What Are Invasive Species?
The word “ecosystem” can refer to our entire biosphere – interconnected through atmospheric gases, ocean currents, and global weather patterns that affect vast areas, or to more specific, self-reliant systems that can be thought of as smaller ecological units. Islands are the classic example of ecosystems that have become exclusive havens for certain types of life, evolving independently with their inhabitants for thousands to millions of years. It was by observing life on islands that Charles Darwin was clued into the evolutionary process, namely the part involving “allopatric speciation through geographic isolation,” when species adapt to unique habitats and become genetically distinct from their founding populations. The implication is that these species also become fragile in that they are more susceptible to change.
Following the industrial revolution of the late 18th century, humans began to really bound about the globe, by boat, plane and car, moving persons and products from one distant place to another at scale for the first time in our planet’s history, throughout which species interchange was not so common. For billions of years, for a plant or animal to stray very far from where it first evolved quite unlikely, and global travel was reserved for birds and open ocean animals like sharks and whales – species that continue to play crucial roles in transferring bioenergy across great migratory routes. But by accepting stowaways on their own journeys, people unleashed chaos on the formerly stable global order.
For example, every island on the planet underwent drastic changes as people came ashore with goats, sheep, rats, cats, dogs, stoats and innumerable new plants, reptiles and other types of flora and fauna, some introduced purposely others by accident. Some of the more opportunistic species, such as rats, are voracious and relentless, destroying almost anything they can put in their mouth from bird eggs to whole chicks. Even vegetarian species like goats and reindeer will consume the entire flora, often until they starve themselves out. Any species that is moved from one ecosystem to another is called an “introduced species,” but the select ones that cause, or are likely to cause economic or environmental harm, or harm to human health, are known to scientists and natural resource managers as “invasives” (ISAC 2006). Damage done by invasive species such as Canada geese, cownose rays, Asian carp, pythons, Africanized bees, starlings, mountain pine beetles, and mongoose, cost the United States government over $100 billion annually. What is more, a seminal study conducted by the International Union for the Conservation of Nature (IUCN), showed that of 170 extinct species with a listed (known) cause of extinction, invasive species contributed to the demise of 91, or 53%. They were uniquely responsible for the extinction of 34. Change in species composition is normal, but not at this grossly accelerated rate.
Lion Fish – Devil in Disguise
In the midst of this blue planet’s sixth extinction crisis, precipitated by none other than Homo sapiens, there are three particularly ominous invasive species of the genus Pterois, unanimously known as lionfish, zebrafish, or devil-fire fish, that have earned a nasty reputation among coral reef conservation biologists. From their native home in the Tropical South Pacific, lionfish were brought to the Atlantic, Caribbean, and more recently to the Mediterranean Sea, and have since become severely invasive. Their Caribbean introduction occurred in the early 1980’s. This was already a tragic time for Caribbean coral reefs with an ocean warming event and mysterious plague that killed off the herbivorous Diadema sea urchin, leading to an algal take-over that caused widespread coral death.
Aquarium owners prized the lionfish for its undeniable beauty, so it was somewhat inevitable that some of these pointy pets would end up in the sea. Specific introduction events in 1980’s Florida were most probably numerous, despite unapprised claims of a single individual introduction (lionfish are incapable of parthenogenesis and therefore would require at least one male and one female to reproduce!) What no one expected, was that the fish’s wild population would explode, and in just three decades become widespread from as far North as Massachusetts all the way down to the Southern Caribbean. Based on their previous success and thermal range, lionfish now threaten to extend their range across the Gulf of Mexico and as far South as far Buenos Aires. The truth is, we knew very little about these fish until they appeared in our backyard and established themselves as kings of the reef at an unprecedented rate.
