A GIANT FRESHWATER FISH

Arapaima gigas, also known as piraruca, or simply arapaima, is the second largest freshwater fish in the world, only exceeded by the sturgeon. Arapaima are massive yet streamlined fish that are typically 79 in (200 cm) or so in length, but reportedly can be up to 450 cm (15 ft) in length! Adults may weigh up to 440 pounds (200 kg). They are very aggressive carnivorous animals. They mainly eat other fish and also crustaceans. The fossil record of arapaima is known from as early as the early Miocene (23 m.y.a). They belong to Class Actinopterygii and family Osteoglossidae fish (Wikipedia, 2024).

Side view of an adult Arapaima gigas. The red (sometimes yellow or partly yellow) coloration is found only in the posterior half of this animal is variable in its intensity (from barely perceptible to strongly red). 

Exterior and interior views of a scale (about 7 cm long and 3 cm wide) from an adult arapaima fish. The scales are curved inward. They are used as “nail files,” and they seem to be stronger than emery boards. The scale that I have “works like a charm." Plus, they have three grinding surfaces: most of the exterior is for regular use; the wider part of the exterior is for heavy duty usage, whereas the inside of these scales have a much finer grinding surface. Also, they are quite resistant to breakage. The shoe-horn like surface can be used to remove callouses, just like a pumice stone does. The narrow end can be used to push back cuticles. They are used also for jewelry and decorations by the local tribes. These “armor like” scales have  outer mineralized layer and a tough inner layer, both of which serve as protection against pirana fish, which live in the same waters. 

Arapaima fish are native to Brazil, Bolivia, Guyana, and Peru, all of which are in the basin of the Amazon River in South America. The local name of pirarucu is derived from an indigenous word for “red fish,” probably because of the red flecks on the tail of the fish, or because of the reddish-orange color of its meat. Most of the body, however, can be silver in color, with only some red color on the tail area. 

This fish has been introduced (i.e., it is an invasive fish there) also into  parts of East Asia.

This fish is an obligate air breather, thus it needs to come to the surface to breathe. As a consequence, this fish has been heavily impacted by overfishing because it is relatively easy to catch. There are some interesting and informative videos on the “YouTube” channel showing fishermen catching this large fish. Arapaima fish are safe to eat and reportedly have a “good taste.” Their scales are coated in slime that can be difficult to remove and can also cause skin irritation.

References

Wikipedia. 2024.

YouTube videos. 2024.