Capable of growing more than 3 metres in length and 200kg in weight, the arapaima is a freshwater giant with a fiery reputation. If threatened, it may launch itself in defence, and with a rock-hard skull and scales capable of deflecting bullets, they can deliver quite the blow.
Where do arapaima live?
The arapaima is native to rivers in the South American tropics where it is also known as a paiche or pirarucu, the latter of which has mythological roots. In Amazonian legend, Pirarucu was a warrior who was said to have a black heart. Filled with spite, he was a man with murderous intent who mocked the gods when they rebuked him for his murderous deeds.
Tupã, the god of gods, was so angered that he banished Pirarucu to the water to live as a fish. There, Pirarucu swims to this day, a giant fish ready to attack anyone who enters his domain.
Tales of people being knocked unconscious, breaking bones or even killed, give credence to the myth.
What do arapaimas look like?
The arapaima has a long, streamlined body which is olive-gey in colour with flecks of red that deepen near the tail. The dorsal and anal fins are set back and propel the fish in rapid bursts, perfect for ambush hunting.
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The head is flattened, with a large, slightly upturned mouth that contains a bony, toothed tongue typical of a species that is unchanged for millions of years. They are unfussy eaters, with a predominantly carnivorous diet made up of fish and supplemented by fruit, seeds, invertebrates and even birds depending upon food availability.
Arapaima have lung-like tissue in the swim bladder and take regular mouthfuls of air from the surface to supplement oxygen levels. This enables them to survive in near stagnant water, though the gulping sound may draw attention and the meat of the fish is highly prized.
Such has been the impact of over-fishing in some parts of Brazil, that conservation teams have been formed by local people and scientists to protect arapaima from illegal poaching.
One advantage that aids population recovery is the arapaima’s extraordinary growth rate. Once spawned, the male fish will remain to guard the eggs until they hatch, whereafter the young fish are soon big enough to fend for themselves.
How big is the arapaima?
A one-year-old specimen may measure 90cm and weigh over 10kg, and arapaima reach sexual maturity within 3 to 5 years. This has made them a popular fish in aquaculture, and in contrast to their fortune across their native range, arapaima are thriving as an invasive species, particularly in other parts of South America.
Although argument remains as to the title of the world’s largest freshwater fish, the arapaima is definitely the largest scaled freshwater species, and those scales are quite the armour.
The mineralised outer surface is rendered flexible by collagen beneath, with the fibres arranged in a spiral form known as a Bouligand structure.
Although not technically bulletproof, the scales are tough enough to deflect projectiles and more importantly, are resistant to the needle-sharp teeth of piranha.
Sometimes, the most effective weaponry is founded in defence.
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