7 Facts About Arapaima or Pirarucu

Living fossil

Arapaima is a genus of South American tropical freshwater fish considered to be a living fossil because of its archaic morphological and anatomical characteristics. It is considered one of the largest freshwater fish in the world. The Brazilians call it the pirarucu, and in Peru it is known as paiche.

More than 2 meters / 6.5 ft
Arapaima can reach a length of more than 2 meters (in rare cases greater than 2.5 meters / 8 ft) and weighs more than 100 kg. Sometimes the largest recorded length is 4.5 m / 15 ft. This data dates back to the first half of the 18th century and is not particularly reliable.

The heaviest recorded specimen weighed 200 kg. Today, specimens of more than 2 meters are rarely seen in nature.

Labyrinthine organ

Arapaima has an expanded and elongated body in torpedo shape covered with scales and a narrowing head. Scales of adult specimens can be up to 6 centimeters long. The body has characteristic red lines. It has a special respiratory structure called a “labyrinthine organ” (so-called “primitive lung”).

Arapaima in waterDelicacy
The meat of this fish is highly valued, and the local population considers it delicacy, which certainly contributes to the fact that this meat does not contain many bones. Increased demand for meat of this fish prompted arapaime farming among “ribeirinhosim”, the local Brazilian population that living on river banks. It is also very popular among sport fishermen who consider it an excellent catch.

Guttes the air

Under water it is held for about 10 to 20 minutes only and then swims towards the surface for air ingestion. This fish guttes the air using a labyrinthine organ, and that allows the use of oxygen directly from the air. In the absence of oxygen or if it is disturbed; the arapaima often sprinkle out of the water.

This fish is known to inhabit different types of Amazonian water. It can be found in the rivers Amazon and Orinoco, their tributary rivers or floodplain lakes. Obstacles to its spread are large streams and waterfalls.

An incredible armor against piranhas

Arapaima pirarucuTo survive in a river full of piranhas it is desirable that you have a very thick, or at least a strong scales. The scales of this fish consisting of layers like a spiral staircase, made of collagen and hard outer layer protected. Exposed pressure, the spiral layers rotate, overlap, and dissipate, thereby depleting the squeeze of piranha’s sharp teeth.


Each scale at the top is about half a millimeter thick hard outer layer, which lies below twice the thickness of the soft inner core, composed of spiral layers of collagen.

60 percent of the scales overlap each other, which is additional and definitive protection, as the scientists on the simulator studying the effect of the blades found that the teeth piranhas even could break through one layer of scabs, but not two.

Two men were mysteriously missing

In July 2009, two men were mysteriously missing at Lake Kenyir in Malaysia. Villagers from nearby villages claimed that they were killed by a huge arapaima fish, which is inhabited in that lake by calling it the “monster from Kenyira”. Apparently, several of them repeatedly saw enormous fish jumping out of the water.

Despite all that, arapaima is not considered dangerous to humans. Due to its size and tendency to jump out of the water if it is threatened; it may seem somewhat scary for the one who catch it. Therefore, it is not impossible to cause small boats to overturn or panic among fishermen, but no direct attack of fish has ever been reported.