This South American freshwater fish, a species of pacu, is a close relative of the piranhas and is often encountered in the aquarium trade. In its native range, it is a popular fish for human consumption. Mylossoma duriventre occur in the Amazon, Orinoco, and Paraguay-Paraná River basins in Argentina, Bolivia, Brazil, Colombia, Ecuador, Paraguay, Peru, and Venezuela. (Jégu 2003). These fish are found in soft-bottomed rivers, streams, lakes, and ponds with a pH ranging from 5 to 7.8. (Riede 2004, cited in Froese and Pauly 2011).
Rivers in the Amazon basin are commonly classified as white water, clear water, or black water based on their color, which results from different mineral and ionic composition. White water rivers are often mud-colored and rich in dissolved minerals. Different fish species may be limited to one or more types of water. In the Amazon Basin, white water rivers are thought to function as spawning grounds for many fish species, including M. duriventre, with the associated floodplains functioning as nursery grounds. Although adult M. duriventre are found in clear, black, and white rivers, larval and early juvenile have been found only in white waters. White water habitats may function as “sources” of M. duriventre that supply fish to black and clear river “sinks”, i.e., populations in black and clear rivers may be regularly replenished from productive white river populations. Mylossoma duriventre lay eggs, which then hatch into planktonic larvae. (De Lima and Araujo-Lima 2004).
Mylossoma duriventre are omnivorous . In a study of an Amazonian tropical floodplain lake, Oliveira et al. (2006) found that these fish consumed mainly fruit and seeds during the rising water, high water, and receding water periods, whereas during the low water period they consumed mainly plant material, insects, and zooplankton. Leite and Araujo-Lima (2000) studied the larval diet of this species in the central Amazon.
Reported body length for Mylossoma duriventre is 6 to 19.5 cm (Oliveira et al 2006). The longest known record is 25 cm SL (standard length, excluding tail) (Jégu 2003).