The Rio Negro, a major tributary to the Amazon River, is the largest blackwater river in the world. It is the color of Earl Gray tea with an acidity between that of orange juice and black coffee. The dark, clear water of the Rio Negro meets the milky, silty Amazon near the Brazilian city of Manaus. That is where we began our voyage upstream, in a jewel box of a riverboat called Dorinha.

 

We were a crew of fish biologists, out for science and adventure. The trip was what we now call eco-tourism, a way to fund research by inviting collaborators to join an expedition and help pay for it. Our mission was to explore the distribution and abundance of tiny, colorful tropical fish that end up, not as food, but as pets in small aquariums around the globe. You've seen them in fish bowls, but the Rio Negro is where they come from.

 

Alert to sting rays and electric eels, we waded up cola-colored streams and snorkeled deeper pools, looking for tiny colorful fish among tangled roots. Every year, forests throughout the Amazon basin are flooded by rains and snowmelt from the Andes. We canoed over top of flooded jungles, cruising like birds in treetops, eye to eye with canopy dwellers. Caimans eyed us from the water's surface, scarlet macaws from above. The flooded forest feeds this ecosystem.

 

At the time of our voyage, nearly all the tiny fish you see in your doctor’s waiting-room aquarium—cardinal tetras, neon-green tetras, iridescent Heckel discus— came from a small town on this tea-colored river in the middle of the Amazon basin. This global trade offered an economic alternative to mining and deforestation, a potential way to save the river, the ecosystem, and the people who live here, as long as the harvest was sustainable.

 

Each year, this curious little fishing town would put on an elaborate celebration of their two most famous residents: tetra and discus. Two teams of fish-costumed dancers challenged each other with elaborate parade floats and choreographed histories of the Rio Negro, from its indigenous people to the Portuguese rubber trade, and of course, its fish. Music and dancing continued until dawn to celebrate the tiny fish that were the town's main livelihood. 

 

Since our voyage up the Rio Negro, most tetras and discus come from Asian aquaculture and the local aquarium fishery is being replaced by a sport fishing industry aimed at bigger fish and thrill-seeking tourists. The rise and fall of the Rio Negro continues, with the ebb and flow of hope for those who live here.