Lionfish are one of the most pernicious invasive species swimming in today’s oceans. And now, they’ve made it as far south as Brazil on their continuing and destructive territorial expansion.
Lionfish have been migrating south for years. They were first caught in the Gulf of Mexico, likely released from the aquarium trade, in 1985, and quickly expanded into U.S. East Coast and the Caribbean. They reached South American coastlines around 2010.
But the species stalled around Venezuela and Trinidad and Tobago. For 10 years, freshwater flowing from the Amazon River into the Atlantic and a confluence of currents acted as geographic barriers, stopping the fish from continuing south. But around 2020, at a time when few scientists were watching due to the COVID-19 pandemic, lionfish began slipping under the barrier and heading south.
Now, dozens of lionfish have been spotted along 150 miles of Brazil’s coastline, according to a new study in Frontiers in Marine Science. Between March and May of this year, when the water was clear enough to track the fish, researchers and fishers documented 72 individuals in close association. Such a high concentration suggests they have likely established new, successful populations—a dangerous and often irreversible trajectory for an invasive species.
“Since March 2022, lionfish already managed to cover 700 kilometers [435 miles] of coastline,” says Marcelo Soares, a marine ecologist and lead author of the new study. He also reported the number of individuals is now above 300. “We expect lionfish to invade the remaining 6,000 kilometers of the Brazilian coast within two years if urgent actions aren’t taken.”
For many scientists, the question wasn’t if the fish species would continue moving south, but when.
“We knew once they made it through the barrier at the Amazon, they would spread like fire,” says Osmar Luiz, an aquatic ecologist at Australia’s Charles Darwin University who was not involved in the study.
The most damaging invasive fish
Lionfish, which are native to the Indo-Pacific, are incredibly destructive. Wherever they go, they wreak havoc on the local ecosystems, eating native species and disrupting food chains. It’s earned them a reputation as one of the most damaging invasive fish. In addition to spreading south to Brazil, lionfish have also established populations in the Mediterranean, by way of the Indian Ocean and the Suez Canal. Luiz says he would not be surprised if they reach West Africa soon, “hitchhiking” on currents from the Brazilian coast.
Adding to their destructive impact, lionfish release thousands of eggs every two to four days. They have backs covered in venomous spines and are incredibly adaptable to different environments and types of food. Their millions of larvae are carried far and wide on currents, sometimes even spread by hurricanes. Worst of all, they have few natural predators in their invaded ranges, and often, the threat they pose is not fully appreciated.
“They have so many traits that make them successful,” says Nicola Smith, a marine ecologist at the University of British Columbia who was not involved in the new research. “I’m not surprised they’re booking it down the Atlantic coast and are now in Brazil.”
“The lionfish is a voracious predator,” Soares says, and a lionfish invasion can threaten vulnerable species with extinction. Unlike other hunters, who switch to plentiful prey when one species has been hunted down, lionfish will relentlessly chase down the last individuals of a prey species until they’re gone.
Because of this hunting habit, endemic species—organisms found in only one area—are particularly vulnerable to lionfish. And Brazil is full of endemic species.
Lionfish in Brazil
Soares and his colleagues documented the increase in lionfish on the Brazilian coast using accounts from researchers, fishers, and social media posts. Of the 72 individuals found during the three-month survey, over half were found near human-made structures such as artificial reefs, which locals use for fishing.
“This raises concerns over what impact lionfish will have on fisheries,” Soares says. “The Brazilian coast has considerable artisanal fishing activity, which is vital for food security in an area with substantial social inequality.”
Snapper and grouper, two economically important fish, could be driven to low numbers; in the Bahamas, for instance, lionfish so effectively killed off grouper that fishing for grouper was restricted. (Grouper numbers are finally beginning to recover.)
During the survey, lionfish were found lurking in murky, sediment-choked waters. This makes the common method of managing invasive species through spear-gun fishing—in which underwater hunters shoot and impale the fish—much more difficult.
A recent paper found that at least 29 fish species endemic to Brazilian waters are particularly vulnerable to lionfish, such as Haemulon squamipinna, a small, yellow-striped fish important to coastal subsistence fisheries. Hundreds of miles offshore, rocky archipelagos such as the Fernando de Noronha are home to numerous species with some of the smallest geographic footprints in the world—some, says Luiz, are contained in just a few square meters.
“We don’t yet know all of our marine biodiversity, especially rare and cryptic species,” Soares says. “If lionfish populate these habitats at the same densities that they have reached in the Caribbean, local population reductions are a possibility among rare and cryptic species.”
Now that lionfish have established populations in Brazilian waters, the next, inevitable step is for them to spread even farther.
“Once [lionfish are] in the establishment stage, you can fish and fish and fish as much as you want,” says Smith. “But you’re dealing with a losing situation, because they’ll just keep reproducing and replace themselves.”
The challenge of taming lionfish
For other fish species, removing individuals from an area would result in lower population densities. But not with lionfish, Smith says.
“As fast as you cull the lionfish, they’re able to recolonize,” Smith says. Because lionfish tend to move to areas with low lionfish populations, “The more lionfish you cull, the more rise up from the deep to replenish what you removed.”
Human-driven efforts to reduce lionfish populations include fishing tournaments, which can quickly remove many individuals over a large area, and specially designed lionfish traps, although about half escape, Smith says. Chefs have also pushed to turn lionfish into a popular seafood option.
But it’s not easy to turn an invasive fish topped with venomous spines into a local delicacy. People often think lionfish are not safe to eat. They’re also more time-consuming to hunt with a spear because of the dangerous spines, and their filets, while tasty, are small.
According to Smith, it is still worth trying to turn lionfish into dinner.
“I’ve eaten lots of lionfish. It’s good, it tastes like grouper,” Smith says.
While efforts to fully eliminate them may be futile, efforts to reduce their populations help limit damage to native species. Luiz says that the important next step is to track lionfish as they move and try to prevent them from establishing new populations. Monitoring offshore locations, including far-flung archipelagos, that aren’t frequented by fishers or tourists will be important.
For the native species of Brazil, this fight is a matter of survival.
“The best management we can hope for is to avoid them driving any of the native species to extinction,” Luiz says.