Saving the Ocean- ‘Scourge of the Lionfish’: The story behind the showPosted: August 19, 2013
Here’s a brief extract from the research conducted for Saving the Ocean’s show ‘Scourge of the Lionfish‘. The show is part of the ten-part PBS series hosted by author and marine biologist, Carl Safina, and is dedicated to exploring the extent of the problem along with identifying and crediting those who are pitching in to curb it.
Click here to watch Saving the Ocean on PBS.
In the last couple of years, the Atlantic Ocean and its neighboring Caribbean Sea has come under siege from a population of brightly colored invasive fish, the Lionfish. They are terrific breeders, have a voracious appetite and are armored with spiny, venomous dorsal fins– all high-ranking markers on the ultimate-predator checklist. Native to the Indo-Pacific, Lionfish are the first highly predatory fish to become an invasive in Caribbean coral reefs, an extremely delicate and highly threatened ocean habitat.
The United States Department of Agriculture defines ‘invasive species’ as any plant, animal or other living organism that is alien to an ecosystem and whose introduction is likely to cause economic harm, environmental damage or harm to human health. Deliberate or otherwise, human actions are the primary reasons for invasive species introduction.
It was no different for lionfish. Lionfish didn’t swim their way across the oceans- people brought them here and released them into Atlantic waters. Their flaming colors and unique spiny appearance made them a favorite among aquarium fishes which was the main reason for their trade. Scientists speculate that their introduction was a result of hurricanes and aquarium releases. Today, their invasive range extends from as far north as Rhode Island, all the way south to Columbia, and what’s worse is that it’s expected to expand further south until the frigid waters of the Southern Ocean dissuade them. Lionfish are densely populated in the Caribbean Sea due to their affinity to coral reef structures. Their range is not only wide it’s also deep. Submarines have reported spotting these fish at depths of 1000 ft.
Native to the Indo-Pacific, lionfish were first spotted off the coast of South Florida in 1985, and were sporadically seen for 15 years following that. But experts say that the real invasion began at about the turn of the 21st century. By 2005, they were spotted in the Bahamas and in the Caribbean, around Florida Keys and in the Gulf of Mexico. Since then their numbers have grown exponentially and research shows that their growth has led to a sharp decline among native fishes. Lionfish feed on all kinds of small reef fish and juveniles of larger species like groupers. They also don’t spare tiny coral-cleansing fish like parrotfish that feed off algae growing on corals. Other favorites include tiny parasite fish that clean larger species. They can eat upto 5-6 times of their body weight in a year. “In the Bahamas alone, there has been a reduction in populations of 60 species of prey fish in the last two years,” says Stephanie Greene, biologist from Simon Frasier University. Mark Hixon, zoologist at Oregon State University, backs up those figures with his own studies on lionfish’s insatiable feeding behavior. “We have witnessed colorful cardinalfish, parrotfish, damselfish all going down the lionfish’s gullet. One consumed 20 small fish in 30 minutes.” In a controlled experiment conducted in 2005, Hixon recorded that a single lionfish can reduce the number of other fishes by 79 percent in as few as five weeks. Underwater footage from the Caribbean show coral reefs poxed with lionfish, bearing testimony to his claim. With a strong density of 400 individuals per hectare in the Caribbean (ten times as much as in their native ecosystems), lionfish pose a catastrophic threat to reef ecology and commercial fishing.
Lionfish are accoutered with unique anatomical and behavioral characteristics that make them the ultimate predator in their alien surroundings. Their modified dorsal fin forms a series of venomous spines that can ward off even large predators like sharks and groupers. James Morris, an ecologist at NOAA, discovered that even when starved, sharks reject a lionfish meal. When force-fed, sharks have shown visible signs of discomfort sometimes even resulting in regurgitation of the venomous fish. It’s assumed that this defense mechanism has given lionfish the needed confidence to drift languidly in their Caribbean surroundings. Their unusual movement pattern along with their spiny, colorful appearance might be the reasons why native species don’t recognize lionfish as predators, prey, or even just fish. Hixon’s team discovered yet another interesting feeding behavior unique to lionfish– they blow jets of water in the face of their prey. As fish naturally swim upstream, a confused prey fish will dart towards the source of the jet stream presenting itself as an easy meal. Lionfish also use their dorsal fins to herd prey fish into corners before swallowing them whole.
