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.

(Continued from Page 1)

Despite the destruction, it’s hard not to be impressed by these colorful aliens. Part of me holds lionfish in the highest regard, with a sort of evolutionary awe. They’re an incredible fish. Given complete creative freedom, I cannot imagine a way to design a marine species more suited to dominance. Sure, they might not be at the top of the food chain like sharks or killer whales, but what they lack in size they make up for in adaptability and reproductive output. The key to their Darwinian success is that they grow fast, mature early, and breed year-round. A single female can release upward of 2 million eggs annually that become larvae capable of floating along currents for more than a month, dispersing for hundreds to thousands of miles. They’ll eat whatever they can get their mouths around, which happens to be any fish or invertebrate just a hair smaller than they are, and they can grow to more than 18 inches long. That means young fish and crustaceans of any species that live where lionfish do are potential targets. And, to top it all off, they are armed with a formidable set of long, sharp venomous spines capable of inducing incapacitating pain. Not surprisingly, nothing seems inclined to eat them. They’re known for their cavalier attitude toward divers, ignoring our presence or possessing the gall to approach us head on, even in the face of a spear. Their cocky resolve is admirable. It’s abundantly clear that these fish fear nothing, not a hungry grouper, not the largest of reef sharks, not even the most effective predators on the planet—us.

Christie Wilcox cutting open a lionfish to remove its stomach.
The author cuts open a lionfish to remove its stomach.

Photo by NOAA intern Dave Matthews

Of course, we are perhaps the only animal that lionfish should be fearful of, the only species potentially capable of controlling lionfish populations. Scientists, managers, fishermen, and locals from Venezuela to North Carolina are rallying behind “Eat Lionfish” campaigns. Lionfish tournaments have become annual events in some of the most heavily hit areas of the Caribbean and Atlantic. The Reef Environmental Education Foundation released a lionfish cookbook in 2010 to spur culinary interest and inform fishermen and chefs how to clean and prepare this new delicacy. But even with a serious fishery throughout the invasive range, we will likely never evict lionfish from their new homes. Studies have suggested that we’d need to fish more than a quarter of the mature lionfish every month to stunt population growth, let alone reverse it. Our best hope is to keep local populations low enough to protect key commercial and ecological species, a mission that is proving to be harder and harder as we realize just how much lionfish eat.

We’ve always known that lionfish are formidable predators. As slow-moving fish, they have to be pretty effective hunters to get away with such flamboyant looks. After all, it’s not like their prey won’t see them coming. They practically advertise their presence, waving around their frilly, striped fins with a level of arrogance usually reserved for apex predators. In their native range, young fish run from the sight. But in the Atlantic, native fish have never seen such a bizarre-looking predator. They don’t realize that this colorful display is a warning, not only of their potent venom but also of a nearly insatiable appetite. They don’t flee, and they get eaten. And in North Carolina, the lionfish are eating so well they’ve become fat. No, not fat. Obese.

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As James Morris and I measured and sliced 247 fish last month, he explained that we have to monitor their diets to understand how lionfish may impact native fish.

So far, more than 70 different species have been found in the stomachs of invasive lionfish, but detailed data on what they regularly eat in many different areas and throughout the year hasn’t been collected—yet. That’s one of the questions Morris is in the process of answering, and that’s what I helped him with while I was in North Carolina collecting samples for my own research on lionfish venom.

The coast of North Carolina is renowned for its seafood. Cold waters from the north and the warm Gulf Stream converge at Cape Hatteras, creating some of the richest fishing grounds on the Eastern Seaboard. More than 60 million pounds of fish and shellfish are pulled out of its waters every year, worth upward of $1 billion to commercial fishermen. Lionfish are eating a lot of something, and if these gluttons are eating key commercial species, there could be a negative ripple effect on the local economy.

Vermilion snapper pulled from a lionfish's stomach.
Vermilion snapper pulled from a lionfish's stomach

Courtesy of NOAA

One species Morris is particularly concerned about is the vermilion snapper. One of the smallest of the species often labeled as red snapper, vermilion snapper are the most frequently caught snapper along the southeastern United States. Because of their popularity, vermilion snapper populations are closely monitored, and their harvest has been managed in a variety of ways, including limited entry systems, annual quotas, size limits, trip limits, and seasonal closures. So far, government assessments say that the populations are not overfished, but fisheries-watch organizations such as the Monterey Bay Aquarium aren’t convinced. What we know for certain is that vermilion snapper are among the most heavily managed fish in North Carolina, and all of our efforts will be for naught if the lionfish are getting to them first.

So far, it’s not looking good.

I personally pulled vermilion snapper out of lionfish guts last month, along with tomtates and various other reef fish. It’s estimated that lionfish in the Bahamas eat upward of 1,000 pounds of prey per acre per year. Given that lionfish feed largely on small fishes, this equates to hundreds of thousands of individual fish consumed per year by lionfish per acre. But all the interstitial fat I saw suggests that the North Carolinian fish aren’t just eating until they’re full; they’re overindulging on the rich diversity of seafood that North Carolina has to offer. Though lionfish can go weeks between meals, when they don’t have to, they won’t. Scientists have observed lionfish eating at a rate of one to two fish per minute, and their stomachs can expand 30 times their size to accommodate lots of food. To become obese, fish eat upward of 7.5 times their normal dietary intake, which means the abundant North Carolina lionfish could be eating as much as 7,000 pounds of prime North Carolina seafood per acre every year—seafood that we’d much prefer ended up on our plates instead.

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