The marvelous Pirarucu (Arapaima gigas) or Paiche is one of the world's largest freshwater fish. Specimens over ten feet long were once common, but overfishing has led to smaller individuals. The one pictured here is about five feet long. They are "living fossils" belonging to the Osteoglossidae ("bony tongue") family of fishes. The "tongue" is about five inches long and bony. Its rough surface is used by natives as a rasp to smooth wood. Amazon people have many other uses for this fish. When water levels drop and oxygen diminishes, this fish gulps air. As the river dries out completely, it curls up in a ball and rests in a burrow (aestivate) until the river floods again.
This medium-size pirarucu (about five feet long) was in a basic tile-lined tank at a small zoo in Leticia, Colombia. Unfortunately, it died fairly soon after this photo was taken, suggesting this animal is difficult to keep in captivity, at least in the conditions shown in the photo.
This picture demonstrates the size of the pirarucu's scales. Note the length on the ruler, which shows this scale is about 3.5 inches long. The dark diamond-shaped portion is thick and tougheffective armor against caiman, freshwater dolphin and predatory fish. On the living fish, the pale colored part is covered by other scales. The two holes on the right of the scale were made to string the scale together with several others. This scale comes from the back part of the fish near the tail (compare with the picture above).