More than 68 marine species have been introduced to the Florida, Caribbean, and Gulf of Mexico area in the last century, so what makes lionfish so successful and infamously invasive? First, the lionfish, being a foreigner, is unknown to Caribbean predators, and so like a rodent on a predator free island, it counts with no natural form of population control. Even venturing predators like moray eels and reef sharks are going to find them less than appetizing, for they are also highly venomous. Thirteen double-grooved dorsal spines, two pelvic spines, and three anal spines – not to be confused with the other ~16 non-venomous “rays,” have glands capable of injecting a powerful neurotoxin. In humans it causes extreme pain, sweating, respiratory distress, and even paralysis but can’t quite kill a person outright. Like with a stingray barb wound, putting the wound in hot water to break down the protein helps reduce pain and swelling. In addition, heavy, natural body armor around the face, that can even deflect a spear shot from a Hawaiian sling, makes the lionfish a worthy opponent. Their tranquil demeanor and aposematic, or warning, coloration belays their indifference to predation. If this wasn’t enough, lionfish make bunnies look like prudent family planners. Female lionfish can pop out over two hundred million eggs per year, and they start reproducing when they are less than ten months old – a young age even for a liberally minded reef fish. Their planktonic, or free drifting larvae, based on what is known about the similar scorpion fish, might also be able to drift in ocean currents for around forty days, giving them the ability to disperse far and abroad.
All of this wouldn’t be so bad if it were not for the lionfish’s vulgar eating habits. Far from being picky eaters, they will consume over 50 species of Caribbean reef fish and prefer foraging fish – the mid-level prey that endangered and overfished top-predators are sustained by. Moreover, in their native range the lionfish have the courtesy to feed only at night, but in the West, they eat night and day, their stomachs expanding thirty times in volume to accommodate their terrific appetite. Scientists speculate that the most common cause of lionfish mortality is over-eating, upon finding abundant dead fish with clogged digestive and circulatory tracts, like obese food court fanatics in a midwestern mall.
Studying the effects of such a massive invasion requires a long-term assessment that combines a lot of different types and sources of data. Thus far, our knowledge about the real impacts of this fish lurk in dark recesses like the fish themselves, but the outlook is not good. One study in the Bahamas showed a 79% reduction in foraging fish due to lionfish presence, and economically important fish and shrimp have recently been found to be well represented in the lionfish’s wide-ranging diet. With all invasive species, early detection and rapid response are the best preventative measures, as little can be done when populations have surpassed a certain thresh-hold.
The Jamaican government, among others, has set some pointed goals in responding to the lionfish crisis. The first step is continuing scientific research through strong political support and funding. Once the science is in place, there is a potential solution that has been shown to be highly effective when it comes to more commercially sought-after species – fishing (see link below to Norman’s Cay Restaurant in NYC, a leader in this effort). This solution involves first creating a market in urban areas where lionfish can be consumed at scale, and of course training fishermen and chefs in how to safely handle the venomous fish. The Puntacana Foundation, from where I write in the Dominican Republic, has even undertaken an artisanal taxidermy program where lionfish are stuffed, painted and mounted as decorative pieces, their preserved fins used to make earrings. These kinds of local solutions bring jobs and profit to the community and can even be alternative livelihoods.
Others have attempted less successful tactics, such as training local reef sharks and moray eels to adopt a taste for lionfish by feeding them the speared catch. Bitten divers can attest, however, that this only results in the smart predators looking for more free handouts. It’s not so easy to change the natural order of predator-prey relationships that have taken millions of years to evolve. A more fruitful strategy is perhaps to destroy as many fish as possible, for example by holding lionfish spearing tournaments, or scaling the use of lionfish killing robots.
My colleague James Fifer was certified to hunt lionfish through an organization in Honduras, and taught us how to properly spear the little devils using a Hawaiian sling, a tri-pronged pole spear with a sling of rubber tubing attached to the opposite end as the barbs. The spear is loosely held with one hand, the loop of the tubing slipped between the thumb and index finger and stretched tight toward the barbs so that upon releasing your grip the spear launches forth with considerable power. It is important to use a shortened version of the spear when working around fragile coral reefs, and many lionfishers have caused more harm than good by spearing coral and surrounding reef life by accident. We practiced first by impaling plastic bottle caps on the sand, easier said than done, and then with our snorkel gear practiced in the shallows on a weighted water bottle and a free-falling onion. Everyone soon got the hang of it, and after spotting a lionfish beneath the pier, not too far from the abode of our resident nurse shark, Dr. Susanne Leib made the first successful kill! James also showed us how to use a Zookeeper, a patented, hard-plastic case with an inward-facing, stiff yet flexible funnel on one end, and a removable cap with drains on the other. A freshly skewered lionfish can simply be stuffed into it underwater without having to handle the fish at all.
More Information on lionfish