The little pet fish that saved a town in the Amazon

This is Planet Money from NPR. A couple weeks ago, Planet Money producer Luis Gallo and I found ourselves on a dark glassy river in the middle of the Amazon Rainforest. We climbed into a small canoe. Yeah. Don't tilt us. After settling in a bit David, you have to be in the middle. Wait always in the middle. We headed up river. And we're off. We were here to investigate a change that's been happening in the worldwide multi billion dollar business of pretty little fish. You know, those tropical fish you often see at the pet store, the neon colored ones, the ones that shimmer like sequins. Some of them actually come from the wild. In fact, one of the world's most popular species of pet fish is caught right here in the Brazilian Amazon. Our guide for the day is Valdez Cicada. People call him Deco. Deco says get ready for an aventura, an adventure to see what we can catch. Will you ask Deco just to tell us a little bit more about where we're going? Our producer, Luis, who speaks Portuguese, actually, he speaks a lot of languages, was interpreted. He's saying that we're going upriver to get a better sense of where the fish live because they live in shallow water. The river that we're on is called the Rio Negro, the Black River. It's one of the main tributaries of the Amazon. And for several months out of the year, the river level rises and floods the surrounding rainforest, creating this dense tropical swamp. It's like we're in the middle of a forest, but the ground is water. Totally flooded. Deco steers us through a maze of braided waterways deeper and deeper into the forest. Oh, ow. Oh, dead. Careful with the branches. So the Rio Negro is called this because the water here is actually black. It looks like we're floating on a river of black tea. For Deko, who catches pretty little fish for a living, this unique water is the reason he has a job. You see, the color comes from the plants of the jungle. As their leaves and bark soak in the river, they release chemicals called tannins that stain the water. It is literally a kind of rainforest tea. And just like regular tea, the water here is acidic. It's slightly sour. So the fish that you find here, they are adapted to this weird water. This is where they reproduce. And for a long time, the Amazon was the only place where they reproduced. Eventually, we reach a quiet darker part of the forest. Deco leans overboard and he starts flicking the water with his fingers. He tells us that is how you attract the fish. Deco is in his fifties. He's tan and compact with big bear paw hands. Has the net, he says. He dips his net into the water and when he lifts it out oh, there they are. There are about a …