A traditional fishing technique has been incorporated into a scientific study of the fish of the Amazon basin.
The rivers of Amazonia are not blank expanses of brown water. Trees from the rain forests that line the bank fall in frequently, and their rot-resistant tropical wood is smoothed by the river’s flow into sculptural shapes that jut from the water. University of Chicago graduate student Sebastian Heilpern was first inspired to study the role of this wood in the river ecosystem when he was looking for a particular fish species with a guide from the Yine group of indigenous Amazonians. “He said, they are always next to the wood,” Heilpern recalls.
Heilpern is also interested in what happens when fish diversity in the river changes. So to test both effects, he set up a series of plots in the Manu River, alongside the famous Cocha Cashu Biological Station, where he is researching freshwater ecology on a National Geographic Young Explorers grant. Some sections of the river were fenced off with chicken wire to keep out large fish. Others had wood added or removed, and some had no modifications at all.
But he had trouble checking on his plots. What fish were in each area? He planned to sample with a gillnet, but came up empty handed. In other field sites, he might use electrofishing, in which a mild electric current is used to knock fish out for easy collection. But there’s no way he could electrofish at such a remote location, so far from the electrical grid.
The Machiguenga people, another indigenous group who live in the Peruvian Amazon, catch and eat a lot of fish, particularly in the lean dry season. So they have a vested interest in Heilpern’s work. One leader, Mizairo Enrique, from the community of Maizal, offered to help.
Enrique learned from his father and grandfather a special fishing technique. He plants a special plant, called barbasco. After four years, its roots are large and toxic enough to stun fish. Using rocks traded from elsewhere for use as tools—as the local area has no stones—Enrique mashed the root into pulp, then waded into the Manu and wrung out the mass upstream from Heilpern’s plots, while Heilpern and an assistant waited below with a net.
The technique is not traditionally used on large rivers, but on smaller streams on ceremonial occasions. Used too often or carelessly, it can be a conservation concern; barbasco is powerful stuff.
The team fished this way twice, once at night, under a sky crowded with stars and marked by the milky way, and once early in the morning when dawn chorus of tropical birds was in full swing. Each time, they hauled up nets of stunned fish from the plots, which they carefully collected in buckets for analysis.
Through a double translation—Machiguenga to Spanish and then Spanish to English—Enrique spoke about his concerns about fish dying and disappearing from certain areas. “I want to be able to tell my children and future generations what is going on with the fish,” he said.
Up to 29 percent of the Amazon basin is under freshwater at any given moment, but little research has been done on the rivers, lakes and floodplains of the great rainforest, Heilpern says. The results of his study won’t be final for another year.
“These people know so much about the way animals work in the forest and the rivers,” Heilpern says. “Fishing is in their blood and they are born with a net in their hands. It makes sense for researchers to work with them and act as a bridge to bring their knowledge to the scientific community and vice versa.”
Emma Marris is an environmental writer based in Klamath Falls, Oregon. Her 2011 book, Rambunctious Garden, explored how conservation strategies will expand in a world increasingly impacted by human activities.