The pirarucu is an enormous fresh water fish that is native to the Amazon River in South America. These fish can potentially grow to over 14 feet (4.2 meters), but it takes many years for them to grow to that size, and overfishing has made the maximum size in the current population closer to 10 feet (3.0 meters). They are also a heavy fish, weighing up to 500 pounds (226 kg) or even more. The fish is gray-bodied, with a rounded front and a flattened tail area. They have gills, but they tend to live in very poor quality waters with exceptionally poor oxygen levels, and because of this, they are actually air breathers that come up to breath several times every hour.
People have found many ways to use these fish. Their scales are unusually large, sometimes even reaching 6 inches (15 cm) in length, and they are very rough, so people use them for sandpaper. The pirarucu tongue, which actually has teeth growing out of it, is also used in this way. They’ve been a favorite food source for humans, partly because they’re so big, and partly because the meat supposedly has a great flavor. Natives of the area generally had a hard time killing the fish because of their size and toughness, but Europeans settlers had better equipment and were able to handle them.
When hunting, the pirarucu has an advantage because there isn’t much oxygen in its habitat area. It comes up for air, but other fish don’t, so the other fish move around slowly while the pirarucu moves fast. They use their toothed tongue to kill their prey by crushing it against the roof of their mouth.
Many fish species have very little involvement with raising their young, but this isn’t true for this species. They dig a nest in the mud, and the female will lay her eggs there, then the male will fertilize. Both the male and the female will help each other in watching the eggs. They continue to stay after the eggs hatch, and they will defend the infants from any attempted predation. The male's head changes to a dark color during this time, which allows the babies to camouflage against his skin tone.
Many experts think that overfishing has cut the population of pirarucu significantly, but exact numbers are only a rough estimation. Local governments in its habitat area were forced to set up protections as a precaution. Pirarucu have also been kept in captivity, and some have been successfully bred there.