Arapaima

Arapaima battle analysis

In a warm, still Amazon lake at low water, the oxygen can run so low that most large fish cannot cope. The arapaima can. Every ten to twenty minutes it rises, gulps air with an audible splash and sinks again. Between breaths it hangs near the surface or among flooded trees, waiting for smaller fish to come close. Then its huge mouth opens so fast that water and prey rush in, and the prey is crushed against the toothed "bony tongue" and palate.

The arapaima's scales are one of the best-studied natural armors. Engineers testing them found a hard mineralized outer layer over a flexible base of collagen fibres stacked like plywood, and a piranha tooth driven into a scale broke before it could get through. Those scales let a large fish share its lakes with shoals of piranhas. They are not proof against everything: caimans share the same lakes, and a crushing crocodilian bite or a fisher's spear is a different problem from a piranha's cutting teeth.

In ABS terms the arapaima is a large, well-armored fish with modest weapons. Its Defense is solid because its armor is scientifically demonstrated, its Attack is low for its size because suction feeding does little to big opponents, and its Special reflects air breathing and remarkable parental care. Its story also includes one of conservation's success stories, as fishing communities that count the fish at their breathing rises have helped several populations recover.

Habitat & range

Arapaima live in the Amazon basin in Brazil, Peru and neighbouring countries, in floodplain lakes, slow rivers, flooded forest and swamps. Populations also occur in Guyana, and introduced populations exist outside South America, including in Indonesia where the species is considered invasive.

Diet & hunting

Adults are mainly piscivorous, taking other fish, and also eat crustaceans and occasionally birds, frogs, small mammals and plant matter. As one of the largest predators in floodplain lakes, the arapaima is itself hunted mainly by people; caimans also live in the same lakes.

Social life

Adults are usually solitary. During breeding a male and female pair, and the male guards the brood. Young fish school tightly around the guarding parent as rising water carries them into flooded forest or savanna.

Conservation

Arapaima gigas is listed as Data Deficient on the IUCN Red List. Overfishing has caused severe local declines in parts of the Brazilian Amazon, and a 2020 review called the species endangered in its native range in Brazil while invasive in Indonesia. Community-based management has produced striking recoveries: at the Mamirauá reserve, fishers counting arapaima at their breathing rises helped the population grow about nine-fold, from roughly 2,200 to 20,650 fish, between 1999 and 2006. Similar recoveries have been reported on the Juruá and Purus rivers.

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