Ricardo Araújo was getting ready for work in late 2020 when his phone lit up with a dreadful message: For the first time, someone had spotted a lionfish, an invasive predator, lurking near the waters of Brazil’s Fernando de Noronha Marine National Park, a biodiversity haven and iconic scuba diving destination off the country’s northeastern coast. The fish was killed the next morning, but nobody dared celebrate. “We knew we were in for a war,” says Araújo, the park’s research manager.

Lionfish are native to the Indian and Pacific oceans, but were introduced to the Atlantic decades ago. First spotted off Florida in the 1980s, they later spread across the Caribbean, reshuffling coral reefs and other ecosystems by feasting on fish unfamiliar with the voracious predator. Ocean currents that flow north—including the South Equatorial Current—and the freshwater plume created by the Amazon River slowed the fish’s spread, but scientists predicted it was just a matter of time before it moved into Brazilian waters.

Still, they’ve been alarmed by just how quickly the invasion has progressed (see map, below). As of March, lionfish have been spotted along about half of Brazil’s coastline, from the northern state of Amapá to Pernambuco, just south of the nation’s eastern tip.

Lionfish on the march

D. An-Pham/Science

Now, researchers say the invasion is entering a worrying new phase. The fish have reached areas where the Brazil current flows south, speeding the spread of drifting larvae and putting vast new swaths of ecologically rich waters at risk. “I’ll be very surprised if they don’t reach [Brazil’s] southern states by the end of this year,” says Luiz Rocha, a Brazilian ichthyologist at the California Academy of Sciences.

So far, no country has been able to eradicate invasive lionfish, which grow fast and breed prolifically. Off Brazil, those characteristics have resulted in “an uncontrolled population explosion,” says Marcelo Soares, a marine scientist at the Federal University of Ceará.

That initial explosion was largely invisible to Brazilian researchers, Soares says, because the COVID-19 pandemic and budget cuts disrupted research activities. “While lionfish were out there proliferating, we were stuck in lockdown, with no money for fieldwork.” Despite the difficulties, a network of researchers tracking the invasion has validated nearly 360 lionfish sightings since 2020.

Scientists are particularly concerned about the potential impact on native fish found around Brazil’s oceanic islands, including Fernando de Noronha, an archipelago located 350 kilometers offshore. These islands host dozens of endemic reef fish species that tend to be small in size and hang out in limited territories—“exactly the kind of prey that lionfish love,” says Hudson Pinheiro, a marine biologist at the University of São Paulo. “The chances of lionfish having a negative impact on these species is quite high.” The worst case scenario, he says, is that some go extinct.

So far, researchers have documented 170 lionfish around Fernando de Noronha, mostly in shallower reefs. But many more are likely living and breeding in deeper seas, they say. ICMBio, the federal agency that manages the park, is hoping to enlist visitors and others in efforts to keep lionfish in check. Dive operators, for example, are now authorized to kill lionfish they find. “We know it’s impossible to eradicate it, but it’s possible to control it. That’s what we are aiming for,” says marine biologist Clara Buck, who helps run the program.

“You have to act early,” says Carlos Eduardo Ferreira, a reef ecologist at Fluminense Federal University. “The faster you move in, the more effective you can be.”

Despite such efforts, researchers forecast that lionfish will settle into the food chain and become a permanent part of Brazil’s marine fauna, sharing an ecological niche with other predators, such as groupers and snappers, whose populations have been sharply depleted by overfishing. “It will be a common fish here,” Ferreira predicts, “just like in the Caribbean.”

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