The colorful and charismatic lionfish are proliferating on the coral reefs of Bermuda, Florida, the Bahamas, and the Caribbean. Although non-native to the Atlantic, it’s becoming hard to miss them in many areas.  That’s good, you might be thinking.  Divers spend a lot of money to travel to coral reefs in the Indo-Pacific where these fishes are native and provide visual delights for underwater photographers.  Whip out those cameras — an added attraction has shown up to add zing to the diving experience on Atlantic coral reefs, you say.

Unfortunately, like most invasive species scenarios – recall the ecological and economic mess created by the infamous zebra mussel - the lionfish introduction and rapid geographic spread is proving far from ecologically harmless to Atlantic coral reefs.  In fact, scientists are quite concerned that lionfish may be completely reinventing the western north Atlantic coral reef ecosystem – permanently!

What are these lionfish doing in the Atlantic in the first place and what’s going on?  Here’s some background: Lionfish belong to the scorpionfish family (which includes the venomous scorpionfish and stonefish).  Even if you don’t dive you’ve likely seen them as they are very popular in the aquarium trade.

Two species are now known to occur in the western Atlantic: the red lionfish (Pterois volitans) and the devil firefish (Pterois miles), with the former occurring in much greater numbers.  The two species are similar looking and it took DNA evidence to confirm that there are indeed two species that have invaded the Atlantic.  They’ve been around for a while, with the first observation in the Atlantic occurring near Fort Lauderdale, Florida in 1985!  Considered a rarity at first, lionfish populations have exploded over the past 25 years and especially over the past decade, spreading far north and south.  They now range at least from Bermuda to Venezuela.  It’s really worth tracking their remarkable and disconcertingly fast spread at: http://nas.er.usgs.gov/taxgroup/fish/Lionfishanimation.gif.  If you dive in the Bahamas you’ll know that they are over running the reefs.

So what’s the worry?

Invasive Lionfish in the Bahamas. Photo: Courtesy of B. Watts

It’s an ecological nightmare.  In spite of a mountain of unknowns, researchers agree on a few key points: lionfish are voracious predators and prolific breeders.  They devour the young of other reef fish species, including several commercially important species, and even crustaceans such as newborn lobsters.

In addition to their own direct impact on reducing other fish populations by predation, lionfish are outcompeting native fishes for food.  Not a good scene for native fishes.  Lionfish can suck up about 80% of all small or immature fish in a section of reef in only five weeks.  Their predation on young herbivorous fish also means reduced control of algae, which can overgrow and kill coral.

How bad is it? There are enormous concerns that lionfish will completely change and possibly destroy Atlantic coral reefs by overrunning them and shrinking their native biodiversity, and that the ongoing damage is severe and possibly irreparable.  So far, there is no known quick-fix, and the problem is escalating exponentially.

Lionfish are the lions of the Atlantic reefs; they sit enthroned near the top of the food web where almost nothing eats them.  Scientists don’t fully understand why lionfish have no natural predators in the Atlantic. Observed cases of lionfish being eaten by other fish are so few that they can be counted on one hand. Would-be predators seem to shy away from the lionfish’s poisonous appearance – even when lionfish are in their larval stage. Possibly for this reason, invasive lionfish have encountered practically no natural opposition since their introduction, when the first individuals were probably dumped into the Atlantic as unwanted aquarium pets. Without effective population control, the lionfish – also called the red firefish – spread like, well, wildfire.

It’s easy to see why. Lionfish reach sexual maturity in only about one year. For the rest of their adult lives, female lionfish lay batches of 25,000-30,000 eggs almost twice a week (about every four days). Do the math, and you will quickly discover what this means. Each year, there are easily over two million eggs for each female lionfish. These eggs quickly develop into living vacuum cleaners. Each lionfish eats fish up to two-thirds of its own size, and lionfish stomachs stretch up to thirty times their normal size when feeding.

Ironically, studies are showing that lionfish are now present in higher densities in some Atlantic regions than they are in their native Indo-pacific habitats! Maybe the Atlantic environment is just making female and male lionfish more romantic. Or maybe it’s a lack of predator thing. Or maybe their Atlantic prey have fewer defenses?

So, what can be done? Many scientists think that the rapid pace of lionfish population growth and geographic spread means that nothing can completely stop the destruction by this invading beauty. But perhaps the momentum can be slowed if control measures are quickly and widely implemented.

Lionfish meat is excellent in taste and texture, and lionfish dishes have been added to the menus of many exclusive restaurants. In fact, the US federal government’s chief fisheries management agency, the National Oceanic and Atmospheric Administration (NOAA) has developed an “Eat Lionfish” campaign to increase the public’s awareness of the issue and create a consumer market for this tasty invader. Several coastal communities host fishing events called lionfish derbies where prizes go to the anglers who catch the most, and an enormous celebratory barbecue comes at the end of each derby. Many recreational anglers would attest that, after a long day of fishing, grilled lionfish with a cold beer is a hard treat to beat!

These triumphs, however, are small ones. Fishing alone cannot solve the lionfish problem. It will also take both education and dedication. As an increasingly prominent marine “poster child” against non-native species release, the lionfish example further proves that release can have unpredictable, unprecedented, and literally dire consequences. Please never release your exotic pets. A simple desire to let one animal “have a better life” in the wild can so easily create an irreparable ecosystem and economic mess.

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