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The Lure of the Lionfish

A highly invasive scourge threatening the natural balance of a reef’s ecosystem or the ever adapting king of the reef?

Both are applicable to the Volitans lionfish, a member of the Scorpaenidae family originating from the Indo-Pacific but rapidly making themselves at home along the Atlantic coastline. Their introduction, although unconfirmed, is likely to stem from the aquarium trade and the accidental or purposeful release of unwanted individuals onto local reefs. Here they have quickly made a home and a name for themselves and in less than a decade their numbers have exploded. Populations that emanated from the Floridian reefs have now spread as far north as Rhode Island and south to Belize, with this rapid rise to ascendency showing no signs of slowing.

The Indo-Pacific lionfish is the umbrella name for two similar species from the Pterois genus, the Volitans lionfish Pterois volitans and the Common lionfish Pterois miles and it is believed to be a combination of the two at the heart of this conservational conundrum. Released into a warm coral reef environment with an abundance of unwitting prey and no natural predators, it’s hardly surprising that they have flourished.

These voracious hunters possess cavernous mouths capable of hoovering up anything unfortunate enough to fit within.  The volume of food they consume not only impacts upon the prey species themselves, but serves to out-compete local predators such as grouper or snapper, which carry great economic importance. Studies assessing Caribbean reef fish populations have found that local prey species such as Damselfish fail to recognise the Volitans lionfish as a threat, making them easy pickings. In heavily afflicted areas, the reduction in herbivorous fish as a consequence of lionfish predation can lead to algal blooms smothering corals and reef deterioration.

Dressed for the occasion

Head away from the reefs of the wild and into the home environment and perceptions change. They go from an unwanted pest to a stunning centrepiece, capturing the imagination and the hearts of many an aquarist. There is no doubting their eye-catching appeal. The vivid splash of red, white and black vertical bands is a far cry from the cryptic brown colouration of their scorpionfish and stonefish cousins. This willingness to be noticed and admired is an unusual tactic for an ambush predator, but there is good reasoning behind it.

Against the backdrop of a well-lit aquarium, a Volitans lionfish cuts a prominent and imposing figure. Their aposematic colouration boldly announces their venomous capabilities to the world and their spiny, elongated fin rays and flayed pectoral fins flare out at the first sign of a threat, adding further bulk and size. Potential predatory tank mates would be wise to think twice before tackling one. In the daytime, it’s fair to say the lionfish’s finery is predominantly for defence.  However, many lionfish species are crepuscular, feeding at dusk and dawn and it’s when the lights go down that the true cryptic nature of their colouration takes effect. Those conspicuous red orange, black and white stripes start to merge against a murky backdrop of reef and rock. This works to break up the lionfish’s body shape as it lurks in the shadows with its fins retracted, camouflaged from possible prey.

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Handle with care

The venomous cocktail of acetylcholine and neurotoxin that lionfish possess isn’t for exclusive use on aquatic predators and they will think nothing of administering a painful dose of venom into human body parts that get too close.  Lionfish differ from poisonous species such as pufferfish or boxfish as they are able to inject their venom, rather than relying on their victim to ingest or absorb it. At the base of the spines on the dorsal, anal and pelvic fins lie venom sacs, each covered with a loose sheath. At the point of delivery, the sheath is pushed back and the toxin is released through the spine and into the unfortunate target and the pain commences.

The good news for aquarists is that lionfish possess the weakest sting relative to any other member of the Scorpaenidae family, but any sting should still be treated with the utmost caution. Symptoms tend to include intense pain and swelling around the puncture wound, although in extreme and severe cases, stings can induce anaphylactic shock, nausea, breathing difficulties and localised paralysis. The venom is comprised of proteins that break down with heat, so treatment should consist of immersion in hot water for prolonged periods to allow for the denaturation of proteins. Most accidents in the aquarium occur during routine tank maintenance, or netting, where a hand brushes the spines. This can be avoided by wearing protective gloves, always knowing the location of your lionfish in the tank and using nets with a soft-weave to prevent spine entanglement.

