).
How big are lionfish?
They can grow up to around 38cm in length and weigh up to 1 kg
How long do lionfish live?
Lionfish can live up to 15 years
What do liuonfish eat?
They have a broad range of different prey, eating small fish, crabs, and shrimp among other animals. Able to cram large prey into their huge mouths, lionfish have been seen eating fish up to half their size.
How do they hunt?
Lionfish are usually nocturnal hunters, seeking out their prey under the cover of darkness (although some have been found with full bellies during the day).
Their venomous spines are useful as self-defence but they’re not a part of their arsenal when attacking prey. Instead, these predators stalk their prey, waiting for the perfect moment to strike, which they do with super speed.
This strategy works well for them. In one study, they were successful in gobbling down their prey in three quarters of their hunting attempts.
Scuba divers on a night dive sometimes see an opportunistic lionfish using the beam of their torch to help them hunt.
How have they become so widespread?
One area that has been particularly hard hit by the introduction of the species is the Atlantic Ocean and Caribbean, where they have no natural predators.
The first lionfish in the USA was seen in Florida in the 1980s. Over the years, they multiplied and spread. By the 2000s, they could be found off the coast of North Carolina, South Carolina and Georgia. Reports of these invasive fish began to snowball since the mid-2000s. By 2010, they were also seen in the waters around Pensacola and Apalachicola, off the Gulf of Mexico. They may have followed ocean currents to spread into these new areas.
There are several rumours about how lionfish became so widespread. They may have been introduced when people changed their minds about their aquarium pet and dumped them into the sea – just a few lionfish coming together and starting to reproduce planted the seeds to spark a full-blown invasion. Some people also wonder whether transport boats capsized during Hurricane Andrew in 1992, allowing their predatory cargo to escape into Florida’s waters.
In some countries with a lionfish problem, divers will go spearfishing for these animals and serve their meat in restaurants – once the spines have been carefully removed, lionfish are safe to eat – as a way of trying to keep the problem in check and generating income for local people.
How can they harm coral reefs?
Outbreaks become problematic when the lionfish population explodes, eating smaller fish and leaving native species without enough food. In one scientific experiment, when lionfish were introduced to an area, numbers of young native fish dropped by 79 percent. By picking off the species that eat algae, their presence can also result in algae becoming overgrown and smothering the reef. Once lionfish have taken over an area, it’s very difficult to return the ecosystem to its prior state.
What should you do if you get stung bt a lionfish?
When it comes to these stunning animals: look but do not touch. Although the stings from their venomous spines aren’t usually fatal to humans, they can cause extremely painful swelling.
If you get stung by a lionfish, clean the wound with freshwater as soon as possible and carefully remove any spines. Then, submerge the wound in water as hot as the patient can stand without being scalded (no more than 45°C) for between 30 and 90 minutes. You’ll want to get it looked at by a medical professional, too, in case you need any further treatment.
How do they breed?
Another reason lionfish have become so numerous in many locations is how quickly they breed. Females become sexually mature before they are one year old and can spawn every few days, releasing a floating jelly-like mass containing tens of thousands of eggs every time
. Even though only a small proportion of these will make it to adulthood, they are still producing huge numbers of young compared to other reef fish – female lionfish can release around two million eggs each year.
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