In addition to their entitled appetite, Lionfish are endowed with an indefatigable reproductive rate. They reproduce every 3-4 days and females can produce a couple of million eggs every year. Juveniles reach sexual maturity when they are less than a year old, a stark contrast to other predators their size. Females release eggs in a gelatinous mass that is speculated to contain a chemical deterrent to ward off predators. Even if the speculation proves wrong, no Caribbean fish has thus far recognized this floating gelatinous mass as food. This could be because no native fish releases eggs in such a manner. Lionfish larvae are equipped with venomous spines and adults do not feed on their young. They live long, some even longer than 30 years. All these traits cumulatively allow them to multiply at an alarming rate. Morris says that it’s impossible to remove lionfish completely from the Caribbean. “ We’ll have to remove a quarter of the population every month for a whole year in order to bring it down to a point where the population is no longer increasing,” said Morris. “It would take armies to remove them.”
Lionfish are much less abundant and threatening in their native ecosystems of the Indo-Pacific. Hixon’s team is studying lionfish and their native environment to compare it to lionfish in the Atlantic and Caribbean. Their studies are still nascent but the team assumes that it could be combinations of natural diseases, parasites and predators that are absent in the Atlantic but keep lionfish in control in the native surroundings. The largest lionfish in the Pacific, thus far is 38 cm while in the Atlantic, they have found individuals that are 45 cm long.
With all odds in favor of the invasion, scientists have concluded that the only immediate way to control lionfish is manual removal. This task is made complicated by the fact that lionfish dwell close to reefs, ruling out trawling as an option. They don’t bite so it’s impossible to fish them using hook and line. This leaves just one option that is both successful and dangerous- spear fishing. Lionfish are naturally inclined to be calm and unafraid of predators, which make them easy targets for divers. The incentive for this dangerous task is a tasty lionfish meal. The fish, once de-spined is noted to be very mildly flavored, easy to cook with a variety of marinades and is delicious on its own as a sashimi. Non-profits like REEF host diving derbies and cook-outs all over Florida Keys and the Caribbean. They routinely hold training workshops for fishermen to teach them careful spearing, without destroying corals, and lessons on handling and cleaning the venomous fish. Lionfish are often caught in lobster traps too, lured in by their affinity to structure. REEF is encouraging lobstermen in the Florida Keys to supply their lionfish to local restaurants and is hence, turning their bycatch into profit.
Restaurants all over the Caribbean and in major cities in the US now feature lionfish on their menus. Traditional Fisheries, the only wholesale distributor of lionfish in the US, sources its fish from the mesoamerican reefs off Puerto Morelos in Mexico. David Johnson, president of the company, is married to a Mexican woman whose five brothers are all spear-fishermen. With the help of his brothers-in-law and local fishing coops, Johnson has established a flourishing lionfish fishing and packaging industry in Puerto Morelos, supplying fish to casinos and restaurants in Vegas, NYC and other big cities. Johnson is currently experimenting with alternative methods to harvest the invasive by using vacuum pumps that can hopefully reduce the amount of time spent on each dive.
Although successful, these curative methods are a mere drop in the ocean. Lionfish are found at great depths of 1000 ft whereas scuba divers can safely dive down to only 300 ft. In order to catch several lionfish at a time, divers have to stay underwater for a dangerously long time. If not done skillfully, spearing could also damage delicate coral structures and organisms. This, however, is not discouraging researchers and conservationists who are working hard to create reef pockets that are completely devoid of lionfish. Their hope is that by creating a safe haven for native species, the ocean will have a chance to recover and defend itself from the invasion.