Lionfish invasion: The invasive fish are eating so many native species that they’re obese.

The Worst Marine Invasion Ever

The Worst Marine Invasion Ever

The state of the universe.
July 1 2013 7:00 AM

The Worst Marine Invasion Ever

I could not believe what I found inside a lionfish.

A Lionfish swims in a display tank in the aquarium on the United Arab Emirate of Sharjah on August 6, 2008.
A lionfish in an aquarium

Photo by Alexander Klein/AFP/Getty Images

"Do you know what this is?" James Morris looks at me, eyes twinkling, as he points to the guts of a dissected lionfish in his lab at the National Ocean Service’s Center for Coastal Fisheries and Habitat Research in Beaufort, N.C. I see some white chunky stuff. As a Ph.D. candidate at the Hawaii Institute of Marine Biology, I should know basic fish biology literally inside and out. When I cut open a fish, I can tell you which gross-smelling gooey thing is the liver, which is the stomach, etc. 

He's testing me, I think to myself. Morris is National Oceanic and Atmospheric Administration's pre-eminent scientist studying the invasion of lionfish into U.S. coastal waters. He’s the lionfish guy, and we met in person for the first time just a few days earlier. We're processing lionfish speared by local divers, taking basic measurements, and removing their stomachs for ongoing diet analyses. Not wanting to look bad, I rack my brain for an answer to his question. It's not gonads. Not spleen. I’m frustrated with myself, but I simply can't place the junk; I've never seen it before. Finally, I give up and admit that I'm completely clueless.

Close-up on the insides of an obese North Carolinian lionfish.
Close-up on the insides of an obese North Carolinian lionfish

Photo by Christie Wilcox

"It's interstitial fat."



"Fat," he says firmly. I look again. The white waxy substance hangs in globs from the stomach and intestines. It clings to most of the internal organs. Heck, there's got to be at least as much fat as anything else in this lionfish's gut. That's when I realize why he's pointing this out.

"Wait ... these lionfish are overweight?" I ask, incredulous.

"No, not overweight," he says. "Obese." The fish we're examining is so obese, he notes, that there are even signs of liver damage.

Obese. As if the lionfish problem in North Carolina wasn't bad enough.

Though comparing invasions is a lot like debating if hurricanes are more devastating than earthquakes, it’s pretty safe to say that lionfish in the Atlantic is the worst marine invasion to date—not just in the United States, but globally. Lionfish also win the gold medal for speed, spreading faster than any other invasive species. While there were scattered sightings from the mid-1980s, the first confirmation that lionfish were becoming established in the Atlantic Ocean occurred off of North Carolina in 2000. Since then, they have spread like locusts, eating their way throughout the Caribbean and along every coastline from North Carolina to Venezuela, including deep into the Gulf of Mexico. When lionfish arrive on a reef, they reduce native fish populations by nearly 70 percent. And it’s no wonder—the invasive populations are eight or more times as dense than those in their native range, with more than 450 lionfish per hectare reported in some places. That is a lot of lionfish.

These alien fish didn’t just come here on their own. Early guesses as to how the lionfish arrived ranged from ships’ ballast water to the coastal damage caused by Hurricane Andrew, but now scientists are fairly sure that no ships or natural disasters are to blame. Instead, it’s our fault. Pretty, frilly fins made the fish a favored pet and lured aquarists and aquarium dealers into a false sense of security. We simply didn’t see how dangerous these charismatic fish were—dangerous not for their venom, but for their beauty. We have trouble killing beautiful things, so instead we choose to release them into the wild, believing somehow that this is a better option when, in actuality, it’s the worst thing we can do. Released animals rarely survive in the harsh real world, but it’s even worse when they do. Pet releases and escapees have become problematic invaders all over the country, from the ravenous pythons in Florida to the feral cats of Hawaii. In the case of lionfish, multiple releases from different owners likely led to enough individuals to start an Atlantic breeding population. Rough genetic estimates suggest that fewer than a dozen female fish began what may go down in history as the worst marine invasion of all time.

Lots, and lots, of lionfish caught by the Discovery Diving crew on one day.
Lots and lots of lionfish caught by the Discovery Diving crew on one day

Courtesy of Discovery Diving

In North Carolina, the lionfish invasion can be seen at its worst. Offshore, where warm waters from the Gulf Stream sweep up the coast, the lionfish reign. Local densities increased 700 percent between 2004 and 2008. I got to witness the unfathomable number of lionfish firsthand when I dove with the crew of Discovery Diving, a local scuba shop, to compete in North Carolina’s inaugural lionfish derby. I’ve never seen so many lionfish in my life. I didn’t get more than 20 yards from my starting point before I saw hundreds—literally, hundreds. My spear couldn’t fly fast enough to catch them all. On the last day of the tournament, a six-diver team bagged 167 lionfish from one site in two dives, and they didn’t even make a dent in the population on that wreck site. Morris estimates that more than 1,000 lionfish are at this site. Let me tell you, this is what an invasion looks like. An ecological cascade has been set in motion by these Indo-Pacific fish, and scientists are frantically gathering data, learning as much as they can to understand the extent of the damage lionfish will inflict, and figuring out the best responses to protect these fragile marine ecosystems.