Arapaima – Freshwater Giants of South America

Ancient armored freshwater fish crushes prey with a toothed, bony tongue

Guest curator: Daniel Gurdak (SUNY-ESF)

Arapaima sp. from Guyana. Image: D.J. Stewart

Arapaima are the largest scaled freshwater fishes in the world. Known by several names, including pirarucu (Portuguese) and paiche (Spanish), they can grow to an amazing 3 m in length and weigh up to 200 kg! These tropical giants are naturally found in the rivers and floodplain lakes of Brazil, Columbia, Ecuador, Guyana, and Peru, but have been introduced to other parts of South America and around the world.

A little bit about a big fish

The groups of species found in the genus Arapaima are part of the family Osteoglossidae, an ancient group of fishes known as the “bony-tongues”.  These freshwater monsters have not changed much in the last 13 million years!  Large, powerful and covered with an armor of hard, overlapping scales, arapaima are well equipped to survive attacks from piranhas, crocodilians and even people. Arapaima are fearsome predators -prey are sucked in and crushed between their bony, toothed tongue and a bony plate on the roof of their mouth! (See the feeding video below).

Unlike most fish, arapaima need to come to the surface every 15-20 minutes to breath air. They have a weird swim bladder lined with blood vessels which works as a primitive lung. Indeed, if an adult arapaima can’t surface to breathe it will drown! Baby arapaima hatch with working gills but can only breathe under water for just over a week. In the tropics the ability to breathe air is an advantage. This is because the combination of slow moving water, high temperatures and decomposing plant material often deprive the water of dissolved oxygen.

About their ecology and behavior

Arapaima live mostly in lakes, quiet backwaters of large rivers and adjacent floodplains. The tropical floodplain is a unique ecosystem with high and low water seasons, it is neither “terrestrial” nor “aquatic”, but both and somewhere in between. Floodplain plants and animals in the Amazon are highly adapted to annual changes in water height.  For example, when water is low, fish can become concentrated in river channels and lakes. However, as waters rise (by more than 10 m in some areas), fish move into the floodplain and feast on newly available plants, fruits, and insects.

Many fish, including the arapaima, reproduce during the beginning of the high water season.  Arapaima breed along the edges of lakes and channels in flooded forests. These are no ordinary fish – they build nests by digging a hole using their mouths, sometimes brushing away nearby leaves and branches! What’s more, arapaima parents work together to protect their eggs and young throughout the flood season.

The perils of being a large, tasty fish

For people of the Amazon Arapaima are great eating. The meat has few bones, firm texture, large fillets and tastes delicious. Sometimes called the “cod-fish” of the Amazon, it can be cooked fresh or used later by freezing or salting and drying.

Traditionally, arapaima were captured by fishermen with a harpoon or a bow and arrow.  Skilled fishermen wait patiently, and strike quickly when the fish rises up to breathe. Commercial fishing for arapaima began in the early 1800’s, and since then, over-fishing, in combination with increasing habitat degradation, has caused sharp declines in arapaima populations across much of their range. The video below shows fishermen catching arapaima.

Fishermen catching arapaima in Brazil. Images: Rafael Sá Leitão Barboza.

Arapaima today

Today, arapaima are faced with continuing habitat loss and insufficient legislation for their protection. In the depths of the rainforest any regulations are tricky to enforce. As a result, arapaima are recognized on two international endangered species lists as Arapaima gigas: IUCN Red List as “data deficient” and CITES “Appendix II”. To ensure the diversity and uniqueness of this genus is preserved, much about arapaima biology and its ecological relations in the wild still needs to be discovered.

Arapaima research in action. Image: D J Stewart

Where to see arapaima

Aside from tropical lakes and rivers (and some restaurants or fish markets), arapaima can be found in public aquaria and even in some pet shops around the world.  Keep in mind they will outgrow the average aquarium and probably the average aquarium keeper within a couple of years. With enough space and food, they can grow to 1 m in just a year!

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  1. Trackback: Meet the team: Nicolas Bailly | The BioFresh blog

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