/ 
A non-native species
The arapaïma, also known as paiche in Bolivia, is not native to this country. It was introduced in the 1970s following the overflow of fish ponds in Peru. Endowed with a formidable capacity for adaptation, it rapidly colonized a large part of the Bolivian Amazon basin. The arrival of this formidable predator is not always welcomed by local populations.
Description
The paiche has an elongated, spindle-shaped body, flattened laterally on the rear third. It can reach over 2.50 meters in length and weigh over 200 kg. Its head is massive, bony and slightly rounded at the front, with eyes set far forward, giving it excellent vision of its surroundings. Its protracted, upward-facing mouth is lined with small teeth that prevent prey from escaping. The pectoral fins are located just behind the head, while the pelvic fins are positioned far back, almost level with the anus. The perfectly symmetrical dorsal and anal fins, combined with a short, rounded tail, provide powerful propulsion.
Its thick scales form a veritable armour, capable of resisting the teeth of most predators. Their color varies from green-gray to black on the back, lightening on the flanks, and turning bright red near the tail, especially during the breeding season. Sexual dimorphism is only visible at this time: males sport a flamboyant tail, while females have a duller one. The arapaima's most distinctive feature is its swim bladder, which has evolved into a primitive lung, enabling it to breathe air. This adaptation gives it a distinct advantage in oxygen-poor waters, particularly during the dry season.
Power supply
The arapaïma is an opportunistic carnivore. Its basic diet consists of fish, but it is also capable of capturing anything that falls into the water: birds, amphibians, small mammals... It is a stalking hunter. Its morphology is ideal for immobility and lightning starts. It can remain motionless for long minutes, hidden close to vegetation, waiting for prey to come within range. Its attack is extremely fast, ending with a great suction. However, it quickly runs out of steam: if its attempt fails, it generally does not pursue its target.
Reproduction
The reproduction of the arapaïma is still poorly documented, but it is known to reach sexual maturity at around 4 to 5 years of age. A female can produce between 4,000 and 10,000 oocytes. Reproduction takes place during the dry season. At this time, pairs form and dig a nest in calm, shallow areas of lakes or rivers. The pair protects the nest until hatching, and the male continues to play an essential role in keeping the fry close to him and guiding them to food. When the rainy season begins and the rivers overflow again, the young arapaimas move into the flooded forest, a refuge rich in resources and hiding places. They will remain there until the following dry season, when they will be large enough to have no predators other than humans.
The arapaïma is a species with a formidable capacity for adaptation. Present on earth for several million years, it virtually disappeared in the 1960s. Awareness and political will have succeeded in restoring populations in many countries. The pheasant remains a fragile fish in some areas. This living fossil is halfway between aquatic and terrestrial species.
