The Rio Negro (2400 km) is the largest blackwater river in the world, home to the vast Anavilhanas archipelago, made up of more than 400 islands. Its characteristic black colour is due to the breakdown of vegetation from the jungle. Because of differences in the speed of the two rivers, at its confluence with the Amazon, the waters of the Rio Negro and the Amazon do not mix but run instead side by side for more than 80 kilometres. This phenomenon is called the Meeting of Waters. Another curious peculiarity can be observed in the upper course of the Rio Negro – bifurcation of the stream, which means that the river flows in two opposite directions throughout the year.
The shallow, clear waters of the smaller tributaries of the Rio Negro are home to many small, brightly coloured fish species – the neon tetra, the angelfish, the discus and many others. Known in Europe as aquarium fish, a large portion of these fish, captured for the international market, die during transportation. Aquarium fish are most often captured in flooded undergrowth. A perfect spot would be a fallen tree with branches sprawled across the water.
My personal method is to block off a small section of the river with my shirt having tied its sleeves beforehand, then to pull the wet shirt out with a swift movement. Most often there will be several specimens in its folds.