Science reports on a conservation project that’s also helping some of the poorest people on the planet — villagers along the Juruá River, a western tributary of the Amazon — by protecting a gigantic species of freshwater fish for profit and for the sake of conservation:
The project, which emerged from a collaboration between ecologists and villages on the Juruá and elsewhere in the region, has garnered international acclaim as a model for a rare accomplishment: pairing economic development and environmental protection in one of the financially poorest and ecologically richest corners of the planet. To ecologist Hugo Costa, who has been involved in the effort from its early days, the outcome is “a breath of optimism and hope.”
At the center of it all is a very big fish.
Resembling a cross between an armored tank and an enormous guppy, the arapaima, or pirarucú as it’s often known in the Amazon, can grow up to 3 meters in length and reach 200 kilograms, making it the world’s biggest freshwater fish with scales. (Some sturgeon and catfish, which are scaleless, are larger.) Its steel-gray flanks, flecked with bright red, can withstand piranha teeth. But its size and firm, sweet flesh have made it a mainstay of local diets and cultures. For decades, arapaima were harvested for subsistence and sold in places such as Manaus, Brazil, an Amazonian city of 2.2 million.
By the 1990s, many populations had been decimated by commercial fishers who swept lakes clean with gillnets. In response, in 1996 the federal government banned all arapaima fishing in the state of Amazonas, which encompasses most of the western Amazon. Yet illegal fishing and weak enforcement continued to take a toll. By the 2010s, scientists reported overfishing for arapaima in more than 90% of surveyed villages along one stretch of the Amazon River. Conditions were much the same on the Juruá, a 3200-kilometer-long tributary of the Amazon.
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The program—the product of a collaboration between local villages and scientists at the Mamirauá Institute, a nonprofit research institution that has since become part of the federal government—relies on community members to shield fish from poachers. They are aided by the arapaima’s penchant to breed in the oxbow lakes that line the river, the remnants of old river bends cut off as the meandering waterway changed course. During the rainy season the river floods the surrounding forest and arapaima spread out over the waterlogged jungle. But when water levels drop, the gargantuan fish are trapped in the oxbow lakes, where villagers can protect them by positioning a guardhouse at a lake’s outlet.
On each lake, villagers census the fish as well, slowly traversing the water in boats and waiting for the creatures to surface. The technique capitalizes on a biological quirk of arapaima: The fish breathe air, an ability that evolved between 20 million and 10 million years ago when much of what’s now the western Amazon was a massive swamp with water that held little oxygen. The fish numbers then inform how many can be sustainably harvested.
The management approach was meant to merge “scientific and local knowledge,” says Leandro Castello, a fisheries scientist at Virginia Tech who worked with veteran fishermen to develop the fish counting technique when he was at the Mamirauá Institute in the 1990s and the early 2000s.
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Working alongside an organization representing local communities, the Association of Rural Producers of Carauari (ASPROC), the scientists have recruited 60 villages that now manage arapaima along an 800-kilometer stretch of the Juruá.
Some of the lakes these villagers oversee are open to fishing by anyone. Others are reserved for local subsistence fishing. The remainder are shielded from any fishing, except for a single event each year when guardian villages can capture up to 30% of the adult arapaima in a dayslong marathon of fishing and butchering.
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In a 2021 paper in the Proceedings of the National Academy of Sciences (PNAS), Campos-Silva and colleagues documented these and other benefits. They reported that villages inside the extractive reserves surrounding the Juruá, such as São Raimundo, were much better off than villages in nearby unprotected land. Residents were more likely to have access to a school, electricity, health care, and other community resources (see graphic, below). More than half the adults in villages outside the reserves wanted to leave their villages, but just 5% inside the reserves did.
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Some of the arapaima success story might be hard to replicate. The fish is commercially valuable, easy to count, and the population bounces back quickly. It’s also relatively easy for a small group of villagers to protect it, thanks to the fish’s habit of living in confined waterways.
But anthropologist Eduardo Brondizio of Indiana University Bloomington, who studies how communities manage resources in the Amazon, sees more universal lessons. He’s struck by how the initiative embodies key elements that scholars have identified for successfully managing shared natural resources, including an alignment between local people’s interests and broader environmental goals. “The arapaima case helps us think about how something like this could be implemented in another region,” he says. “But it’s not a recipe.”