They weren’t entirely wrong. The paiche is carnivorous—although it eats other fishes, not humans. And it did enter Bolivia from Peru, where it had been added to the Convention on International Trade in Endangered Species index in 1975 as a species prone to extinction if trade was not closely controlled. A few years later a flood washed juveniles out of a Peruvian fish farm near the border into Bolivia’s watershed. By the time Bolivian fishermen noticed the strange creature, it was already established in the oxbow lakes and seasonal lagoons that dot the forest.

In the past decade paiche meat has also become more popular among city dwellers. Conservation-minded chefs in the cities promote paiche as a sustainable choice, which is true at face value: The fish is a nuisance, and other edible river fishes are disappearing. The idea is to control or maybe even eradicate the fish by deliberately overfishing it, but Salazar, who profits handsomely from the paiche’s lean, white meat, says that would be impossible. “To eradicate the paiche,” he says, “would be to pull a star from the sky.”

Bolivia is now faced with a controversy that, for the past decade, has been a central debate in the young field of invasion ecology here in U.S.: Could human hunger help control the spread of invasive species, or will the rules of capitalism, combined with our unquenchable thirst for more, only make matters worse?

Eat them to death

An invasive is any species introduced by human intervention that has caused economic or ecological damage by growing superabundant in a nonnative habitat. Invasives can be fish, bivalves, mammals or plants. They can be as sinister as kudzu (“the plant that ate the South”) or innocuous as dandelions. They can be as delicious as wild boar; as unappetizing as the parasitic sea lamprey sucking blood from native fishes in the Great Lakes (they’re a delicacy in England); or entirely inedible, like the tiny zebra mussels clogging pipes and choking native shellfish throughout the upper Midwest.

Invasive species have followed us around the globe for as long as we have been mobile. They’ve hitched on the hulls of transoceanic ships, and we’ve carried them home with us deliberately, introducing them for food, farming and recreation. Invaders are now the second-most important cause of global biodiversity loss after habitat destruction, and the more we move about, the more they spread. Conservative estimates have invasives costing the U.S. tens of billions of dollars annually.

Among the first scientists to promote gastronomy as a tool to combat invasion was Joe Roman, a conservation ecologist at the University of Vermont. His 2004 article for Audubon, entitled “Eat the Invaders,” articulated a simple argument: If we can hunt native species to extinction, as we have for eons, why not deploy our insatiable appetites against invaders?

Roman’s modest proposal had little impact when it first appeared. Yet as interest in food ethics, locavorism and foraging grew, the elegant logic of “invasivorism” hit a cultural sweet spot. In 2005 Chef Bun Lai created an invasive species menu for his sushi restaurant, Miya’s, in New Haven, Conn. In 2010 the National Oceanic and Atmospheric Administration launched its “Eat Lionfish” campaign to combat the species’ invasion of the Caribbean. In 2011 Food & Water Watch hosted an invasive species banquet at the James Beard House in New York City. In 2012 Illinois extracted 22,000 metric tons of invasive Asian carp and sold it to China, where it is commonly eaten, for $20 million.

Other projects have taken a more participatory approach: The University of Oregon’s Institute for Applied Ecology hosts an annual Invasive Species Cook-Off (aka Eradication by Mastication); Web sites such as invasivore.org—run by Matthew Barnes, a biologist at Texas Tech University—and Roman’s own site, EatTheInvaders.org, promote home recipes for exotic species. Even Whole Foods has gotten onboard; in 2016 the upscale grocer added lionfish to the shelves and started promoting it as “an invasive species” in the Atlantic Ocean and Caribbean Sea, “far from its native waters.”

Activism outruns data

But popular invasivorism has also preceded solid scientific study. “I don’t think we have the data yet to know if this is successful,” Barnes says. “There are a lot of small experiments going on but no large-scale data gathering.” What data do exist are less than conclusive. In 2013 a group of researchers from the Netherlands working on the southern Caribbean islands of Bonaire and Curaçao found lionfish biomass near Bonaire in areas where harvest was encouraged was a third of that in areas where it wasn’t and less than a quarter of what it was in the waters surrounding Curaçao, where the local government has yet to begin control efforts by harvesting. Those numbers were promising. Yet in 2016 Fisheries and Oceans Canada wrote in a report there was an “extreme” risk of Asian carp species establishing populations in three of the five great lakes within 50 years, despite millions of dollars spent by the U.S. government to build aquatic barriers and promote harvest programs. Marketing aside, most people still find the fish unappetizing.

Invasivorism can also overlook some of the complexities of ecological invasion. Different types of invasives present a variety of problems. Picking the leaves or fruits from plants such as dandelions and Himalayan blackberries does nothing to keep them from growing. Telling people they should eat Asian carp won’t make the animal appealing. And even if you could convince people to eat nutria—the South American swamp rat introduced in the 1940s to clear Louisiana’s Mississippi Delta waterways of another invasive species, water hyacinth—there’s no way they’d be able to catch up with the population, which has already wiped out entire swaths of native greenery.

