After the beluga (European sturgeon), which can grow to more than five meters (16 feet) in length and weigh more than six hundred kilograms (1300 pounds), the Amazon basin’s paiche (Arapaima gigas) is the world’s second largest freshwater fish. It can grow to more than 2.5 meters (8 feet) in length and weigh in excess of two hundred and fifty kilograms (550 pounds). Also known as the pirarucu (an indigenous name meaning “red fish”), this massive fish inhabits the Amazon basin, and its range extends from Venezuela to Guyana, French Guiana, Surinam, Brazil, Colombia, Ecuador and Peru. It is present in southeastern Peru’s Madre de Dios region and is protected within Tambopata National Reserve.
The paiche is a highly streamlined, bullet-shaped fish, long and narrow with prominent elongated dorsal and anal fins. Its scales are blackish-green, with reddish markings towards the rear half of the body, fins and tail.
The paiche feeds on fish, crustaceans and even small animals and birds which stray into the shallows of the Amazon basin lakes and rivers it inhabits. During the dry season, when rainforest lakes are cut off from other waterways, the paiche is the apex predator in such ecosystems. The paiche has adapted its reproductive cycle to the rainy season / dry season fluctuations of its Amazon habitat. It lays its eggs when water levels are relatively low, in large nests it creates in the sand or mud of riverbeds or lakebeds, and these hatch as rising water levels ensure that the young will thrive. Both parents care for the young, escorting them to feeding areas, where they feed on small invertebrates, cooperating to create a barrier by arranging themselves in a row, facing in the same direction.
In an adaption for coping with the extremely oxygen deprived waters common to the Amazon basin, the paiche is an air-breathing fish, and this means that it can be seen in rainforest oxbow lakes, surfacing in a manner more commonly associated with ocean-dwelling cetaceans. This ability to employ the blood vessels of its lung-like labyrinth organ, which opens into the mouth, in order to breathe air, means that the gigantic paiche is able to survive and even thrive in oxbow lakes like those found throughout the wetland-rich habitats of Tambopata National Reserve, which can have an oxygen content of as little as 0.5 parts per million. When unstressed, a paiche may surface every fifteen minutes or so, although when threatened it can remain submerged for up to forty minutes. Paiches only gain the ability to breathe air as they mature and their labyrinth organ develops fully.
Traditionally, the paiche has formed an important part of the diet of human groups in the Amazon forest, and overfishing across much of its range, including Peru’s Madre de Dios region, where Tambopata National Reserve and our own Tambopata Private Conservation Area are located, combined with habitat loss, has led to a reduction in its numbers. Its flesh is considered a delicacy and continues to fetch high prices in local markets, while its tongue has been used for generations in traditional medicine.