Arapaima: The Air-Breathing Amazon Giant

An arapaima is a very large, torpedo-shaped freshwater fish with a flattened, bony-plated head, an upturned mouth, and unusually large scales — big enough that individual scales are obvious from a distance. Florida FWC describes the body as generally grey to grey-green, with many scales toward the rear carrying red markings; National Geographic describes the head as copper-green and the tail and dorsal fin as red.

The other structural feature is in the mouth. Arapaima belong to the bony-tongue fishes, and the tongue itself is a bony structure covered in small gripping teeth, working against teeth on the roof of the mouth. USGS uses exactly this trait to define the group.

The dorsal and anal fins are set far back near the tail, which combined with the flat head gives the fish its distinctive silhouette. If you have a photo from an aquarium or a canal, photograph it and the app identifies it.

Arapaima are obligate air breathers. They have gills, but the swim bladder is modified into a lung-like organ lined with tissue that takes oxygen straight from the air, and the fish cannot survive on gills alone.

Florida FWC states an arapaima must surface every 10 to 20 minutes, and that the surfacing makes a large disturbance at the water's surface. National Geographic describes a distinctive cough-like sound as the fish gulps.

That adaptation fits the habitat exactly. Amazon floodplain lakes and oxbows go warm, still and oxygen-poor in the dry season, conditions that kill gill-dependent fish. An arapaima simply breathes air instead, and can survive out of water for a period because of it.

It is also what makes them easy to kill. A fish that must show itself at the surface on a predictable schedule is an easy target for harpoons and spears, and National Geographic identifies that surfacing behaviour as a direct cause of overfishing.

Arapaima scales are studied as a model for flexible armour, and the structure is the reason. A 2020 study using advanced 3-D imaging describes them as flexible dermal armour made of elasmoid scales — overlapping layers of type I collagen under a highly mineralised hydroxyapatite outer layer.

The dimensions are unusual for a fish scale. That study measured individual scale thickness at about 3.4 mm, with overlapping thickness reaching up to 9.7 mm across the body. The authors note the flexural stiffness of the scales likely plays a part in how the fish swims, not only in how it is protected.

Hard mineral outside, flexible collagen inside, heavily overlapped: that combination lets a scale take a piercing load without shattering while still letting the body bend. It is why materials researchers keep coming back to this animal.

Arapaima feed by suction, opening a large mouth to pull prey in. The diet is mostly fish, with fruits, seeds and insects taken as well, and National Geographic reports they can leap clear of the water to take birds, lizards and small primates from overhanging branches.

Breeding is tied to the flood cycle. Females build nests on sandy bottoms in the low-water season, and the male guards the eggs and young — National Geographic describes the male incubating tens of thousands of eggs in his mouth and defending them aggressively until rising water gives the young somewhere to go.

Overfishing drove big declines, and the recovery story is a management one. Brazil now runs community-based arapaima management in which local fishing communities count surfacing fish and hold quotas, and populations have improved where that is in place. Counting the fish works precisely because they have to come up to breathe.

Arapaima turn up in US waters as released aquarium and pond fish. USGS lists records from Texas in 1995, Louisiana in 2016 and Florida in 2020, most likely from aquarium releases, with foreign introductions elsewhere traced to escapes from aquaculture.

Florida FWC reports several adults found in the wild in southwest Florida but states there is no indication they are reproducing in the state. The concern is what a fish that size would do if they did: FWC notes arapaima would prey on native freshwater fish and are large enough to eat most of them, naming largemouth bass, butterfly peacock and common snook, and that air breathing could let them occupy a wide range of south Florida waters. In Bolivia, introduced arapaima are suspected of driving declines in commercially valuable native fish.

Florida regulates arapaima as a Conditional species, meaning possession is restricted to permitted uses, and anglers with a valid freshwater fishing licence may catch, keep and eat them as a management measure. FWC asks anyone who sees one to photograph it, note the location, and report it through the IveGot1 app, IveGot1.org, or 1-888-IVE-GOT1.

There are no recorded attacks in the sources we checked. Neither Wikipedia nor the Smithsonian's National Zoo describes arapaima attacking people.

The realistic risks are different:

• Leaping: Wikipedia notes arapaima may leap out of the water if they feel constrained or harassed. A fish that the National Zoo gives at up to 440 pounds and 10 feet can hurt someone in a boat or at the edge of a net
• Nest guarding: the National Zoo says arapaima nest in the dry season, between February and March, in nests about 28 inches (70 cm) long, and the male protects the young, so do not approach a guarding fish
• Handling: a large fish thrashing on land or in a boat is dangerous; if you are unsure, cut the line rather than grabbing it

The National Zoo adds that an arapaima can survive up to 24 hours out of water, lives up to 20 years, and matures at about 4 to 5 years old.

