The tambaqui ( Colossoma macropomum) is a large species of freshwater fish in the family Serrasalmidae. It is native to tropical South America, but kept in aquaculture and introduced elsewhere.
The tambaqui is currently the only member of Colossoma, but the Piaractus species were also included in this genus in the past.[OPEFE (27 December 2011). Genus Piaractus. Retrieved 2 March 2017.]
Distribution
The tambaqui is native to freshwater habitats in the
Amazon Basin and
Orinoco basins of tropical South America.
[ In nutrient-rich whitewater rivers such as the Madeira River, Juruá, Putumayo River (Içá) and Purus River it ranges throughout, all the way up to their headwaters.][Araujo-Lima, C.A.R.M.; and M.L. Ruffino (2003). Migratory Fishes of the Brazilian Amazon. Pp. 233—302 in: Carolsfeld, J.; B. Harvey; C. Ross; and A. Baer (editors). Migratory Fishes of South America. ] In nutrient-poor such as the Rio Negro and clearwater rivers such as several rightbank tributaries of the Madeira it generally only occurs in the lower c. and is rare beyond the lowermost c. .[ It is widely kept in aquaculture outside its native range in South America.][
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Middle Miocene-aged Fossil of C. macropomum are known from northern Colombia and the Peruvian Amazon. Their occurrence in Colombia suggests that prior to further uplift of the Andes, they also inhabited western South America.
Description
The tambaqui is the heaviest characin in the Americas (the lighter Salminus can grow longer) and the second heaviest Fish scale freshwater fish in South America (after the arapaima).[ but a more typical size is .][ The largest caught by Fishing rod-and-Fishing reel and recognized by IGFA weighed ,][
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It is similar in shape to the piranha and juveniles are sometimes confused with the carnivorous fish; the tambaqui is tall and laterally compressed with large eyes and a slightly arched back. Unlike more predatory species, the teeth of the tambaqui are molar-like, an adaption for crushing plant seeds and nuts.[ The lower half of its body is typically mainly blackish. The remaining is mainly gray, yellowish or olive, but the exact hue varies considerably and depends in part on habitat with individuals in blackwater being much darker than individuals from whitewater.][ The Pelvic fin, Anal fin and small are black. The tambaqui resembles the Red-bellied pacu ( Piaractus brachypomus), but the latter species has a more rounded head profile (less elongated and pointed)]
Hybrids between the tambaqui and the similar Piaractus (both species) have been produced in aquaculture,[ The hybrid offspring can be difficult to identify by appearance alone.][
File:Replica of Pacu (Tambaqui) skull by Bone Clones.jpg|Replica of Pacu (Tambaqui) skull at the San Diego Zoo
File:Pacu shedd.jpg|Specimen at the Shedd Aquarium
File:Colossoma macropomum 01.jpg| Colossoma macropomum, Zoo Leipzig
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Ecology
Habitat, breeding and migration
This species is mostly solitary,[ but it Fish migration in large schools.][ During the non-breeding season, adults stay in of white (várzea), clear and blackwater (igapó) rivers.][ They stay there for four to seven months during the flood season, but as the water level drops they move into the main river channels or to a lesser extent floodplain lakes.][ At the start of the next flood season, large schools move into whitewater rivers where they spawn between November and February.][ The exact spawning location in the whitewater rivers is not entirely certain, but apparently along woody shores][ or grassy .][ The schools then break up as the adults return to the flooded forest of white, clear and blackwater rivers, and the annual pattern is repeated.][ Larvae are found in whitewater rivers, including the Amazon River itself.][ Juveniles stay near in floodplains and flooded forests year-round, only switching to the adult migration pattern when reaching sexual maturity.][ Maturity is reached at a length of about .][
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The species regularly reaches an age of 40 years and may reach up to 65.[
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Oxygen, salt and pH resistance
When there is not enough oxygen in the river or lake, tambaqui obtain oxygen from the air. They are able to do this by their physical and inner body parts, such as their gills and swim bladder vascularization.
Tambaqui is a fish that lives in freshwater. Juveniles can survive in brackish water when the salinity is gradually raised. Salinity levels above 20 g/L result in death.[
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In an experiment, tambaqui had the pH of their water changed. No deaths occurred to tambaqui if the pH did not fall to 3.0. The only internal difference that was noted in tambaqui when the pH was being altered was a change in the acid-base of the Blood plasma and red cells.
In another experiment, tambaquis were exposed to pH drops from 6.0 to 4.0, similar to what they would encounter in their natural habitat. Researchers found that the microbial communities of the tambaqui fish gut were very resilient to the pH drops, which could explain part of the ability of tambaquis to migrate between black and white water streams in the Amazon.
Diet
Tambaqui consume fruits and seeds, especially from woody 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.[ Another study of the stomach content of 138 specimens during the high-water season found that 44% of the weight was fruits and seeds, 30% was zooplankton and 22% was wild rice.][ Among 125 specimens during the low-water season, a higher percentage had empty stomachs (14%, about ten times more than in the high-water season) and about 70% of the total stomach content weight was zooplankton.][ In addition to seeds, fruits, wild rice and zooplankton, smaller levels of , , , small fish, filamentous algae and decaying plants are consumed.][
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Seed dispersal
The tambaqui plays an important role in Seed dispersal.[ In general, more seeds are able to pass undamaged through the Red-bellied pacu ( Piaractus brachypomus) than the tambaqui, meaning that the former overall is a more efficient seed disperser.][
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Relationship to humans
The meat of the tambaqui is popular and fetches top prices in fish markets in its native range.[ It is marketed fresh and frozen.][
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Wild populations of the tambaqui have declined because of overfishing and many currently caught fish are juveniles.[ In Manaus alone, the landings fell from c. per year in the 1970s to in 1996.][ Based on a review by IBAMA, it was the 11th most caught fish by weight in the Brazilian Amazon in 1998 (just ahead of the closely related pirapitinga, Piaractus brachypomus).][
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The tambaqui is now widely kept in aquaculture. It can live in oxygen-poor waters and is very resistant to diseases.[
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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.[ but only those in the warmest regions can survive.]
Juveniles long, sometimes labelled as "vegetarian piranha", are frequently seen in the aquarium trade, but they rapidly grow to a large size and require an enormous tank.[
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