Let´s meet the arapaima gigas, pirarucu or paiche, which are known for having a large size, and inhabit the lakes and rivers of the Amazon.
This genus belongs to the Arapaimidae family, and they are considered living fossils, being in fact some of the oldest freshwater fish in the world. Moreover, they also belong to a primitive group of carnivorous bony-tongued fish: the Osteoglossidae.
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The species is among the largest known freshwater fish, as they commonly measure 200 cm, and even exceptional lengths of up to 450 cm in some cases. The adult specimens weigh around 200 kg. The arapaima gigas have an aerodynamic and even peculiar shape, since the front of their body is long and narrow, while the back is flat and have only a rudimentary and rounded tail.
Their body color is mainly gray to gray-green, and their name «pirarucu» (of Brazilian origin), derives from an indigenous word for «red fish», which is thought to refer to the red spots on the scales of their tail, or the reddish orange color of their flesh when cooked.
Interesting facts about the Arapaima Gigas
- The Arapaima gigas need to breathe air, so they have to surface every 10 to 20 minutes. This behavior is mainly due to the low levels of oxygen in the Amazonian rivers, which led the fish that inhabit there and lack adequate lungs, to evolve a special tissue in the swim bladder that processes oxygen. Only the very young pirarucus have functional gills. We invite you to read our article the anatomy of fish, to learn about fish that breath through gills.
- The Amazonian people use the huge tongues of the dry piraruru fish, as seed- graters.
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Until the appearance of human beings on their habitat, the arapaima was one of the main predators of the Amazon River. No other species dared to attack them, since their hard but flexible scales protect them, and can´t even be penetrated by piranha’s teeth. Their scales are so effective that engineers are studying possible modern applications for them.
The secret relies in combining a highly mineralized outer layer with an internal design that makes their scales quite resistant. According to the leading researcher (Marc Meyers, a professor at the Jacobs School of Engineering at UC San Diego) the mixture of materials is similar to the hard enamel of a tooth deposited on a softer dentin.
However, their need to surface to get air, made the arapaima gigas very vulnerable to human beings since tens of thousands of years ago. This species is a vital source of protein, which makes them a prized catch for both local fishermen and chefs abroad. As for their skin, it is commonly used like leather for manufacturing clothes and artisanal arts.
Reproduction and Life Cycle
This species carries out the oral incubation, (the parents lodge the young in their oral cavity for long periods) and also their reproduction has adapted to the huge fluctuations of their environment. The pirarucus lay their eggs between February and April, when the water level is low. Then in the flood season (when the water level rises), during the months of May to August, the eggs hatch, and so they have more water to develop.
Both parents take care of their offspring when it is born, and accompany them and take them to feeding sites. The young feed on small invertebrates and plankton. The pirarucus accumulate large reserves of fat during the summer, which are very useful when they become parents. As the rainy season approaches, both sexes excavate a hole 50 cm wide and 20 cm deep in shallow water mud, using their lower jaw, fins and mouth. There, a large female can deposit up to 50,000 eggs, which are then fertilized by the male.
Subsequently he will take care of the nest while the female stays close to ward off the predators. Young newborns remain close to the father’s head, (oral incubation) which turns a grayish black color to help camouflage their young. When the young grow up enough to fend for themselves, the father swims and his head loses its dark color.
In the past, the species was greatly affected by overfishing, due to its habit of surfacing regularly to breathe. For this reason its fishing was banned in Brazil since 2001, although it is believed that the illegal fishing of arapaima gigas continues. But there is good news since many communities have developed their own fishing rules for arapaima, including banning the gill nets and establishing minimum sizes for their catches, which has resulted in the recovery of their population.
IUCN has not assigned a conservation status to the arapaima fish due to the lack of detailed information on the evolution of its population.
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