No. None of the sources we checked describes a bullet test, and "bulletproof" is not a claim scientists make. What the research does describe is armour against bites.

Wikipedia describes each scale as a hard, mineralised outer layer with a corrugated surface over several layers of collagen fibres laid in a twisted, Bouligand-type arrangement. The 2020 study cited above measured individual scales at about 3.4 mm thick and overlapping layers up to 9.7 mm. Hard outside and flexible inside, the scale resists a piercing tooth without shattering while still letting the fish bend.

That is why materials scientists study it for flexible armour. A fish scale that stops teeth is a long way from a vest that stops a bullet.

Yes, and it has long been an important food fish in the Amazon. The Smithsonian's National Zoo calls it a favourite food of Amazonian peoples. Wikipedia describes the traditional preservation: the meat is salted, dried and rolled into a cigar-shaped package that keeps without rotting, which earned it the name "cod of the Amazon".

It also reaches shops outside South America. Wikipedia reports that in 2013 Whole Foods began selling farm-raised arapaima in the US as a cheaper alternative to halibut or Chilean sea bass.

Overfishing made wild fish scarce, and Wikipedia says Brazil banned arapaima fishing outright in 1996 before community-managed quotas were introduced. In Florida, FWC allows licensed anglers to catch and keep arapaima as a management measure (see above). As with any wild freshwater fish, follow local consumption advisories.

There is no single national answer in the sources we checked; it is decided state by state. The clearest rule we found is Florida's: FWC regulates arapaima as a Conditional species, so possession is restricted to permitted uses, while anglers with a freshwater licence may catch and keep wild ones (see above).

USGS lists arapaima as a nonindigenous species with records from Texas (1995), Louisiana (2016) and Florida (2020), most likely aquarium releases, and notes that populations may not currently be present at those sites.

The aquarium supply is legal at its source in some countries. Wikipedia says Thailand's only legal breeding farm, in Nakhon Pathom Province, has exported arapaima worldwide as aquarium fish with approval from the Department of Fisheries and CITES since early 2018. Before buying one, ask your state wildlife agency whether a permit is needed, and never release one: a fish that reaches several hundred pounds cannot be rehomed easily.

More than one. For a long time all arapaima were called Arapaima gigas, but Wikipedia now lists four to five species, A. gigas, A. agassizii, A. leptosoma and A. mapae, with evidence that a fifth, A. arapaima, should be formally recognised. USGS says the genus contains five species and that the taxonomy was only clarified in 2013.

According to Wikipedia, the species most often seen and studied, including in the aquarium trade, is A. arapaima, with a small number of A. leptosoma also recorded.

Conservation status is unsettled for the same reason. Wikipedia gives IUCN "data deficient", reflecting uncertainty about populations across the Amazon basin, while the National Zoo gives Least Concern. Both agree the fish declined through overfishing and has recovered where fishing is managed.

Not the arapaima, and probably not the piranha either. By the number of people hurt, freshwater stingrays have the strongest case among the sources we checked. Wikipedia reports more than 2,000 stingray injuries a year in Colombia alone, mostly when people step on rays or fishers handle them. The stings are very painful and occasionally fatal, especially for people in rural areas who reach medical care only once symptoms are severe, and wound infections cause much of the long-term harm.

Piranhas are feared far more than the record supports. Wikipedia says they typically do not represent a serious risk: most bites are minor wounds to feet or hands, risk rises in the low-water dry season, near fishermen, and with splashing, which is why children are bitten more often, and fatal attacks are rare. In one case Wikipedia cites, about 190 people were bitten at Palmas, Brazil, in 2007, each with a single bite to the foot. The electric eel is the other fish people name; see its page for what a shock does.

In Amazon waters, shuffle your feet when wading so rays can move away, avoid swimming near fishing activity, and get medical care quickly for any sting or bite.

The Smithsonian's National Zoo keeps arapaima in its Amazonia exhibit alongside red-bellied piranhas and red-tailed catfish. Its creature feature adds several facts:

• Size: up to 10 feet (3 m) and 440 pounds (200 kg).
• An old lineage: fossils resembling arapaima found in Colombia have been dated to more than 13 million years ago.
• Feeding: a vacuum-like strike that makes a sudden, noisy gulp, eating nearly anything that fits in the mouth.
• Young fish are vulnerable: piranhas, jaguars, giant otters and caimans prey on young arapaima; for adults, overfishing and habitat loss are the main threats.
• Population trend: wild numbers fell sharply during the twentieth century; recent research suggests they may be increasing, though the Zoo says it may take time before the evidence is clear.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from, and where sources disagree we say so instead of picking one silently. Prices and rules are given with the date we checked them; they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.