Housing

Despite being predominantly ambush hunters, Volitans lionfish are active swimmers constantly in search of food. There is nothing quite like a Volitans with its fin rays extended, gliding effortlessly around its domain and a suitable set-up should reflect this need for adequate swimming space. They can grow quickly, with a newly purchased 2” individual reaching 8-10” in under a year with appropriate feeding, so tank size is important. A minimum 120gal tank is required to house an adult, with numerous rocky overhangs and caves to hide in, especially while acclimating to their new surroundings, as well as open space to stretch their fins. To enable swimming, tanks should be wider rather than taller and if the intention is to house a Volitans with other suitable fish, then a larger tank volume will be required.

Adult Volitans lionfish can exceed 15” and any other fish or invertebrate species small enough to fit inside their mouth invariably will end up as dinner. With stomachs that can expand to 30 times their normal size, these ravenous hunters will make short work of anything that moves, ruling out crustaceans and smaller fish 6” and under. While smaller species like the Spotfin lionfish Pterois antennata are intolerant of conspecifics and will fight relentlessly, the larger Volitans lionfish is less territorial and can be housed with others. Depending on the size of the tank, other suitable tank mates include species such as small moray eels, planktonic feeding triggerfish and large tangs. It is not recommended to keep more aggressive species such as pufferfish, large angelfish and other types of triggerfish as they may nip fins, or harass the Volitans.

All Lionfish are considered to be safe to house with corals, although being heavy polluters, it is this conveyor belt of waste production rather than possible predation that may preclude housing them with more sensitive coral types. The Volitans is the hardiest lionfish species to keep and can be very forgiving of fluctuating parameters and water chemistry spikes. In the past, they were often used during the tank cycling process and recent research has shown they can withstand drops in salinity down to 1.006sg, the lower end of the brackish scale. This isn’t an excuse for neglection though, with an ideal pH between 8.1-8.4, ammonia and nitrites at 0 and a constant salinity level between 1.021-1.025sg required. Lionfish are covered in a thin membranous cuticle, which they shed to remove settling parasites. During periods of reduced water quality, lionfish will shed their cuticle more regularly, with large and frequent water-changes required to counteract this.

The trickiest part of owning a lionfish can be weaning them off live foods, but Volitans lionfish are usually no trouble. Ghost shrimp enriched with marine flake make a great starter diet and the addition of frozen squid, silversides or fish chunks will often engage the lionfish in feeding immediately. If an individual does require more encouragement, wiggling food on a clear rod to give the impression it is alive should elicit a feeding response. Once weaned, lionfish will recognise their owners, often spitting water at them with surprising accuracy whilst begging greedily for food. A varied diet is important but overfeeding should be avoided, with feeding 2-3 times a week deemed to be sufficient.

Breeding

One of the keys to their successful invasion of Atlantic reefs is that lionfish can reach sexual maturity within two years and are capable of spawning every 55 days, all year round. At dusk, a male will perform a courtship dance and the pair will spawn at the ocean’s surface, where anywhere between 2,000 and 15,000 eggs may be released and fertilised. This surface spawning allows for the dispersal of their larvae and explains their rapid encroachment of territories along the Atlantic coastline. However, the pelagic stage of a larval lionfish’s early life is nigh on impossible to replicate within the home aquarium and as of yet, no breeding success has been reported with any species. Sexing a Volitans is out of the question as males and females are indistinguishable apart from just prior to spawning, when the females will turn a ghostly white and males will darken in colour.

Which species?

There can sometimes be a tendency among retailers to label all large lionfish species as Pterois volitans, so it is always worth visually checking when purchasing one. Volitans lionfish have 11 dorsal fins spines and 7 anal fin spines while the Common lionfish Pterois miles have 10 dorsal and 6 anal spines. The Russels lionfish Pterois russelii ares also sometime mistaken for a Volitans but are smaller and lack the spots on their tail and caudal fin.

Like all aquatics purchases, thorough research and careful stocking should be undertaken, but with their dog-like personality and owner recognition, a Volitans lionfish could make the perfect centre-piece addition to a large marine tank.

 

 

About Chris Sergeant

I currently work in the Conservation Biology field, having previously worked within both public and private aquatics facilities. I hold degrees in Marine Biology and Coastal and Marine Resource Management and have spent numerous hours diving and snorkelling across the world for both work and pleasure. I also keep a variety of tropical and marine species.

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