Temporal range: Miocene - recent
Not evaluated (IUCN 3.1)
C. H. Eigenmann & C. H. Kennedy, 1903
(G. Cuvier, 1818)
The tambaqui (Colossoma macropomum) is a freshwater species of serrasalmid. It is also known by the names black pacu, black-finned pacu, giant pacu, cachama, gamitana, and sometimes as pacu (a name used for several other related species).
Distribution in Brazil
The tambaqui is located all throughout Brazil and even though they can be found in different locations in Brazil, all of the tambaqui do not have a genetic diversity. 
It may reach more than 1 m (3 ft 3 in) in total length and 40 kg (88 lb) in total weight.
It is similar in shape to the piranha and is sometimes confused with the carnivorous fish; the tambaqui is tall and laterally compressed with large eyes and a slightly arched back. Body color is basic black to gray with spots and blemishes in its midbody. All the fins are black and the pectoral fins are small. Around 10% of a tambaqui's weight is fat. The world record recognized by IGFA belongs to the Brazilian Jorge Masullo de Aguiar with 32.4 kg (71 lb).
This species is usually solitary. Adults stay in flooded forests during the first five months of flooding, and consume fruits and grains. Young and juveniles live in black waters of flood plains until sexual maturity. The tambaqui feeds on zooplankton, insects, snails, and decaying plants. The species plays an important role in dispersing seeds from fruits.
Tambaqui is a fish that lives in freshwater. Salinity up to 10gL causes an effect in their hematological parameters. Their freshwater cannot have more than 15gL of salinity before tambaqui start to die. Salinity above 15gL causes there to be a change in weight, consumption, and growth rates. 
When there is not enough oxygen in the ocean, tambaqui obtain oxygen from the air. They are able to do this by their physical and inner body parts, such as their gills and swimbladder vascularization. 
Tambaqui consume fruits and seeds. 78-98 percent of their diet consists of fruits such as woody angiosperms and herbaceous species. Depending on the quantity and food quality of these foods, it causes the fish to decide on their location of their habitat. The continued destruction of the Amazon flood plants habitat is destroying the tambaqui's food source and leading to the death of more tambaquis. It is recommended to feed tambaqui two times a day. 
The fruit seeds that fall in the water are consumed by Tambaqui and the seed is dispersed somewhere else; this is similar to what birds do. This consumption includes about 35% of the trees and lianas during flood season and these seeds can grow after the floodwater calms down. Compared to the younger and smaller tambaqui, larger and older tambaqui are able to disperse the seeds in a faster rate. 
Low pH Resistance
In an experiment, tambaqui had the pH of their water changed. No deaths occurred to tambaqui fishes if the pH did not reach 3.0. The only internal difference that was noted in tambaqui fishes, when the pH was being altered, was a change in the acid-base of the plasma and red cells. 
Relationship to humans
In Thailand, this fish, known locally as pla khu dam (ปลาคู้ดำ), was introduced from Hong Kong and Singapore as part of fish-farming projects, but has adapted to local conditions and thrives in the wild in some areas. In Brazil, tambaqui is one of the main fish species that is farmed. So, tambaqui is important towards Brazil's economy. 
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- Colossoma macropomum introduced to Thailand
- Oeda Rodrigues, Ana Paula (2014). "NUTRITION AND FEEDING OF TAMBAQUI (Colossoma macropomum)". Boletim Do Instituto De Pesca 40 (1): 135-145.
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