Arapaima

The arapaima eats mostly other fish.

It opens its big mouth fast, and whoosh! The food gets sucked right in.

Arapaima are predators that eat mostly fish. They also eat fruits, seeds, insects, and even birds and small mammals that land on the water's surface.

To catch food, an arapaima opens its big mouth very fast. This makes a rush of water, like a vacuum cleaner, that pulls the food inside. Then it swallows its meal.

Arapaima are apex predators in Amazonian fish communities. The Smithsonian's National Zoo reports a diet mostly of fish, plus fruits, seeds, insects, birds and mammals taken at the surface. Feeding is by suction ("gulper" feeding): rapidly opening the large mouth creates a pressure drop that draws in nearby prey.

Air-breathing gives arapaima an edge in hypoxic water, where gill-breathing fish must slow down. They also make short bursts of speed to strike prey at the surface.

Every few minutes, an arapaima comes up for air.

People who know these fish sit very quietly by the lake. They count each arapaima when it pops up to breathe!

Because arapaima must come up for air, people can count them. In parts of Brazil, skilled local fishers sit silently around a lake during the dry season. They watch and listen for arapaima breathing at the surface, counting for 20-minute stretches.

These counts are surprisingly accurate. They match the results of scientific tagging studies. The counts tell communities how many fish live in each lake and how many can be caught safely.

The air-breathing habit is the basis of a census method developed in central Amazonian floodplains. Teams of up to 20 trained fishers each cover a separate part of a lake and count arapaima surfacing over synchronized 20-minute periods, using both sight and sound, and sorting fish into juveniles (1.0 to 1.5 m) and adults (over 1.5 m). Population estimates from these counts correlate strongly with mark-recapture estimates.

Counts are done only in good weather during low water, when lakes are isolated. Along the Juruá River, counts began at several lakes in 2005, and the data go to Brazil's environment agency, IBAMA, which sets a harvest quota for each lake.

People caught so many arapaima that they disappeared from some places.

Now some villages protect their lakes. They count the fish and only catch a few. The arapaima are coming back!

Arapaima have been an important food for people in the Amazon for a very long time. From the 1970s, heavy fishing made them so rare near big Amazonian cities that there were too few left to catch for sale. International trade in arapaima is controlled under CITES.

Now many communities in Brazil protect their lakes. They guard them, count the fish each year, and may catch only up to 30 percent of the counted adults. In one study along the Juruá River, protected lakes held about 305 arapaima on average, while lakes open to anyone held only about 9. Arapaima are also farmed in Peru.

The IUCN lists A. gigas as Data Deficient, from a 1996 assessment marked as needing updating (it was listed as Vulnerable in 1986 and 1988). It is on CITES Appendix II. The Smithsonian's National Zoo reports that overfishing from the 1970s made it commercially extinct near major Amazonian cities, and that it is farmed in Peru.

Since 1999, fishing accords in Brazil have grown into community-based management. Communities guard protected lakes, count arapaima annually, and IBAMA authorizes a harvest of up to 30 percent of counted adults. Across 83 Juruá River lakes, Campos-Silva and Peres (2016) found that protected lakes held 304.8 arapaima on average versus 9.2 in open-access lakes, and that management explained 71.8 percent of the variation in population size, while also bringing communities an average of US$10,601 a year.