Arapaima is a genus of giant air-breathing bonytongues, within the broader Osteoglossiformes, native to the Amazon basin - the atlas's 4 species are recorded from Brazil and Peru. They are among the largest exclusively freshwater fish in the world, with atlas size figures spanning an extraordinary range from under a metre at maturity to reported lengths around 15 ft for the biggest individuals. Arapaima are obligate air-breathers, surfacing regularly to gulp air into a highly vascularized, lung-like swim bladder that lets them survive the low-oxygen, seasonally flooded lakes and varzea channels where they hunt.
The genus was long treated as a single wide-ranging species, but recent taxonomic work has split it into several distinct species across the Amazon; reflecting that recent split and the difficulty of surveying such a large, wide-ranging fish, all four species in the atlas are currently assessed Data Deficient rather than given a firm conservation status. Arapaima are a major traditional food fish across the Amazon basin and have been heavily overfished in accessible areas, driving community-based management programs that monitor spawning aggregations and set local harvest quotas. In the aquarium world they appear almost exclusively in large public aquariums and specialist giant-fish keepers rather than home tanks, given the enormous adult size, though juveniles are occasionally sold small to the exotic pet trade.