The Arapaima is a true giant of the freshwater world, dwelling in the Amazon River basin and its associated floodplain lakes. Also known as Pirarucu (Brazil) or Paiche (Peru), it is one of the largest scaled freshwater fish on Earth. This remarkable creature thrives due to ancient evolutionary adaptations, allowing it to survive in challenging environments where many other fish cannot. The Arapaima has become a flagship species for the region, embodying the incredible biodiversity of the world’s largest river system.
Defining Characteristics and Size
The Arapaima possesses a long, streamlined body, often reaching lengths of up to 10 feet in the wild, though sizes between 7 and 8 feet are more commonly observed today. Mature individuals can weigh over 200 pounds, with some reports detailing specimens that exceeded 440 pounds. Its appearance is striking, featuring a broad, bony head, an upturned mouth, and a dark body that fades to a reddish-orange color toward the tail.
A defining physical characteristic is its extraordinary, armor-like scales, which can measure up to four inches wide on a large fish. These dermal plates are composed of two distinct layers: a hard, highly mineralized outer layer and a tough, flexible inner layer made of collagen. This composite structure provides exceptional protection against the powerful bites of predators like piranhas. The layers are bound together, preventing cracks from propagating through the material.
Unique Respiratory Adaptations
The Arapaima is an obligate air-breather, meaning it must regularly surface to gulp air to survive the low oxygen levels in its Amazonian habitat. This dependence is due to its respiratory system, where the swim bladder has been highly modified to function as a lung. This organ features a large surface area and an extremely thin air-blood barrier, making it highly efficient at gas exchange.
The fish must ascend to the water’s surface every 10 to 20 minutes to take a breath, a behavior known as “rolling.” This allows it to survive in stagnant or flood-plain waters that become hypoxic during the dry season. Without access to the surface air, the Arapaima would drown in as little as 10 minutes.
Ecology and Conservation Status
The Arapaima is native to the slow-moving rivers, flooded forests, and oxbow lakes of the Amazon basin, where it acts as a top predator in its ecosystem. Its diet is primarily piscivorous, consisting mainly of other fish, but it also consumes crustaceans and small terrestrial animals. It captures prey using a powerful suction-feeding technique.
Historically, the Arapaima has been heavily targeted by commercial fishing due to its large size and high market value. This intense exploitation led to significant population declines across its range, with many local stocks becoming depleted or overfished. The species is listed on CITES Appendix II, and while the International Union for Conservation of Nature (IUCN) currently lists it as Data Deficient, the Brazilian government has classified it as an overfished species.
Modern conservation efforts focus on community-based management programs, which have successfully promoted the recovery of wild populations. These initiatives involve harvest zoning, where certain lakes are designated as protected or for subsistence use, and annual population monitoring is conducted by local inhabitants. Additionally, aquaculture, or fish farming, has helped to reduce fishing pressure on wild stocks, providing a sustainable source for the market.