There is evidence that harvesting programs could be effective if started when the target population is still small and concentrated. In their cautiously optimistic paper for the U.S. Fish and Wildlife Service, biologists Susan Pasko and Jason Goldberg noted that between the years of 1981 and 1989 the U.K. successfully eradicated a nutria infestation by incentivizing trappers, although they don’t mention whether or not anyone ate the animals. Yet a similar program targeting invasive minks failed just a few years later because that animal had already dispersed too widely. “Incentive programs can only be successful,” the authors wrote, “if the number of individuals harvested exceeds the number that would normally not survive during a single breeding cycle.” For Caribbean lionfish, that might require removing up to 65 percent of the species. With plants, those numbers are even higher.

The worst-case scenario of invasivorism is not that it won’t work, rather it will make a troublesome species popular. Martin Nuñez, an ecologist at the University of Tennessee, has published several papers warning of perverse incentives to distribute economically valuable species more widely. “If you make money off a species,” Nuñez says, “then that’s an incentive to help it spread.” Consumption is one of the most powerful incentives of all. Even advocates of invasivorism like Roman and Barnes raise the same concern.

In Hawaii, for example, feral pigs run rampant. Descendants of Eurasian boars from Russia and introduced for sport hunting long ago, they cause substantial damage to indigenous habitats. Yet to eradicate them would also be to kill an important part of the island’s cultural lexicon, built around the practice of hunting and roasting the animals. Pasko and Goldberg point out it could also create new environmental problems. Feral pigs eat the flammable, invasive grasses that now cover large swaths of the islands; without them, fires could become more common and destroy more native habitat than the pigs do themselves. In the continental U.S., people continue to spread wild boars by introducing them as game. They now cause an estimated $1.5 billion of damage annually and, within 50 years, will have reached every county in the country.

The same has begun to happen with Bolivia’s paiche and on a much shorter timescale. Paul Van Damme, a biologist working on a fisheries management program called Peces Para la Vida (Fish for Life) with the Bolivian organization Faunagua, has already seen a second wave of paiche invasion. “We thought it would take 50 or 60 years for the paiche to arrive in the upper Mamoré or Iténez,” he says, referring to Bolivia’s other two lowland river systems. “But the species is already there.” This second invasion had multiple origins, among them poorly managed fish farms in Brazil where the species is also native and also overfished. Along Bolivia’s northeastern border, formed by the Mamoré, fish farmers from Brazil cross the river to purchase baby paiche to stock their farms; on a 2018 trip to the region, some fishermen told me they had thrown those juveniles overboard when they saw authorities approaching, to avoid fines for transporting a protected species. In a particular case, he says, “this one guy actually distributed the species to farmers all over the basin,” with promises of boom times for paiche meat ahead.

In the areas of Bolivia where the paiche first appeared about 25 years ago, it now accounts for 90 percent of wild catch, although it is unclear whether that’s because other fish species are gone or because local fishermen are successful in focusing on the invader. In places where the fish arrived more recently, its growing market value has drawn more fishermen to the river, increasing pressure on paiche, along with native species. In other places, Van Damme says, paiche has become an alternative to blanquillo, a native species typically fished using freshwater dolphin meat as bait. In still others, paiche has driven both local fishes and local communities away from the water entirely. Even a single invasive species in a single river system can have staggeringly diverse effects.

Fish and Wildlife’s Goldberg describes “adapting to irreversible ecosystem changes” as “a means of last resort.” For Chef Bun Lai, invasivorism is a way of “shifting our appetites” away from the unsustainable species we currently favor. Barnes and Roman see it principally as an awareness campaign—“a way to get [invasives] on people’s radars,” as Roman says. They all agree that preventing invasives from arriving in the first place is the only real solution and that invasivorism will only be an effective management tool in cases where the culprit is caught early. “Invasivorism is not going to save the planet. and it’s not going to solve all of our problems,” Roman says. “It’s a tool in the toolbox. But, boy, you gotta be careful.”

Tennessee’s Nuñez, for his part, is skeptical of the founding premise. “The idea is that if we can drive a native species to extinction by eating it, we could do the same with an invader—but it’s not obvious to me that those dynamics would be the same,” he says. “Something can be intuitive and also be wrong.”

In Las Peñitas the intuitive choice is to fish the new species away and restore the environment to its previous balance. But it doesn’t take much work to reveal the flaws in that solution. In the first place, no environment is static, and the notion of balance is, as Barnes notes, “a social construct, scientifically tough to defend.” Many local fishermen see paiche as a boon, a lucrative commodity in a region otherwise starved for resources. It is obviously preferable to preserve native species but also imprudent to ignore the economic potential a species might bring to a poor region of South America. There are plenty of incentives for fishing paiche. The question is whether they will do more harm than good.

Managing invasive species is, in the end, principally a question of managing humans. As Salazar and the many other fishermen of Las Peñitas asked out loud, time and again, “Who knows which is the worse predator—the paiche or us?”